As I review the board archives, I was struck by the number of posts regarding the recommended fuel octane rating for the S80 T6. Though the manual states that this engine runs best on fuel of 91 octane, my dealer assured me that mid-grade would be fine. I see that some T6 owners use the 89-octane fuel in order to save money and report that, despite some performance loss, their vehicles seem to run okay. After pondering the situation, I did some simple math. Please note that the assumptions used are my own and that yours may differ. In my area, 93 octane fuel sells for only $.04/gallon more than midgrade, but AAA says that the Texas average is $.08, so I’ll use that number. For the first 22,000 miles of its life, my 2001 T-6 has averaged 22.6 mpg. I buy new and never keep a vehicle longer than the powertrain warranty, so I’ll keep this little jewel a little over 4 years, or 50,000 miles. Do the math, and you’ll see that the total cost for using fuel on which the engine was designed to run most efficiently is $177. Please note that I am assuming identical mileage on each grade, even though on a 4-tank test I observed that 93-octane fuel delivered slightly better economy (0.2 mpg) and noticeable better performance than did the mid-grade. Since I paid around $4k extra to get the twin-turbo model instead of the 2.9 engine, $177 seems like a pittance to pay to enjoy optimal performance.
jack <><

My owner's manual calls for a minimum octane of AKI 87 (RON 91). The octane listed on the pump is AKI, not RON. The RON is typically AKI+5.

I understand that fully. The operative word here is MINIMUM. The T6 will RUN on 87 octane, but, as the manual states, it is designed for optimum performance using AKI 91 octane. I am an ASE-certified mechanic with over 30 years of experience in performance-tuning auto and motorcycle engines, and I know the importance of using fuel for which a given engine is tuned. Just as it is a complete waste of money to burn premium in an engine designed for 87 octane, it seems foolish to try to save a bit of cash and burn 87 octane in a T6 designed to run best on premium. As I stated in my original post, I spent $4k more to buy the T6 because of its improved performance over the 2.9. Why in the world would I want to hobble that performance by saving a mere $177 over the entire time I own the vehicle?
jack <><

YOu hit it right on the button, my friend. There have been numerous posts here related to the use of"wasting your money premium". The difference in money spent is negligible that I don't understand what all the anti-premium diatribes are for other than ignorance and sticking to "old school" thinking.

Go with what the factory is recommending (min. 91 octane).

Yannis
--
2001 V70 T-5M SR, Classic Red/Graphite Lthr., ipd ME7 ECU Upgrade, K&N Air Filter, Cold Weather, Dolby Surr. Sound, Rear Spoiler, 17" 'Tethys' alloys

Jack, you only live once.....enjoy your T-6 to the fullest. I dont understand people sometimes......they pony up the extra $$ for a turbo model, and then turn around and want to save a few bucks on what grade fuel they use at the expense of performance?????

Steve Ferraro
Hoboken, NJ

I wish our premium came at that price. Ours is .15-.20 > midgrade which is a dime > regular.

I personally would use the 93.