Ok, so I have a 1994 F-150 XL, 300 I6, 4.9 FI, 2wd, shortbed. It's all tuned up fine. It has two gas tanks. I'm on the front one. I don't know how big it is but it takes quite a bit to fill it, unlike my Metro and the Honda I had so I figure it's big. So I go exactly 88 miles, most of it being on the freeway, no wind, and it sucked up a half a tank of gas. About how many miles to a gallon am I getting and does a half a tank seem like a lot to you?

 

To figure your gas mileage,you would need to fill your tank up and divide the gallons it took to fill it up by the miles you drove on that tank. If you wanted to use both tanks before you fill up,just use the total amount of gallons it took to fill up both tanks by the miles you drove. 88 miles doesn't seem like a lot of miles,I get more then that out of a half tank on my 11 mpg gas hog big tire f150,but I can't say for sure because I don't know how big that tank is on your truck.

 

not sure on the tank size Michelle, but i can tell you that the gas gauges in these trucks are not very accurate.
my 88 will only go around 120-140 miles before the gauge hits empty. but it will only take 7-8 gallons and that is on a 19 gallon tank.
i usually just fill it when it hits empty, unless i am out on the road, then i fill by mileage, 200 to 225 miles per tank.

 

Thanks guys .... it just seems like it's eating a lot of gas. Shoot, I drive into town and back (about 30 miles round trip) and a fourth of a tank is gone. Then this? Just seems odd that a six is that bad on gas.

 

You don't know that it's burning a lot of gas. All you know is the gauge is moving quickly. The gauge could be off. You need to record the odometer reading when you fill the tank, drive it, then record the amount of fuel it took to fill it again and the odometer reading.

(first odometer reading - second odometer reading) / number of gallons to fill it = MPG.

Anything else is just a wild guess.

 

Make sure it isn't filling the rear tank on you as well. That's a common issue with the six port switching valve, it'll keep returning fuel to one tank or the other.

 

You know what? I just remembered that the guy I bought it from told me not to freak out if it seemed like I was using a lot of gas when I was using the front tank cuz it leaks into the back one. Thanks for reminding me of that Ford six. Wow, I was going nuts thinking my favorite truck was screwing me in the wallet. I am always relieved after coming to these rooms. You guys are super. And I'm going to check the mileage use as was suggested also. Again thanks ya'll.

 

So, in case the return is not working correctly, start with both tanks topped off, draw from both tanks on your test run, then, as stated by others,

miles driven / gallons to top off both tanks = mpg

Depending upon gearing, tire size and other factors, dont be shocked if it is getting less than you expect. The 1980-1996 body has the aerodynamics of a brick and the big six, while rugged, is not particularly efficient, especially at higher rpms.

 

That filling both tanks idea sounds good but there is just one flaw in my case. One time I filled the front one all the way up, and the back one was almost filled all the way, then the front one filled the back one up the rest of the way to the point of it spilling out. So I never fill the back one all the way up now. But ya'll are super for sharing your ideas.

 

In that case, if you dont want to fix the valve, which may be too expensive, just start with the rear tank topped off, drive on only the rear tank for a good distance and top off again to do your calculation. I would use the rear tank as primary because of the return line problem anyway.

 

i agree. i would leave a few gallons in the front tank as a reserve source in case you run low, but rely on the rear tank only as your primary supply source.

 

Thanks for the great advice. I sure wish ya'll lived in my neighborhood. I'd throw a party for ya.

 

did i hear party?

New Mexico bound!!!

 

I'm glad to see that you all could come. Beers for everyone... and chips. Ah heck and Bar BQ steaks too.