Posted: Oct 10 2008 at 6:26pm | IP Logged

........Common. First problem: I have an 07 LE w/ a sunroof, every little vibration makes an annoyying vibration that I've narrowed down to a headliner over the passenger side. Any one else experience this?

2nd, depending on where I get fuel, I iget from as high as 26mpg, down to 12 mpg. All 87 Octane, running a Volant cold air filter w/ ram air. Would I be better off swittching back to factory intake?

Posted: Oct 11 2008 at 6:41am | IP Logged

I know the hi-test/regular debate has gone forever.  But...our engine is designed to utilize higher octane.  Use of lower octane will:

1.  Cause timing to retard.

2. Cause more exhaust gas recirculation.  More of this and manifolds can crud up over time.

With a variable valve timing engine, higher octane fuels will allow you to make use of all of this to the max.  Now, whether you see more mileage may have more to do with tire pressure and driving style, outside temps, etc.  But use of higher octane can set you up for more power and the potential for higher mileage.