priscilla ls1

iTrader: (1)

Hey guy's I have another question, Why would I get better gas milage on A full Tank of gas to tank with less fuel? Does it have somthing to do with the fuel pump? or does the baffels get in the way of suction?

12secSS

iTrader: (30)

You actually don't, it is a misleading affect caused by the design of the fuel tank. As the level gets lower in the tank, there is less fuel by volume and this gives the false notion that you are using more gas. The center point of the fuel level gauge on the instrument cluster is actually past the half full point of the fuel tank. It is however the mid point of the hieght the sender must travel to show fuel level. The tank is shaped like a V, so when full you think you are using less gas.

Zo6Killer

Yeah, what he said. I have always noticed that in most cars the fuel gauge is somewhat "optimistic" when above a half tank. Some are worse than others, but I just adapt and get used to it.

priscilla ls1

iTrader: (1)

But I once read somwhere that you get better gas milage on a full tank to filling to halfway twice, I think they said somthing like the sucktion in the tank and the fuel pump.

Fran D

iTrader: (5)

This seems somewhat antithetical to me. You seem to be implying (or rather, those from whom you've heard) that a difficulty in fuel delivery would result in worse mileage. I can't see how this would happen. Certainly, if there was trouble in getting fuel there would be terrible performance, but probably great mileage! Even so, unless you've made some major modifications to the fuel pickup, our F-bodies are drawing fuel from pretty close to the bottom of the tank. Half the level or full shouldn't matter relative to delivery.

All else being equal, the big contributors to mileage are weight and speed. In my view, the closer I get to empty the better the mileage I get. Since, with every gallon spent, I've lost 6 pounds. I think that whatever you've heard is some bad, old-wive's tale.

Interestingly on the fuel gauge, you'll find that GM is very careful in not calling it a Fuel Volume Indicator; it is a Fuel Level Indicator. As has already been pointed out, the gauge only points out the level of the fuel (or, more precisely, the float) in the tank, not the amount. I had talked to one of the suppliers of the pots for these sensors some time back and asked them why they didn't just scale the potentiometer (since it's just a thick-film printing process) to more accurately represent the volume of fuel. They said their customer (2 of the big 3) wasn't interested and "people understood that F meant Full, E meant Empty and everything else was something in between." Oh, OK.