Gas Tank Level Theory
I have been watching my 91 Civic's mileage particularly
closely since about October. This includes, for the overenthused, watching the fuel tank gage. A few times I have thought to myself, "Darn, it's reading just about half-full, and I usually have at least X miles by this point. The trip odometer is at more like X-50 miles right now." So I would predict that the next fillup will yield stats indicating really bad mileage. But on the contrary, apart from a few weeks where I had the timing messed up, it looks good, for winter. As people have indicated here recently, gas pumped in the summer from a nice cool underground tank (typically) expands once in the car's tank and while warming to ambient. This makes sense. In this vein, could it be that, while driving in the summer, the fuel tank gage reads particularly disproportionately to the lbs. of fuel consumed? That is, the actual level in the fuel tank goes down literally more slowly from full tank to half, because the gasoline in the tank is simultaneously expanding (due to temperature increases). By the time the driver reaches a half tank or so, the gasoline isn't expanding as quickly, because its temperature is pretty constant. I recall times in the summer where my Civic has achieved nearly 300 miles by the time the gage reads half full. Then it drops very quickly. In winter, I can't get anywhere near as many miles on the trip odometer by the time the tank is half full. Still great mileage; just totally out of whack with the fuel gage. Anyone else notice this? Comments on this theory? |
Re: Gas Tank Level Theory
Elle wrote:
> Anyone else notice this? Comments on this theory? isnt there a potentiometer in the tank operating the gauge that could be kinda wonky? |
Re: Gas Tank Level Theory
SoCalMike wrote: > Elle wrote: > > Anyone else notice this? Comments on this theory? > > isnt there a potentiometer in the tank operating the gauge that could be > kinda wonky? As Mike indicates, the fuel gage inside the tank can be bad but it could just be due to temperature in the tank. Since tank level indicators are often just wirewound potentiometers, they do fluctuate with temperature. A potentiometer is a variable resistance. Depending on the applications, they can just wire wound around a bobbin. This wire's resistance changes with temperature, depends on the wire used, etc. If the circuit that drives it fluctuates at a different rate, in a different direction or not at all, you may read different results at different temperatures. To eliminate the fuel gauge as an indicator of how much gas you are using, maybe just start a log, writing down how much you fill up, current mileage and outside temperature. Your actual MPG = (mileage reading at fill up - last mileage reading at fill up) / gallons filled with. See if this number fluctuates significantly with temperature. Remco |
Re: Gas Tank Level Theory
Elle wrote: > > I have been watching my 91 Civic's mileage particularly > closely since about October. This includes, for the > overenthused, watching the fuel tank gage. A few times I > have thought to myself, "Darn, it's reading just about > half-full, and I usually have at least X miles by this > point. The trip odometer is at more like X-50 miles right > now." So I would predict that the next fillup will yield > stats indicating really bad mileage. But on the contrary, > apart from a few weeks where I had the timing messed up, it > looks good, for winter. > > As people have indicated here recently, gas pumped in the > summer from a nice cool underground tank (typically) expands > once in the car's tank and while warming to ambient. This > makes sense. In this vein, could it be that, while driving > in the summer, the fuel tank gage reads particularly > disproportionately to the lbs. of fuel consumed? That is, > the actual level in the fuel tank goes down literally more > slowly from full tank to half, because the gasoline in the > tank is simultaneously expanding (due to temperature > increases). By the time the driver reaches a half tank or > so, the gasoline isn't expanding as quickly, because its > temperature is pretty constant. > > I recall times in the summer where my Civic has achieved > nearly 300 miles by the time the gage reads half full. Then > it drops very quickly. In winter, I can't get anywhere near > as many miles on the trip odometer by the time the tank is > half full. Still great mileage; just totally out of whack > with the fuel gage. > > Anyone else notice this? Comments on this theory? Yes, I would agree that winter vs. summer driving would see differences. However, If you are now noticing the change becoming more apparent, the sender for the gas gauge is probably starting to go. I base this experience on my daily drivers that generally forty to fifty years old and rather than trust the gauge, I simply watch the odometer and fill up at ever "x" amount of miles. There are ways to "renew" the sender but I believe that in most cases (for our purposes), it is part of the fuel pump on Hondas. Is this assumption correct? If so, better to let sleeping dogs lie than disturb it and awaken other symptoms. Regarding "renewal," I would suggest rooting around some of the antique groups for the procedure if that is what you choose to do... JT |
