Last week I decided to put just 8.3 gallons in my '95 Ranger and I got a little over 200 miles. This morning I filled up and I had exactly a gallon and a half left in the tank. That seems great, but here's why I'm concerned. Whenever I fill up which is a full 16.5 gallons I usually fill up again at either 340-350 miles and at that point I always have between half a gallon to a full gallon of gas left in the tank.

Why is this? If my math is correct then shouldn't I be seeing 400 miles or more to a full tank? I always get gas at Sheetz and drive using the same pattern/routine after each fill up. My truck is a 2.3L automatic BTW.

 

Your hauling around less weight. I think every 100 pounds is 1 mpg. I know in drag racing every 100 pounds is a 1/10 in the quarter.

 

The owners manual says 400 pounds per 1 mpg. If it was 100 lbs per 1 mph, I would get about 2 mpg when I haul dirt in the summer.

Back to the original question. Your math is probably correct but your numbers are not accurate. Your not filling up a bone dry tank with 8.3 gallons. Also when your gauge says empty you should still have a bit of gas in the tank.

What I do is fill up all the way, then take and divide miles/gallons. This will give you a much more accurate number. I have a small notebook in the truck and I keep track of all my fill ups in it. If you do it this way you MUST fill the tank up all the way or it wont work.

BTW 8 gallons of gas is about 65 lbs, not enough weight to make a difference.

 

I need to point out two things for you. I was bone dry when I put in the 8.3 gallons as I drove my truck over 20 miles after the fuel light came on. I did this purposely to see how far the 8.3 gallons could get me. Second, when I fill up, I average 21-22 mpg highway and 18-19 city (winter gas). Which is pretty awful if you ask me for a 2.3L 4 cylinder pick-up with 112HP. This whole deal still doesn't add up.

 

If your truck is still running then your not bone dry......bone dry means you are COMPLETELY out of gas and your sitting on the side of the highway.

 

 

I agree. Your test is pretty much worthless as it relies on assumptions. The only way you can truly gauge mileage is to know exactly how much gas you used -- and you don't.

 

i'm finding a bigger discrepency between winter and summer gas mpg's this year.. don't know why.. but i think the winter gas now has way more than the 10% ethanol they say it does...

 

Our gas is 10% ethenol year-round.

Get scangauge. Then you can actually see what you mileage is doing live!

 

I'm still confused here. I know exactly what I get to a full tank and what I get to half a tank. So my question again is why do I get better gas mileage when I don't fill up?

 

you dont, you get the same. The reason you have a discrepancy in your numbers is because your basing your math on an assumption. When your gas light comes on you should have about a gallon left in your tank, then you have a "reserve" also. the only really way to test your mileage is to fill up all the way and the divide the gallons by miles.

 

i'm kindda with him some. When i fill it up, 80~90 mi's and i'm at half tank, but i get 215/220 mi per tank. so the weight of the gas does affect it some, but i think the design of our tanks, or at least ones like mine aren't the best for an accurate gauge reading.

 

fill up the tank to the top..burn some say a 1/2 tank then fill up and divide the miles by the gallons u put in to fill it again= mpg's (like others have said)...

but to really find out how many miles you can get out of a tank (different question) you would have to fill to the top then run until you completely are out of fuel and the engine stops.... something you might not want to do as it puts a strain on the fuel pump and the fuel filter ...
having said that some people just gotta know and that's ok too lol

personally i don't like to let the tank get below a 1/4 .. it has a potential to churn up too much junk in the bottom of the tank...

 

the weight has nothing to do with it. And you can't use the gauge to judge how much you have in your tank. I can get 125 miles and be at 3/4 tank. So do I get 500 miles to a tank. I wish.

Gas weighs about 8 pounds a gallon. We have a 22 gallon tank. 22 gallons times 8 pounds equals 176 pounds. Do you notice a drop in mileage when you have someone in the passenger seat?

 

...it's all in your head. Seems to be the case with plenty of things. LOL