Im getting around 130 miles per tank at 93 octane ! Possible causes of bad mpg? Already changed sparks plug, cleaned maf sensor, next step is to change o2 sensor..

 

You should check your fuel trims. Do you have a check engine light? No reason to replace your o2 if its working. Diagnose is it, don't just start replacing parts. Is the fuel consistent where you live, do they add ethenal to it in different parts of the year?

 

Yes i have the check engine on. I think is its better to get a scanner.. And no the fuel in my area is consistent all year

 

Ya the first think to do is find out what cel code you have. Instead of buying a obd2 scanner go to the evo scan website and buy the right cable (probably 1.3u) and evoscan software. That way you can learn how to log your car and really find out exactly what's happening. Good luck with it man.

 

Damn i thought mine was bad and im on 91..
have you kept with maintenance?

 

Thanks. I appreciate your help

 

Yes my evo is working great everything seems to be fine except for the bad mpg and check engine light on

 

most autopart stores have code scanners they will read the codes for free.

 

Stock injectors and fuel pump ? I get around 140-150 miles per tank city in my car but I have 1250cc injectors and bigger fuel pump so I just assume that's it but I get great highway Milage

 

Things I would do:

Run some fuel system cleaner
Reset your fuel trims (either through ECUflash or by pulling your battery for 10-15 mins)

Check for boost leaks
Check your injector seals
Check your tires/alignment

Good luck.
I had a similar issue and it was one of my injector seals not holding at 31 psi. it sprayed gas everywhere.

 

The basics come into play here as well, lead foot. Ease up on the gas and stay out of boost.

 

What type of fuel system cleaner you recommend ? And if cars tuned will unplugging battery for 15mins still reset fuel trims ?

 

could be many things
but most likely, Bad 02 sensor or injectors, Check for a fuel leak somewhere.. but could be vacuum leak or just really dirty air filter.