Re: Gas Tank Level Theory
"Remco" <whybcuz@yahoo.com> wrote
> SoCalMike wrote: > > Elle wrote: > > > Anyone else notice this? Comments on this theory? > > > > isnt there a potentiometer in the tank operating the gauge that could be > > kinda wonky? > > As Mike indicates, the fuel gage inside the tank can be bad but it > could just be due to temperature in the tank. I couldn't rule that out, sure. > Since tank level indicators are often just wirewound potentiometers, > they do fluctuate with temperature. A potentiometer is a variable > resistance. Depending on the applications, they can just wire wound > around a bobbin. This wire's resistance changes with temperature, > depends on the wire used, etc. > If the circuit that drives it fluctuates at a different rate, in a > different direction or not at all, you may read different results at > different temperatures. > > To eliminate the fuel gauge as an indicator of how much gas you are > using, maybe just start a log, writing down how much you fill up, > current mileage and outside temperature. > Your actual MPG = (mileage reading at fill up - last mileage reading > at fill up) / gallons filled with. This is what I've been doing for a couple years or so now. I'm not worried about the fuel gage. Just seems to me that it does not read in direct proportion to what's in the tank, and it may be worse in the summer. > See if this number fluctuates significantly with temperature. But winter driving conditions affect mileage IMO. So I get pretty consistently above 40 mpg in the summer, and sometimes 39 mpg or so in winter, or maybe right at 40 mpg. It definitely declines in cooler weather, but IMO that's due to all the usual reasons much discussed here. |
Re: Gas Tank Level Theory
"Grumpy AuContraire" <Grumpster@GrumpyvilleNOT.com> wrote
> Elle wrote: > > > > I have been watching my 91 Civic's mileage particularly > > closely since about October. This includes, for the > > overenthused, watching the fuel tank gage. A few times I > > have thought to myself, "Darn, it's reading just about > > half-full, and I usually have at least X miles by this > > point. The trip odometer is at more like X-50 miles right > > now." So I would predict that the next fillup will yield > > stats indicating really bad mileage. But on the contrary, > > apart from a few weeks where I had the timing messed up, it > > looks good, for winter. > > > > As people have indicated here recently, gas pumped in the > > summer from a nice cool underground tank (typically) expands > > once in the car's tank and while warming to ambient. This > > makes sense. In this vein, could it be that, while driving > > in the summer, the fuel tank gage reads particularly > > disproportionately to the lbs. of fuel consumed? That is, > > the actual level in the fuel tank goes down literally more > > slowly from full tank to half, because the gasoline in the > > tank is simultaneously expanding (due to temperature > > increases). By the time the driver reaches a half tank or > > so, the gasoline isn't expanding as quickly, because its > > temperature is pretty constant. > > > > I recall times in the summer where my Civic has achieved > > nearly 300 miles by the time the gage reads half full. Then > > it drops very quickly. In winter, I can't get anywhere near > > as many miles on the trip odometer by the time the tank is > > half full. Still great mileage; just totally out of whack > > with the fuel gage. > > > > Anyone else notice this? Comments on this theory? > > > Yes, I would agree that winter vs. summer driving would see differences. > > However, If you are now noticing the change becoming more apparent, the > sender for the gas gauge is probably starting to go. I base this > experience on my daily drivers that generally forty to fifty years old > and rather than trust the gauge, I simply watch the odometer and fill up > at ever "x" amount of miles. I wouldn't say it's more apparent. I remember years ago taking vacation trips in the car and getting this amazing