Gas / Fuel Light

[TeeWX98GST]

Well, last week I decided I'd clock my gas milage starting from when my fuel light comes on and stares at me in its horrid orange-ness . My Gas Milage has changed by alot in just 1 week and it's really scaring me. Heres the two scenario's.

Week 1:
Fuel : Premium 92 Octane
Shift Points : 3,000-3,500RPM
Use-age : Racing, Occasional 65-110 3rd gear highway pulls, Frequent showing off of my open o2 housing
Miles Per Gallon : ~25mpg

Week 2:
Fuel : Premium 92 Octane
Shift Points : 2,000-2,500RPM
Use-age : Taking It Easy, Cruising, Listening to My New Speakers
Miles Per Gallon : ~18-19mpg

What happened? I don't think I have any boost leaks, my car seems to run so well and consistant power wise. Does my car hate taking it easy or what? I really don't know what to say here. Could I have a bad o2 sensor? My check engine light is gone (the bulb itself) I just recently found out and I will need to get that replaced and checked out but in the meantime what could I expect?

 

[webconnect]

Were your driving environments the same? City/Highway, Temperature. I had a feeling this was happening to me too though.

 

[TeeWX98GST]

The only thing that really changed I geuss was the recent flooding of alot of stuff around here, it hasn't been really any more humid though. But It's been about 80 lately and I think last week it was around 70 or so. Not much of a change and I went from mostly highway/long cruises to pretty much straight city. But even on the highway it felt like I lost gas milage. I threw in $5 of 89 which got me about 1.3 gallons and after driving 20 miles my gas light came on again when I got to the gas station in that town which sells premium.

 

[SpiralOut]

It could be the gas too, Alot of times water will get into the tanks and give you bad milage. So go try putting in a fresh tank of some better gas.

 

[Defiant]

Well, last week I decided I'd clock my gas milage starting from when my fuel light comes on and stares at me in its horrid orange-ness

Well, that's pointless as all hell. My light comes on sometimes 100 miles into a tank, and other times not at all.
To figure gas mileage, use your trip meter or your odometer. "Miles Per Tank" means shit.

 

[Phoenixdriver]

Yeah man....my low fuel light turns on when I still have over 5 gallons in the tank....I have been driving around with the light on for about 3 days now....Just fill up the car, reset the trip odometer, then drive around, when you go to get gas, fill up again, and then divide the miles on your trip odometer by the number gallons on the second fill up .....i just checked my GSX, I'm getting around 22 mpg in the city, with bad tires, and a badly needed tune up...

 

[TeeWX98GST]

I'm just gunna throw this out there.. I don't think I've ever completely filled up my tank Also I have heard rumor you can get more MPG out of a full tank of gas than a partial tank of gas?

 

[Boosted_Curse2]

yes you do. gas evaporates very quickly even in your tank, especially on half a tank or less. The less space you leave for the gas to evaporate, the longer it stays in liquid form like you want it to.

 

[Defiant]

Holy crap, someone call Mythbusters. "Evaporates" how? you have a sealed system, with a vapor recovery system. There's no place for it to "evaporate" to.

Come on, people. Think.

No, you won't get better mileage from a full tank. IF anything, the "extra weight" would cancel out whatever gain you might imagine. And those eighty pounds won't matter, either.