How low to run out my gas when testing mpg?

[batstiva]

See this is the result of someone who's been driving a Cherokee for 10 years that only gets 15mpg on a good day. You find that you don't WANT to gauge your mpg because it hurts too much. Now it's kind of fun but it's a whole new ballpark for me lol.

I feel your pain, I had an 88 F-250 with the 351 before I got my 89 Stiva. I somehow felt I was better off not knowing the miles per gallon.

In answer to your other question, the tanks are rated at just over 10 gallons. Tho, I've squeezed nearly 12 in one once. And that was from flat empty. Ask me how I know.

[Zanzer]

^^ LOL

Although rated at 10; from "E" mine overflows at just past nine gallons....you don't have to ask how I know, the white paint under my filler nozzle is a dead giveaway :confused3:

[kartracer46]

I typically fill mine to just before gas starts running down the side of the car, and run mine down til about 1/4 tank. I don't compute my MPGs every time, but I pretty much always write down the mileage. Usually figure MPGs once a month, or so. Pretty much average between 43 and 45. Not bad for a carby, eh?

And +whatever number we are up to on not running it all the way out. Just asking for trouble, IMHO.

Apparently I need to see your car again and figure out what all this stuff is I can eliminate. Your carby is doing better than mine with all the junk on it.

[darrenryall]

You could always do what Mtec007 or myself are doing. Drive your car normally, then log each of your fills at a website. The one I use then calculates ongoing cumulative mileage totals per fill, per last three fills, and lifetime as measured to date. I have to convert it all over from metric (km/L <> mpg and litres <> gallons) but so far the figures I'm getting are close to what others here are getting, so I'm happy with what I'm seeing.

And if you check out the profile I have over at ecomodders, and find the Festiva there, you'll even find the drag coefficient there.

But check out both Mtec007 and my sigs for examples.. you have to keep track a bit of your odometer plus the amount of gas you pump in, but that's really about all it takes.

[JohnGunn]

You don't have to run it super-low. If you pay at the pump you can do what I do. When you fill up there's typically a fuel amount on the reciept so just make a note of the mileage on the receipt. Drive the car until the fuel gets as low as you want to run it without running out. Go fill up again, then make a note of the mileage on that receipt. Then just use the gallons used vs. miles driven from the 2 receipts to figure out your mileage. Using this method you can check it at whatever level you want.

That's what I do. The more gas you use, the more accurate your MPG calculations will be, but never run it empty.

Me too. Even though I wouldn't recommend running out of gas for the sole purpose of testing you gas mileage, I do think it is worthwhile knowing the point on your gauge where that happens. If you have a gas can, allow it to run out once and remember the point on the gauge where that happens. Maybe even take a picture of the gauge so that you can remind yourself from time to time.

John Gunn
Coronado, CA

[Evil D]

Well i ran it down to the E line and i figure most cars from the last 20 years or so have a little play room under the E. It took 8 gallons on the money and i got exactly 250 miles out of the tank. I did the math and i got 31.25mpg out of that tank of gas. I'm figuring it could be better if my choke worked...cold starts mean me having to goose the gas to keep it idling which is gonna waste some gas. Other than that, is that about average?

[Team Lightning]

I have a book I keep with me to log all fill-ups and service.
I log: Date, Price (per gallon), Mileage, Gallons used, Total price for fill-up.

[JPT]

On my Festy, hitting the "E" mark means you have used just over 8 gallons.

[Evil D]

Well my mileage is getting progressively worse. The first tank was 32, second tank was 30, third tank is now 28. Any ideas? I'm gonna be doing a tune up on it...but i don't see that being the cause of mileage drop between 3 tanks of gas, and it runs fine.

[MTec007]

(although i have been really bad about keeping track of fillups since april 11th.. maybe i will get back into it.)

tada:

[kartracer46]

I have a book I keep with me to log all fill-ups and service.
I log: Date, Price (per gallon), Mileage, Gallons used, Total price for fill-up.

The only thing I could think to add would be what Station you purchased the fuel at to see which fuel is providing you the best outcome. Shell, BP, and a few others claim that their fuel is better. But I can stop at WAWA and save 3-5 cents per gallon and get the same results, so I don't know how true all that is.

[Charlie1717]

(although i have been really bad about keeping track of fillups since april 11th.. maybe i will get back into it.)

tada:

Fuelly is pretty sweet. I just started using it a little over a month ago (notice the 2 fill ups) But you can put little notes, cost of gas, and what not which is cool. And you can set it up so you can text your miles and it will calculate your MPG and put it on your profile.

[Festiva_tunner]

Zanzer has the eaisiest way fill it and note the milage then when you fill up check how much you put in and note your milage
There are plenty of online calculators for those who hate math
Remember its a 9.2 - 9.9 gallon tank depending on what manual you look at

If you plug the cost of fuel in as well it will tell you your cost per mile
My GPS does this for me it's neat to see your trip only cost you 85 cents

[drddan]

Well my mileage is getting progressively worse. The first tank was 32, second tank was 30, third tank is now 28. Any ideas? I'm gonna be doing a tune up on it...but i don't see that being the cause of mileage drop between 3 tanks of gas, and it runs fine.

A tune up will help, especially if you put an aftermarket hi volt ignition coil on it at the same time. I did new hi-volt coil, good wires, plugs, distributor cap, rotor on mine. Went from mid 30's to over 40 mpg. Got one run on stock 12 inch tires at 46mpg.
With my wide 14 inch tires, I still get over 37 mpg.
Another is, as atmospheric conditions change, so will your mileage. Carbs are more prone to this. Some days my car will run real strong, other days, not so much. This will also effect mileage.

[Evil D]

I was under the impression that 13s on mine should net me a little improvement in mileage but that hasn't been the case. I'll do the tune up and see how it goes.