I notice a definite (or what feels like) a definite drop off in performance once you get below 1/4 tank of gas. Seems like maybe the fuel pressure just isn't there. Anyone else notice that? It becomes much more evident when you put gas back in, it seems to run stronger.

Am I ?

 

I had a 1976 sunbird (v6) right after high school and I would swear it got alot happier with a full tank of gas.

I have not noticed any drop off in my 05 Mustang GT though, feels the same to me, full or beeping at me to get gas.

 

+1

 

Can't think of any logical reason why. Fuel pressure should remain consistent until the last drop unless the fuel is sloshing away from the pickup, but that would make for a pretty noticeable hiccup.

 

i feel the same way too. my stang feels much better with a full tank.
but i think it's all in my head.

maybe it isn't...

 

To me it feels faster/lighter and more responsive when its around a quarter left

 

Well there IS slightly less weight as the tank gets emptied but the real reason is that we're all just loosing our minds. Now where's my tin foil hat???

 

I'm not sure it's a good idea to be romping WOT with very little fuel in the tank. Aren't our pumps cooled by the fuel? If there isn't much fuel in there, then the pump is probably running warmer than usual?

My old camaro's pump would start howling when I got below 1/4 tank and romped on it. That was my ticket to know I needed gas

 

You're right about the fuel pump being cooled by the gas.
However, since it runs at a steady rpm, running the engine at WOT should have no direct effect on its operating temperature.

 

If you mean immediately after filling up, maybe it likes the cooler fuel, or fresher fuel if you put very little mile on your car. Otherwise

 

Yeah, in high school I felt the same way about my Hyundai Sonata... always felt like it was more eager to go when it had a full tank. Probably all in my head, though.

 

I thought i was losing it...noticed that this weekend...was low on gas...car felt lazy...almost reflashed it. I refueled...and car runs awesome...i always use Sunoco 93..got me? i dont get it

 

See, I don't get it. I think if you run your car low, down to about 1/8 tank and then immediately put at least $20 in, you'll feel it.

 

The manual for my Whipple supercharger says not to operate the car under full throttle with less than a 1/4 tank of gas because the fuel pump could collapse.

 

Could it be the fuel in the tank is warm, and when you get a new tank it is nice and cool from the underground storage tanks? Cold fuel is much more dense and energy packed than hot fuel. Just an idea.