Which fuel level do you trust?

[morbid]

Don't trust any of them.

Know what kind of mileage you get (odometer and the amount of fuel you get/use) and go by that.

If your fuel gauge were to stick, break or otherwise malfunction, you're telling me you'd not know? If you don't keep track of mileage then you can't know. you could eventually guess, but you wouldn't know it was broken until you had problems or realized it when you ran out of gas.

Exactly! I always reset my trip odometer after I get gas... and fill up around 175-200 miles.

 

[Lord Stanley]

This may introduce a different consideration, but I notice a slight fluctuation after turning the car off and then back on again. For example, let's say that the gauge reads 3/4, but then I pull into a Jiffy to get some beef jerky and a pack of smokes. When I come back out and fire up the car, the gauge will generally read a touch lower, usually a needle width.

That seems to be the same thing which happens to me... The needle does not even appear to move when driving (unless I take a really long trip, or unless I accelerate/brake or corner hard, LOL), but then if I shut the car off and let it sit for a little, next time I turn it on the gauge is lower, sometimes more than a needle width for me...

 

[elraido]

This may introduce a different consideration, but I notice a slight fluctuation after turning the car off and then back on again. For example, let's say that the gauge reads 3/4, but then I pull into a Jiffy to get some beef jerky and a pack of smokes. When I come back out and fire up the car, the gauge will generally read a touch lower, usually a needle width.

Same thing here. Especially when it is closer to the 1/2 tank lvl.

But normally I drive between 270-300 miles before I fill up....and taht is normally between 11-12 gallon.

 

[Dyoel182]

I normally hit 200 miles at half tank according to the gauge. What mileage do you guys see right around there?

 

[LauraSVT]

I normally hit 200 miles at half tank according to the gauge. What mileage do you guys see right around there?

I would see that if I were staying out of traffic. I get good mileage, but with the mixed driving I often do, I'd say closer to 160-170 at half tank on the gauge under most circumstances. I typically fill up at or near 300 on the tank with a couple gallons onboard. I don't beat the car, but I have fun when I drive it, and usually see 23ish with city driving, and 26ish when more highway is involved. I am confident that 28 is easily achievable if I kept speeds closer to 60 and took it a bit easier.

Probably more than you wanted to know, but there it is.

 

[Dyoel182]

Thats great to know actually. I probably wont run it till the low fuel light again anytime soon but its nice to know it will come on as a reminder to find the closest non-ethanol station.

 

[Ray]

I would guess that the reason the gauge doesn't move so fast when driving but "updates" when you shut it off, or restart, etc, may be because of an averaging feature in the PCM, etc.

Otherwise, every time you went up a hill, down a hill, sped up, or slowed down, turned or the like it would cause the needle to swing wildly from near empty to near full (As the gasoline sloshed in the tank. I think the PCM averages the input of the float and updates the needle as an average.

Restarting/turning the car off resets the average, and the circuit "starts over" beginning with an instant reading, which cause the needle to reset to a new location.


My educated, but possibly quite wrong, guess.

 

[LauraSVT]

I would guess that the reason the gauge doesn't move so fast when driving but "updates" when you shut it off, or restart, etc, may be because of an averaging feature in the PCM, etc.

Otherwise, every time you went up a hill, down a hill, sped up, or slowed down, turned or the like it would cause the needle to swing wildly from near empty to near full (As the gasoline sloshed in the tank. I think the PCM averages the input of the float and updates the needle as an average.

Restarting/turning the car off resets the average, and the circuit "starts over" beginning with an instant reading, which cause the needle to reset to a new location.


My educated, but possibly quite wrong, guess.

Don't know. Sounds sensible enough. That said, I don't believe I've ever owned a car that had as much swing in the gauge as the Contour does, espeically when the fuel levels are lower. They must have averaged it out over a pretty wide range of values.

The gauge in my '89 Cougar XR7 has a neat feature -- you can watch it drop when you start pulling more than 10 pounds of boost. :laugh:

 

[elraido]

Don't know. Sounds sensible enough. That said, I don't believe I've ever owned a car that had as much swing in the gauge as the Contour does, espeically when the fuel levels are lower. They must have averaged it out over a pretty wide range of values.

The gauge in my '89 Cougar XR7 has a neat feature -- you can watch it drop when you start pulling more than 10 pounds of boost. :laugh:

My Regal went down FAST after the half way mark. Like 70 miles or so and it was gone....but that first half lasted forever.

 

[Dyoel182]

Otherwise, every time you went up a hill, down a hill, sped up, or slowed down, turned or the like it would cause the needle to swing wildly from near empty to near full (As the gasoline sloshed in the tank. I think the PCM averages the input of the float and updates the needle as an average.

Unless its just a weird design I doubt the fuel level sender goes through the PCM and to the warning light and gauge. I've helped megasquirt a few cars now and their gauges worked exactly the same with the ECU unplugged and sitting in the garage.