Subaru Impreza GC8 & RS Forum & Community banner

1 - 4 of 4 Posts

·
Registered
2004 Forester XTi
Joined
·
1,005 Posts
Discussion Starter #1
My car gets a tad jumpy when at idle when it's warming up, and the engine is a little loud. Well, I thought nothing of it and replaced my tank with 89 octane. After I parked the car for 2-3hrs, the engine got cold again here in Minnesota. I warmed up the car and drove home. The butt dyno didn't feel the jitter the 87 octane. I'd have to say the engine runs like it was new again... really smooth. I just don't know if performance can be affected with the change. Does anyone have/worked with this problem?
 

·
Premium Member
2001 Subaru Impreza RS
Joined
·
586 Posts
I saw a consumer reports thing floating around or something like that that said higher octane won't really make a difference in our measly 4 bangers. I know this isn't true especially here at altitude, my car starts dragging major ass on regular unleaded going up the mountains. Tons better with higher octane.:confused:

Nick C.
 

·
Registered
2004 Forester XTi
Joined
·
1,005 Posts
Discussion Starter #3
Since some of us do modify the areas of our cars to improve performance, is it that since an intake system gets in more air and an exhaust system allows better flow of unneeded air we'll need a little better combustion process within the engine? (long sentence, huh?:happynow:) Therefore, I'm sure using higher octane will allow better/easier combustion for the added air. Am I right?
 

·
Registered
Joined
·
116 Posts
I don't put anything less than 91 octane in mine (one tank of 87 and the she ran like a dying dog until it was gone!) The higher the octane the better the engine will perform over wide variations in driving conditions. Relatively speaking our compression ration yearns for the HI TEST! And when I add an Octane Booster to push it up 10 base points it performs even better....runs smother, accelerates faster and gets better gas milage (when I keep my foot out of 'race mode'!) Lower octane fuels tend to predetonate...the knock sensor catches this and retards the timing......less power and poor overall performance is the ultimate result! I tested the difference between 91 and 92 last summer on two identical trips, same load, same temp, same speed (70mph ave)... 3 mpg improvement (20 to 23)! :sunny:
 
1 - 4 of 4 Posts
Top