mileage for the first half tank, suggesting I was going to get like 600 miles out of a full tank. Then the decline would be rapid, and I'd get the usual 390-450 miles from a full tank, say. But thanks for the tip, should things ever go way out of whack. > There are ways to "renew" the sender but I believe that in most cases > (for our purposes), it is part of the fuel pump on Hondas. Is this > assumption correct? If so, better to let sleeping dogs lie than disturb > it and awaken other symptoms. Regarding "renewal," I would suggest > rooting around some of the antique groups for the procedure if that is > what you choose to do... Oh, I'm not complaining. Just wondering, since some folks have occasionally come here ISTM and asked about the accuracy of the fuel tank gage. |
Re: Gas Tank Level Theory
Elle wrote:
> "Remco" <whybcuz@yahoo.com> wrote > > SoCalMike wrote: > > > Elle wrote: > > > > Anyone else notice this? Comments on this theory? > > > > > > isnt there a potentiometer in the tank operating the > gauge that could be > > > kinda wonky? > > > > As Mike indicates, the fuel gage inside the tank can be > bad but it > > could just be due to temperature in the tank. > > I couldn't rule that out, sure. > > > Since tank level indicators are often just wirewound > potentiometers, > > they do fluctuate with temperature. A potentiometer is a > variable > > resistance. Depending on the applications, they can just > wire wound > > around a bobbin. This wire's resistance changes with > temperature, > > depends on the wire used, etc. > > If the circuit that drives it fluctuates at a different > rate, in a > > different direction or not at all, you may read different > results at > > different temperatures. > > > > To eliminate the fuel gauge as an indicator of how much > gas you are > > using, maybe just start a log, writing down how much you > fill up, > > current mileage and outside temperature. > > Your actual MPG = (mileage reading at fill up - last > mileage reading > > at fill up) / gallons filled with. > > This is what I've been doing for a couple years or so now. > > I'm not worried about the fuel gage. Just seems to me that > it does not read in direct proportion to what's in the tank, > and it may be worse in the summer. > Chances are they are not linear and probably gets worse with temperature. One project I did was for TLIs (Tank Level Indicators) for use on subs and surface fleet. The problem was that the tank readouts are notoriously non-linear and very inaccurate because of environmental fluctuations. Tanks are round, usually. NAVY tanks have stuff like pipes running thought them. So the fill curve looks like a mountain ridge - peaks and valleys. Cars are perhaps less so, but certainly they are not square boxes (an ideal linear tank) so their tank curve is not linear. It was so bad that when they were filling a tank, they'd as a rule spill oil, causing environmental problems and be fined. The NAVY is interested in filling FAST and accuracy is a distant second - remember, they can be in war like conditions. Of course, they are interested what they have left in their tanks. The standard NAVY carrier procedure to check tank level is to drop a plumb bobbin with a string into a tank, to not trust the TLI (incredible, but true). The stuff I designed alleviated that problem under most circumstances. So if the NAVY is having problems, one can only imagine how bad an automotive system is. > > But winter driving conditions affect mileage IMO. So I get > pretty consistently above 40 mpg in the summer, and > sometimes 39 mpg or so in winter, or maybe right at 40 mpg. > It definitely declines in cooler weather, but IMO that's due > to all the usual reasons much discussed here. Could be - Never looked into that. You could very well be right. In cooler weather one does run the heater/lights and nothing comes free. Of course, AC in summer costs more so one would expect summer driving to be worse, when it comes to mileage... It would be an interesting thing if we all kept track of our mileage and posted it somewhere, along with current temperature. We'd get this very large mileage database of mileage change of cars against temperature. Obviously we would not be interested in the actual mileage, but the change in mileage against temperature. (here's the scientist talking - it may not be practical :) We might find out that maybe the oil companies add something to their gas in winter or summer we don't know about. Maybe humidity of air affects the gas somehow? Just guessing... |
Re: Gas Tank Level Theory
