Loss in gas mileage..

[Imakrazy]

i know this probably gets asked a lot on these boards but i figured id post my specific situation. i have an auto 98 tj that would typically get 260 mpg per tank and out of nowhere all of a sudden it has dropped dramatically to about 200 a tank. Theres no exhaust leaks that i can here i did replace the manifold a year ago so thats still solid. i have a stock intake on it and once i started loosing mpg i replaced the filter but still no fix. it feels like my engine may be loosing power in some way if anyone knows of any typical problems or any suggestions please let me know this is killing my bank account. also i have tire pressure at 32 i believe... could be wrong but i do know they are all synced in pressure right now and im not carrying anything heavier than usual and not idling anymore than normal. thank you in advance!!!

 

[LGR]

What about the air filter?

 

[Imakrazy]

i replaced it even though the old one did not look to dirty.. :/

 

[bds5]

I have just always chalked it up to "its a Wrangler" as I get about 10 MPG So I'll be watching this thread.

 

[Jester32]

What's the temp any cooler than usual

 

[Imakrazy]

it definitly has been getting more cold outside so i will pay attention to the temp when i drive. and yea i accept that its a wrangler thing too but i know that im capable of 260-290 a tank average

 

[Jester32]

Cold weather it will run rich. My Cherokee gets 320 to a tank in summer and lucky to get 150 in the winter but I also run it for 20 min when it's below zero. I'm in Canada and its -28 c right now. Even 15 degrees will change the mileage.

 

[mud4feet]

Is it throwing any codes? (CEL?) I know when the O2 sensors went bad on my little 4banger (03), gas mileage went WAY down and felt a definite loss of power. Might be something to check.

 

[JPNinPA]

First calculate the gas mileage in MPG. Miles driven by gallons pumped. Miles per tank is deceiving.
Here are a few things to consider:

Winter blend gas and % ethanol. What % ethanol makes a big difference and winter blends have more ethanol.
Spark plugs wrong type, large gap or worn
Clean TB and IAC - smooths out idle and keeps idle low
O2 sensors - go bad without CEL and will affect mpg and idle
Thermostat - engine keep cool too long will not go into closed loop quick enough and use more gas.
Exhaust leaks will give O2's wrong readings and cause rich running.

Other odd things running defrost uses AC and uses more gas.
Failing battery will cause the alternator to load the engine
Failing clutch fan will be constantly engaged loading the engine.

 

[Imakrazy]

wow thank you guys so much for actually giving me these tips, i was working today and i was thinking how when i filled it up i thought it took a few less gallons than usual so maybe next time i fill it up if im lucky just the gas gauge will be incorrect...not likely

 

[ljrubitm]

When was the last time you changed your spark plugs?

 

[Imakrazy]

i havent in over 2 and a half years... i just used half a tank and got 89 miles

 

[superj]

welcome to the jeep club!! mine does that regularly. hit my fuelly link and you can see my tracked mileage since november or october, in all kinds of graphs and stuff