Quick update. Went to Dallas this weekend. Got 22.7 MPG going to Dallas and 22.1 coming home. Calculated MPG myself, it matched computer calculations each time.
Car is at dealer today.

 

Got car back last night. They updated the computer.
On the way hame, I reset the onboard computer and drove the expressway for 10 miles. Computer showed 28 MPG Avg. The best I've ever gotten. I know this is not the ultimate test but it does look like the mileage is better than before.
Now if they would just fix the rear wheell alignment.

 

Higher octane no matter what the compression is = better burn more complete scavanging of cylinders and more btu equalling more power. Its rated in octane for a reason if you can afford for the difference in performance do it. most people go the other way with it, because of cost but it will definately not hurt your mileage, just think If you can produce a better burn you get more thermal units creating more power. More power = less effort to push the mass. If it were a compression situation as suggested you would have to use higher octane to keep from predetonation. you should be getting more MPG. I have an 06 and get 26-30 depending on speed avg. start looking it could be small air filter, tires etc. but if you can afford the good stuff your doing good it will help your engine in the long run too. And if all that tech stuff doesnt make your mind up prove it, put different grades in and see I think youll see the difference.

 

Jester,

Do you have any information from a reputable source to back up this claim? Im very interested to see... If using a higher octane gas really increases your gas mileage, then why would lower octanes exists? We are talking total out of pocket cost here right? So when you break down miles of travel per every cent spent on gas, it would ALWAYS be cheaper to use higher octane gas as you state.... Not talking $ per gallon, talking $ per mile..... Just doesnt make sense.

 

For reference, read this:
http://www.ftc.gov/bcp/edu/pubs/cons...ts/alt064.shtm


or this:
http://dnr.louisiana.gov/sec/EXECDIV.../trans/b/b.htm

or this:
http://www.state.mn.us/mn/externalDo...ctaneFacts.pdf


ok?