Elle wrote:> >> snipped<< >Still great mileage; just totally out of whack > with the fuel gage. > > Anyone else notice this? Comments on this theory? The simple fact is, the fuel gauge is just that... a gauge, not a calibrated instrument, as say an altimeter would be. Now if the fuel level gauge was based on fuel trim or other engine management inputs, that would be a different story. |
Re: Gas Tank Level Theory
"Remco" <whybcuz@yahoo.com> wrote
> Elle wrote: > > "Remco" <whybcuz@yahoo.com> wrote > > > SoCalMike wrote: > > > > Elle wrote: > > > > > Anyone else notice this? Comments on this theory? > > > > > > > > isnt there a potentiometer in the tank operating the > > gauge that could be > > > > kinda wonky? > > > > > > As Mike indicates, the fuel gage inside the tank can be > > bad but it > > > could just be due to temperature in the tank. > > > > I couldn't rule that out, sure. > > > > > Since tank level indicators are often just wirewound > > potentiometers, > > > they do fluctuate with temperature. A potentiometer is a > > variable > > > resistance. Depending on the applications, they can just > > wire wound > > > around a bobbin. This wire's resistance changes with > > temperature, > > > depends on the wire used, etc. > > > If the circuit that drives it fluctuates at a different > > rate, in a > > > different direction or not at all, you may read different > > results at > > > different temperatures. > > > > > > To eliminate the fuel gauge as an indicator of how much > > gas you are > > > using, maybe just start a log, writing down how much you > > fill up, > > > current mileage and outside temperature. > > > Your actual MPG = (mileage reading at fill up - last > > mileage reading > > > at fill up) / gallons filled with. > > > > This is what I've been doing for a couple years or so now. > > > > I'm not worried about the fuel gage. Just seems to me that > > it does not read in direct proportion to what's in the tank, > > and it may be worse in the summer. > > > > Chances are they are not linear and probably gets worse with > temperature. > > One project I did was for TLIs (Tank Level Indicators) for use on subs > and surface fleet. The problem was that the tank readouts are > notoriously non-linear and very inaccurate because of environmental > fluctuations. > Tanks are round, usually. NAVY tanks have stuff like pipes running > thought them. So the fill curve looks like a mountain ridge - peaks and > valleys. Cars are perhaps less so, but certainly they are not square > boxes (an ideal linear tank) so their tank curve is not linear. Obnoxious aside: I actually do have experience with submarine tanks, but only the ones in the engine room, which were quite a bit smaller and were not being fully emptied and filled on a regular basis, or a direct reading level gage sufficed, if they were. > It was so bad that when they were filling a tank, they'd as a rule > spill oil, causing environmental problems and be fined. The NAVY is > interested in filling FAST and accuracy is a distant second - remember, > they can be in war like conditions. > Of course, they are interested what they have left in their tanks. The > standard NAVY carrier procedure to check tank level is to drop a plumb > bobbin with a string into a tank, to not trust the TLI (incredible, but > true). > The stuff I designed alleviated that problem under most circumstances. > > So if the NAVY is having problems, one can only imagine how bad an > automotive system is. Good anecdote. > > But winter driving conditions affect mileage IMO. So I get > > pretty consistently above 40 mpg in the summer, and > > sometimes 39 mpg or so in winter, or maybe right at 40 mpg. > > It definitely declines in cooler weather, but IMO that's due > > to all the usual reasons much discussed here. > > Could be - Never looked into that. You could very well be right. In > cooler weather one does run the heater/lights and nothing comes free. > Of course, AC in summer costs more so one would expect summer driving > to be worse, when it comes to mileage... Not to lecture, but there's a whole slew of other items that afaic have been reasonably proposed in the past, like the engine ECU runs the engine at idle longer or slightly more rich; the oil viscosity is higher, the air is denser so wind resistance is higher in winter, etc. > > It would be an interesting thing if we all kept track of our mileage > and posted it somewhere, along with current temperature. We'd get this > very large mileage database of mileage change of cars against > temperature. Obviously we would not be interested in the actual > mileage, but the change in mileage against temperature. (here's the > scientist talking - it may not be practical :) > > We might find out that maybe the oil companies add something to their > gas in winter or summer we don't know about. Maybe humidity of air > affects the gas somehow? Just guessing... SoCalMike and Jim Beam have pointed out that, at least in some parts of the country, the gasoline formulation for winter is different, and of a lower calorific value, than in the warmer months. Various fed and state EPA web sites back this up, as well. So for some drivers, for sure this is a factor partly explaining their lower gas mileage around winter. |
