NorthValley

I use premium here in Chile. The octane range here is 93-95-97. I use 95 in my SQ5.

slotriathl8

In my neck of the woods Premium is 93 octane, and mid-grade is 89. Manual says Premium, but "91 octane." So, theoretically, if my tank is full with 93 Premium, couldn't I re-fill at the halfway point with 89?
More of an academic question, I always use Premium for the reasons already cited.

ELEVENS

Absolutely you can. Although based upon my data logging, it makes a lot of sense to run 93 octane in the really hot weather because even then, the ECU is pulling timing. As much as 8-12 degrees of advance on my RS4 even with 93 Shell. In the cold, there is practically no timing retard. For about a year, I blended Toluene in my RS4 for performance reasons, about 1 gallon in every fillup (at 1/4 tank), and that really helped the timing retard issue in hot weather. Toluene is roughly 114 octane ((R+M)/2). YMMV

Redd

"Let's not forget that the only way to avoid ethanol at most gas stations is to buy the Premium grade."
ROFLMAO.
Seen a lot of "may contain up to 10% corn crap" stickers on gas pumps, but never did see one that said "except for the premium". AFAIK it is always all-or-none.

Audi built an expensive Flexfuel engine and engine management system in the Q5 to ensure that it can run regular. They want you to burn premium because you will feel superior to the other drivers.

Yes, the engine can get more power for longer periods when burning high test. If you have a heavy right foot you may benefit from that all the time. If you have a light foot?

Come on, folks. The same Audi company and dealer that tell you "should" burn premium all the turn, and the same ones that tell you an oil dipstick does not exist for the Q5.

Yoshimura

Here in Canada, Shell V-Power premium gasoline does not contain ethanol.

Shell V-Power® FAQs - Canada

Redd

They got gasoline in Canada?! BETTER gasoline in Canada?!

Damn, we'd better push up the invasion plans. Oh, wait a minute, you weren't supposed to know about that. Just forget I mentioned it.(VBG)

Houstonken

Porsche, for example, acknowledges that any of its modern production cars can be run on regular fuel without the risk of damage.

A spokesman for Porsche North America, Tony Fouladpour, added a caveat. “If you want the car to perform at its maximum capability, the best choice would not be 87,” he said. “But we do not forbid it.”

“There generally isn’t any harm done to the engine by using lower-octane fuel,” said a BMW spokesman, Thomas Plucinsky. “Because our engines do have very good forms of knock sensing and are able to deal with lower-octane fuels, you will not have any drivability issues. You will, however, lose some of the performance.”

How much of a loss? Some indication can be found in the peak horsepower numbers Hyundai recently released for its new Genesis sedan. On premium, the 4.6-liter V-8 engine is rated at 375 horsepower. On 87-octane regular, it is 368.

That seven-horsepower difference — less than 2 percent — seems a small penalty for saving 30 cents a gallon, especially when you can regain that performance simply by filling up with premium.

http://www.nytimes.com/2008/08/03/au.../03OCTANE.html

Redd

"That seven-horsepower difference — less than 2 percent "

So...when I did a 5>3 down shift on the highway, or (ahem) a 4>2 downshift and found out that at WOT there was indeed a redline throttle limiter...at times like that, a modern car like this would have an extra 7hp.

Instead I have to deal with an automatic shuffling around in eight gears now.

Memo, flush and fill with hitest before trying to terrify the local drivers.

Xenonista

The Hyundai Genesis appears normally aspirated, with a compression ratio suitable for 87 octane. I'm surprised it benefits from higher octane at all. These are huge, bleating V8 engines with 4-5 liter displacement. No exactly comparable to a any contemporary Audi angine.

Redd

"These are huge, bleating V8 engines with 4-5 liter displacement"
Oh you kids. A "huge" five liter engine would be the Ford 302, which started as an overbored Ford 289, which was always a TINY V8. In fact, about the smallest size V8's were built in.

In contrast, a 455 or a 464, now that would have been a "huge beast".

A 350ci V8, at some 6 liters, was considered the TYPICAL size for an American V8 engine.

Huge 4-5 liter engines. ROFL!