Quote:
Originally posted by snoman
It is not really their problem. People want high performance in a modern SUV and 87 octane does not cut it a lot of the times. Modern engines have 9.5 or higher compression which does not play well with 87 octane especailly on hot days. Even your owners manual will generally say use at least 89 octane (that is what leaded regular was 20 some years ago) YOur ECM on your moter tries to compensate for poor fuel quality by retarding spark but it only works to a point. You have a few choices, one is to listen to is knock and they other is to use plus or premium in it and you might find that it actually cheaper to operate at today prices because the ECM will retard spark less and yeild better fuel mileage. I do not use 87 in any of my fuel injected trucks.
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That's not the point--or I believe that that isn't what the previous poster (Mrwurm) was trying to make; I dunno about your owners manual but my '03 YXL and '04 DXL manual doesn't "generally say use at least 89 octane". In fact, here is what both my owners manual states, verbatim:
"Use regular unleaded gasoline with a posted octane of 87 or higher. If the octane is less than 87, you may get a heavy knocking noise when you drive. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. Otherwise, you might damage your engine. A little pinging noise when you accelerate or drive uphill is considered normal. This does not indicate a problem exists or that a higher-octane fule is necessary. If you are using 87 octane or higher-octane fuel and hear heavy knocking, your engine needs service."
The above is notwithstanding E-85 or CA fuel requirements, and assumes that the motor is completely stock. In any case, maybe 87 octane may not be the most ideal octane gas to use but based on the above, I don't think GM is saying that the need for higher (89+) octane is required or should be used as a fix (permanent or otherwise) for knock/ping issues. IOW--I don't see GM saying anywhere that our GM FS trucks/SUVs should use a minimum 89 octane (except the HO 6-liter engine used in the Escalade, which IIRC requires 91 octane) if you hear any knocking/pinging. Now, your owners manual may indeed state that a minimum 89 octane is required; however, it is fallacy to insinuate that a knocking/pinging noise isn't necessarily the manufacturer's problem, or that such a noise is solely due to the use of lower-than optimum octane fuel. Besides, it is total BS for a manufacturer to suggest the use of higher octane gas as a--if not the--fix for pinging/knocking noises when/if the owners manual clearly states that the minimum octane requirement is 87. If you read the last sentence in the paragraph I quoted above, you'll see that even GM states that if you hear heavy knocking with 87 (or higher, but it does explicitly state 87 octane), your engine needs service.