Re: Gas Tank Level Theory
Elle wrote: > "Remco" <whybcuz@yahoo.com> wrote > > Elle wrote: > > > "Remco" <whybcuz@yahoo.com> wrote > > > > SoCalMike wrote: > > > > > Elle wrote: > > > > > > Anyone else notice this? Comments on this theory? > > > > > > > > > > isnt there a potentiometer in the tank operating the > > > gauge that could be > > > > > kinda wonky? > > > > > > > > As Mike indicates, the fuel gage inside the tank can > be > > > bad but it > > > > could just be due to temperature in the tank. > > > > > > I couldn't rule that out, sure. > > > > > > > Since tank level indicators are often just wirewound > > > potentiometers, > > > > they do fluctuate with temperature. A potentiometer is > a > > > variable > > > > resistance. Depending on the applications, they can > just > > > wire wound > > > > around a bobbin. This wire's resistance changes with > > > temperature, > > > > depends on the wire used, etc. > > > > If the circuit that drives it fluctuates at a > different > > > rate, in a > > > > different direction or not at all, you may read > different > > > results at > > > > different temperatures. > > > > > > > > To eliminate the fuel gauge as an indicator of how > much > > > gas you are > > > > using, maybe just start a log, writing down how much > you > > > fill up, > > > > current mileage and outside temperature. > > > > Your actual MPG = (mileage reading at fill up - last > > > mileage reading > > > > at fill up) / gallons filled with. > > > > > > This is what I've been doing for a couple years or so > now. > > > > > > I'm not worried about the fuel gage. Just seems to me > that > > > it does not read in direct proportion to what's in the > tank, > > > and it may be worse in the summer. > > > > > > > Chances are they are not linear and probably gets worse > with > > temperature. > > > > One project I did was for TLIs (Tank Level Indicators) for > use on subs > > and surface fleet. The problem was that the tank readouts > are > > notoriously non-linear and very inaccurate because of > environmental > > fluctuations. > > Tanks are round, usually. NAVY tanks have stuff like pipes > running > > thought them. So the fill curve looks like a mountain > ridge - peaks and > > valleys. Cars are perhaps less so, but certainly they are > not square > > boxes (an ideal linear tank) so their tank curve is not > linear. > > Obnoxious aside: I actually do have experience with > submarine tanks, but only the ones in the engine room, which > were quite a bit smaller and were not being fully emptied > and filled on a regular basis, or a direct reading level > gage sufficed, if they were. > > > It was so bad that when they were filling a tank, they'd > as a rule > > spill oil, causing environmental problems and be fined. > The NAVY is > > interested in filling FAST and accuracy is a distant > second - remember, > > they can be in war like conditions. > > Of course, they are interested what they have left in > their tanks. The > > standard NAVY carrier procedure to check tank level is to > drop a plumb > > bobbin with a string into a tank, to not trust the TLI > (incredible, but > > true). > > The stuff I designed alleviated that problem under most > circumstances. > > > > So if the NAVY is having problems, one can only imagine > how bad an > > automotive system is. > > Good anecdote. > > > > But winter driving conditions affect mileage IMO. So I > get > > > pretty consistently above 40 mpg in the summer, and > > > sometimes 39 mpg or so in winter, or maybe right at 40 > mpg. > > > It definitely declines in cooler weather, but IMO that's > due > > > to all the usual reasons much discussed here. > > > > Could be - Never looked into that. You could very well be > right. In > > cooler weather one does run the heater/lights and nothing > comes free. > > Of course, AC in summer costs more so one would expect > summer driving > > to be worse, when it comes to mileage... > > Not to lecture, but there's a whole slew of other items that > afaic have been reasonably proposed in the past, like the > engine ECU runs the engine at idle longer or slightly more > rich; the oil viscosity is higher, the