Hi I recently purchased a 2006 STi. It has 52k miles and is stage 2 protuned with a invidia catless downpipe and hks carbon ti exhaust. Car is making 275whp/300wtq on a mustang dyno when tuned at GST 2 years ago.

I have driven the car about 2k miles and used to get 14mpg all city in the summer, now when we are approaching winter i am getting 11-12mpg city. I rarely drive freeway and this low mpg has gotten me really worried. I drive without boost and rarely ever boost the car hard. Ive read people with stage 2 sti's averaging 16-20mpg city easily but im not sure why i get only 14 and now 11-12. I really hope there isnt something wrong with the car but i can't come to find out why its getting such low mpg. I recently changed my oil, cleaned my k&n air filter, and removed my BOV (came w/ car) and put BPV back on. I drive really conservatively but this 11-12mpg is killing me. I used to get about 180-190 miles a tank but now its dropped to 150ish.

What am i supposed to do to fix this? I would drive it to GST to check since i read that theyre a good shop but i don't know what needs to be done. My tires have been at 36psi/all (cold) to 40fr/38rr and the mpg hasn't changed. I tried everything i could think of. The car gets shell 91 gas and oil before was under 2k miles according to previous owner.

Can you guys please help?

Thanks a lot!

 

Have GST look at it and diagnose it. You can have a bad tune or need engine work.

 

+1.

 

The k&n air filter is oiled....check the maf sensor,might be dirty.

 

Dirty Maf would cause lean condition no?

I tend to run a little richer when its cold so that may be it but your mielage is deffinately way off.

I would say bring it in to GST as well especially if they originally tuned it. It may just be time for an overall tune up.

 

I've recently sprayed the maf with a cleaner but it didn't change much. What would be included in an overall tune up? Just spark plugs right? And how much would gst charge for a checkup I'm really tight on money right now thats why I'm hesitant to take it there

 

I would just call. Mike and crew are great guys. They can tell you what all is included, and what it would cost.

to save you the time of looking it up. 510-264-9049

 

Thanks Shay i would really take it in but school (get out kinda late) and my budget have made me a bit lazy

 

I would get a compression test done before doing any major service.

 

but.... 14mpg to begin with is pretty low... maybe they switched to winter gas already?

 

Maybe I'm new here but what is "winter gas" ?

 

Different blend of ingredients used by the refineries, usually results in slightly lower fuel mileage. Helps with cold starts and extreme (not so much in CA) weather conditions. Winter blend usually starts appearing around the middle of fall, and summer blend usually takes over sometime in spring. From what I have read in local newspapers mostly.