The last few tanks of my gas had dropped about 5mpg. I havnet driven anymore in the city w/ these tanks either. My question is: What could be causing this? Some have told me that since I run a 160 stat, that it causes you to get worst mpg? I could always switch to the 180 instead!

Any ideas?

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91 RS Camaro
3.1L
Cat Back System, K&N filter,modified air box, Fastchip Stage 2, 160 thermo, Rapidfires and Bosch Wires 5 Air Horns

Kills: 89' 302 Thunderbird, 88' 305 Cutless Supreme, 90' 3.8 Bonneville

My Car

 

Swap your t-stat if you have any doubts about its condition and try a 180. But if you notice that your mileage is still basically the same, then it is most likely your gas.

Many of the oil companies "winterize" their gas and I have always noticed that my mileage drops during winter...longer warm up being a part of the reason. Also, due to the cooler air, fuel injected engines will add more fuel to maintain 14.7:1. Cooler air is denser air.

But on top of that, the additives they put in just makes my car consume more fuel. I ALWAYS get better mileage during the summer when they go to a summer blend.

I am assuming that you have recently tuned your car and are still noticing this.

 

Glenn,

Its like it happen all of a sudden (over 2 gas tanks). I am thinking it is a combination of 160 stat and the bad gas in the winter.

Does anyone else have any other opinions?

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91 RS Camaro
3.1L
Cat Back System, K&N filter,modified air box, Fastchip Stage 2, 160 thermo, Rapidfires and Bosch Wires 5 Air Horns

Kills: 89' 302 Thunderbird, 88' 305 Cutless Supreme, 90' 3.8 Bonneville

My Car

 

cold air is denser and holds more gas molecules so it squeezes more gas into it...thats also why u get better performance when its cold, and why everyone makes cold air intakes

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Flowmaster 80 series, Random Technologies Cat, 3" intermediate pipe, SS
Hand Made Tips, 3 1/4" out, Accel 8.8 wires, MSD Coil, MSD Ignition Module,MSD 6A Box
Currently Working On:
T5 swap
Next to buy:
Slp dual cold air intake!

1982 z28..
350 4bbl black leather inside and black outside...no mods yet except for maybe the exhaust from my firebird

 

Might also be time to do a general tune up.

 

I'm with Glenn,
but don't forget the O2 sensor.

 

Glenn and Graemes are both right. The winterization process oil companies put gas through (I've been told anyway) causes gas mileage to decrease...don't ask me why.

However, a more noticeable decrease is due to the fact that it's friggen cold!! My MPG the last 2-3 weeks has dropped about 3-4MPG....normally I get 22-23 combined, and now I'm in the 18.5-19 bracket.

But the car is pulling harder when I get on it...so it's all good

 

****..usually i only get 10 miles a gallon..flooring from each stop sucks !

------------------
Flowmaster 80 series, Random Technologies Cat, 3" intermediate pipe, SS
Hand Made Tips, 3 1/4" out, Accel 8.8 wires, MSD Coil, MSD Ignition Module,MSD 6A Box
Currently Working On:
T5 swap
Next to buy:
Slp dual cold air intake!