Gumby

gas gauge readings

We have had tons of mileage threads but I wonder how your gauge reads.


It only takes 5 gallons to fill my tank half way, which is what I usually do. well to fill the other half it takes about 10 more gallons?

Like the scale increases with gas.

When I check mileage by half a tank, its seam to get great mileage.

But do it with a full tank and it looks like crap?

Run my mileage by half a tank n it looks like 25-30mpg, do it will a full tank and it come out to like 19-21 mpg.

Maybe I should just keep the tank half full but.............

CamaroManBlack

Do you have the big half-gallons/half-liters guage? That's the type that I have. I've noticed that I get a similar reading on mine....seems to be that it takes less gas to bring to to 1/2 full than it does to a full tank...but I always figured that it had something to do with the reserve capacity. However, my gas mileage also seems to work out even no matter how much gas I have in the tank, always about 25mpg (not bad for a 20-yr-old carb'd car).
I've been told by a few people that GM didn't build the greatest gas floats or guages during the 80's. They're a little bit squirrely by manufacture I guess...

Gumby

Lets try this one more time. I am still finding odd numbers here. Since gas went up I get full tanks now and the mileage isn't as good. car runs fine though.

If I put in 5 gallons and that put me at half a tank I get 135-140 miles which works out to 27-28 MPG

Fill the tank up and I got 175-180 miles to 1/2 n an 1/8th.

15 gal / 4= 3.75


3.75/2= 1.875

3.75
3.75
1.875 +
------------
= 9.375

180/9.375 =19.2MPG


half a tank I get 27-28
Full tank I get 19-20

I must be leaking or something but never smelled it.
I am the king of gas leaks.

I think it all depends on how much gas you figure you have. If just by half a tank when on E an put in 5gal the mileage is right on. Go by a full tank and its close.

But figure half a tank is 5 gal the other half is 10, do the math right at half a tank and it doesn't seam right.

I don't know. It just nuts. I know it get good mileage but a full tank goes to fast. Or maybe when I add 5 gal to get to half, its really 6-7?

I don't know. I guess all in all I'm trying to justify plating and insurance on the Buick for 16-18MPG.

CaliCamaroRS

Think of the thirdgen gas tank as an upsidedown triangle. Then picture a horizontal line directly across the middle of the triangle, cutting it into a lower half and an upper half. The upper half is a lot larger that the lower half.

This is why the 1st half tank lasts so much longer than the 2nd half tank. I used to get about 130 miles out of the first half, and 80 miles out of the second half.

Project: 85 2.8 bird

also remember, when you fill up your tank, your car is lugging around THAT much more weight than a 1/2 tank of gas. Just keep your tank 1/2 full unless your going on road trips, when it will come in more handy.

And yes, on everysingle car I've eve owned, domestic, import, or f*rd, on a full tank, the first half of a tank lasts about twice as long as the second half.

TekViper

gas gauges are not linear, and for a reason. car makers purposely design the gauge to read so that it takes longer for the needle to move for the first half of the tank then it does the second half of the tank. they do this to give people the impression of "better" gas mileage. people fill the tank up and they see that in a day or two of driving the needle has barely moved, so they assume its getting good mileage. i think its stupid but thats they way the car makers have designed it. same thing is true for the throttle on most american cars, its not linear. that is why you feel such an acceleration when u barely depress the gas; its not always nessacerally a lot of hp under the hood. most imported cars are not like this and this is part of the reason why people used to driving american cars think that imports are lacking hp because they need to push the pedal down farther. ever notice on an american car theres barely any difference between 60% throttle and 100% throttle?

just stuff to think about

Gumby

Yea something is fishy.

Was near a tad less than 1/4 of a tank. Put in 8 gallons and was just about at full. SO by my 15 gal reasoning there is still 6-7 gallons in that last 1/4 tank and why I only got 197 miles for the first 8 gal 3/4 of a tank.

I do also do just around town driving. Lots of stop n go, so I expect a little less than ideal MPG.