Bad gas mileage question

06GreenMachine

New member
Hey everyone, 

        I have a 2006 Impreza wagon and I recently noticed that my gas mileage was very bad, doing 50 ish miles on 1/4 tank. I just changed the air filter and that is when it started. I read on NASIOC that it might need injectors. are there any other things I could be forgetting?? 

Thanks Josh

 
Internet diagnosing is a pain. Two things could be going on:

Your sending unit for fuel level is bad (calculate your mpg)

You do have a problem, but who really knows what it is. If you are dumping too much fuel in the engine then it will show on the spark plugs, they will be wet or black after running the car.

Here is what I would do myself. Clean your mass airflow sensor(with MAF specific cleaner), check the vacuum lines on your intake, PCV valve(make sure it still moves), fuel filter, and spark plugs(basic NGK, those "better" multi electrode ones are junk for our engine).

 

injulen

New member
+1 on calculating your gas mileage manually. My fuel gauge gets to half a tank and then drops to below E sometimes. Worn out parts suck. But I just keep the trip meter reset every time I fill up and then I know how much gas is in there based on how many miles I have gone.

 

SUBARUDE

Well-known member
Also how many miles are on your car and does it have any running issue or check engine lights on?

 

06GreenMachine

New member
I cleaned the mass air flow sensor the with crc mass air flow cleaner and it seams it be better, i will keep an eye on it for future issues. If it happens again ill pull the plugs and go from there. Thanks for the help eveyone.

 

i-wagon

Well-known member
I'm late to this thread, but I have a bit of input. My 07 hated k&n filters. Not sure what your air filter is, but oiled one's get oil on the maf, and it had to be cleaned, like you already did. Up stream oxygen sensor made it chug fuel as well. Plus modified headers took away almost 5mpg with an axle back. I only got 23mpg towards the end of ownership, mostly caused by the uel header and my driving. Honestly,I think that's not bad for what the car was. Maybe run some cleaner in the fuel, I used sea foam twice a year, May work may not. Also, long shot, rev it a bit with someone watching the tailpipe and see if it smokes black (rich) I'd done something at one point that made it rich, can't remember what though

 

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