Premium Gasoline

Exactly. Back in the late l970's, the eastern U.S. mostly had two types of gas - leaded "regular" at 89 (that is [R+M]/2) octane and leaded or unleaded

95 octane premium. Amoco was one of the first companies to drop the octane of their premium from 95 to 93, and the Maryland state comptroller decreed that they could no longer market it as "premium" in the state!

I don't understand how 89 has now become premium rather than "mid-grade", unless were talking about high altitude areas of the west.

Tom K.

Reply to
Tom K.
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It's always struck me as strange that the lowest octane in the UK (95) is described as Premium - especially as under the old star system it would have been Regular...

Reply to
Dave Plowman (News)

The OP does not give an actual single recommended number (89 or 92) but it would surprise me if the manual did not state a figure.

DAS

For direct contact replace nospam with schmetterling

Reply to
Dori A Schmetterling

Quite so. Am glad to note that I am not the only one scratching the head over that one...Probably the price today (in non-infllated-adjusted terms) is at a premium over the one in force when a putative 95 (since in the old days there was no 95 IIRC) cost less...

Similar/greater confusion exists in other countries, especially where

91-octane (European/international) is still available.

Devalues the language. What is premium when there is a super? Super petrol at a premium price? Or peremium petrol at a super price?

What about the hotels whose basic room in the broom cupboard by the clanking lifts is called "superior" and the next one up is "executive".

Superior to what? A bed in a toilet? The youth hostel next door?.

You can just see it, can't you? No more "good, better, best". Just "superior, executive, junior suite".

DAS

For direct contact replace nospam with schmetterling

Reply to
Dori A Schmetterling

Agreed, the savings are small. But isn't it true that most recent BMWs can automatically adjust certain aspects of engine operation to match lower octane gas? In other words you may sacrifice a little performance but no harm will be done.

Reply to
Peter A

Yes, that is true of almost all cars today. If the engine has a knock sensor, it can sense detonation and retard timing and make other small changes until the engine can live on the fuel you feed it. In most cases you will lose power and also fuel economy. If you lose more than 8% in fuel economy, it's a wash and you'd be just as well off buying premium for $.20 more per gallon. In my case, my Z3 1.9L gets 26 mpg on premium 93 octane. If I drop to 91 octane and get 25 mpg, or 87 octane and get 24 mpg, it will be the same fuel cost per mile. Smiles per mile will also drop.

Reply to
Rex B

If it's retarding the ignition because of lower than ideal octane it will also give poorer MPG as well as performance. The trick is working out the actual running costs.

Reply to
Dave Plowman (News)

"Fred W" wrote

Fred, do you live in CA? My '91 525i M50 says 90AKI/95RON in the manual. I don't believe that the VANOS M50TU was any different.

FloydR

Reply to
Floyd Rogers

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