air is denser so wind > resistance is higher in winter, etc. > > > > > It would be an interesting thing if we all kept track of > our mileage > > and posted it somewhere, along with current temperature. > We'd get this > > very large mileage database of mileage change of cars > against > > temperature. Obviously we would not be interested in the > actual > > mileage, but the change in mileage against temperature. > (here's the > > scientist talking - it may not be practical :) > > > > We might find out that maybe the oil companies add > something to their > > gas in winter or summer we don't know about. Maybe > humidity of air > > affects the gas somehow? Just guessing... > > SoCalMike and Jim Beam have pointed out that, at least in > some parts of the country, the gasoline formulation for > winter is different, and of a lower calorific value, than in > the warmer months. Various fed and state EPA web sites back > this up, as well. So for some drivers, for sure this is a > factor partly explaining their lower gas mileage around > winter. That's very cool, being familiar with subs - Not obnoxious at all. I am not ex-NAVY. Just contracted for them at one of my previous employers and have seen the inside of subs plenty of times. By any chance, have you seen/used the digital panel meters, the ones where a sub only needs to take few spares as one indicator holds hundreds of different curves, are cloneable? That's my design. I am sure you ar eright -- the gas formulation must be different and must be affecting mileage. |
Re: Gas Tank Level Theory
"Remco" <whybcuz@yahoo.com> wrote
Elle snip > By any chance, have you seen/used the digital panel meters, the ones > where a sub only needs to take few spares as one indicator holds > hundreds of different curves, are cloneable? That's my design. Nah, I'm pretty dated. The last time I was in a submarine engine room (as a civilian engineer) was in the 1980s. |
Re: Gas Tank Level Theory
"Elle" <honda.lioness@earthlink.net> wrote in message news:uZkxf.8215$M%4.5531@newsread3.news.atl.earthl ink.net... > I have been watching my 91 Civic's mileage particularly > closely since about October. This includes, for the > overenthused, watching the fuel tank gage. A few times I > have thought to myself, "Darn, it's reading just about > half-full, and I usually have at least X miles by this > point. The trip odometer is at more like X-50 miles right > now." So I would predict that the next fillup will yield > stats indicating really bad mileage. But on the contrary, > apart from a few weeks where I had the timing messed up, it > looks good, for winter. > > As people have indicated here recently, gas pumped in the > summer from a nice cool underground tank (typically) expands > once in the car's tank and while warming to ambient. This > makes sense. In this vein, could it be that, while driving > in the summer, the fuel tank gage reads particularly > disproportionately to the lbs. of fuel consumed? That is, > the actual level in the fuel tank goes down literally more > slowly from full tank to half, because the gasoline in the > tank is simultaneously expanding (due to temperature > increases). By the time the driver reaches a half tank or > so, the gasoline isn't expanding as quickly, because its > temperature is pretty constant. > > I recall times in the summer where my Civic has achieved > nearly 300 miles by the time the gage reads half full. Then > it drops very quickly. In winter, I can't get anywhere near > as many miles on the trip odometer by the time the tank is > half full. Still great mileage; just totally out of whack > with the fuel gage. > > Anyone else notice this? Comments on this theory? > Probably the best article on the topic of "when to fill your gas tank" is discussed in the link below. It's long but easy reading. All in all, since the variance of below grade temperature is very low regardless of the ambient temperature, it almost doesn't make any difference when you fill the tank. Having said that--it's best not to do it right after the underground tank has been filled when the fuel will most likely be at its warmest. http://www.omega.com/techref/flowmetertutorial.html MLD |
Re: Gas Tank Level Theory
"MLD" <MLD@verizon.net> wrote
> Probably the best article on the topic of "when to fill your gas tank" is > discussed in the link below. It's long but easy reading. All in all, since > the variance of below grade temperature is very low regardless of the > ambient temperature, it almost doesn't make any difference when you fill the > tank. I read about this elsewhere a few weeks ago, and it seems reasonable to me. I am not particularly concerned about when I fill the tank. (If only to minimize compulsiveness!) I do get great mileage on this tiny 1.5 L engine, just about any time of year, with just about any gas station (with only an occasional rare exception). > Having said that--it's best not to do it right after the underground > tank has been filled when the fuel will most likely be at its warmest. > http://www.omega.com/techref/flowmetertutorial.html :-) |
Re: Gas Tank Level Theory
Elle wrote:
> "Remco" <whybcuz@yahoo.com> wrote > Elle > snip > > By any chance, have you seen/used the digital panel > meters, the ones > > where a sub only needs to take few spares as one indicator > holds > > hundreds of different curves, are cloneable? That's my > design. > > Nah, I'm pretty dated. The last time I was in a submarine > engine room (as a civilian engineer) was in the 1980s. Mine was around the late 80s/early 90s. Pretty amazing machines them subs, imo. |
Re: Gas Tank Level Theory
Elle wrote: > > "Grumpy AuContraire" <Grumpster@GrumpyvilleNOT.com> wrote > > Elle wrote: > > > > > > I have been watching my 91 Civic's mileage particularly > > > closely since about October. This includes, for the > > > overenthused, watching the fuel tank gage. A few times I > > > have thought to myself, "Darn, it's reading just about > > > half-full, and I usually have at least X miles by this > > > point. The trip odometer is at more like X-50 miles > right > > > now." So I would predict that the next fillup will yield > > > stats indicating really bad mileage. But on the > contrary, > > > apart from a few weeks where I had the timing messed up, > it > > > looks good, for winter. > > > > > > As people have indicated here recently, gas pumped in > the > > > summer from a nice cool underground tank (typically) > expands > > > once in the car's tank and while warming to ambient. > This > > > makes sense. In this vein, could it be that, while > driving > > > in the summer, the fuel tank gage reads particularly > > > disproportionately to the lbs. of fuel consumed? That > is, > > > the actual level in the fuel tank goes down literally > more > > > slowly from full tank to half, because the gasoline in > the > > > tank is simultaneously expanding (due to temperature > > > increases). By the time the driver reaches a half tank > or > > > so, the gasoline isn't expanding as quickly, because its > > > temperature is pretty constant. > > > > > > I recall times in the summer where my Civic has achieved > > > nearly 300 miles by the time the gage reads half full. > Then > > > it drops very quickly. In winter, I can't get anywhere > near > > > as many miles on the trip odometer by the time the tank > is > > > half full. Still great mileage; just totally out of > whack > > > with the fuel gage. > > > > > > Anyone else notice this? Comments on this theory? > > > > > > Yes, I would agree that winter vs. summer driving would > see differences. > > > > However, If you are now noticing the change becoming more > apparent, the > > sender for the gas gauge is probably starting to go. I > base this > > experience on my daily drivers that generally forty to > fifty years old > > and rather than trust the gauge, I simply watch the > odometer and fill up > > at ever "x" amount of miles. > > I wouldn't say it's more apparent. I remember years ago > taking vacation trips in the car and getting this amazing > mileage for the first half tank, suggesting I was going to > get like 600 miles out of a full tank. Then the decline > would be rapid, and I'd get the usual 390-450 miles from a > full tank, say. > > But thanks for the tip, should things ever go way out of > whack. > > > There are ways to "renew" the sender but I believe that in > most cases > > (for our purposes), it is part of the fuel pump on Hondas. > Is this > > assumption correct? If so, better to let sleeping dogs > lie than disturb > > it and awaken other symptoms. Regarding "renewal," I would > suggest > > rooting around some of the antique groups for the > procedure if that is > > what you choose to do... > > Oh, I'm not complaining. Just wondering, since some folks > have occasionally come here ISTM and asked about the > accuracy of the fuel tank gage. Gas gauges are notoriously inaccurate when it comes to a smooth range of motion regarding fill status. Most do exactly what you describe but when they reach empty, they still have a gallon or two left. I had a truck that when it was on empty, it was empty. I cannot remember the times that I ended up having to walk down the road for gas because of my preconceived notion of the "hidden" reserve. <G> JT |
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