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hi-test vs regular in NA car

Old 02-09-2010, 09:17 PM
Thread Starter
Join Date: Jun 2007
Posts: 59
Default hi-test vs regular in NA car

Started using a little higher octane gas this summer after my mechanic seemed insulted I had been using only regular.. have to admit does give performance a little boost - am wonderig what any downsides might be. I tend to think it has a cleaning affect on fuel/combustion sytem. Any input/comments appreciated.
Old 02-10-2010, 12:05 AM
Join Date: May 2007
Posts: 78

From what I know, unless you advance your timings like with a chip or some kind of adjustable cam, then getting higher Octane gas won't do anything. I'm running the same car as you 86 944 I got a 93 octane chip from http://www.maxhpkit.com/ and did notice some nice improvements, but I mean its not a miracle or anything. Probably not worth the 200 bucks, but it is fun, so your choice. Other than setting your computer up with something designed to run with higher octane your just tossing your money away. Also higher Octane does not necessarily equal higher performance.

Old 02-11-2010, 12:56 PM
Senior Member
Join Date: Jul 2005
Posts: 936

There is no downside at all to using high-octane fuel you obtain from a gasoline station. But on a car that does not specifically require premiu octance fuel (it will be listed in the owners manual and in the fuel filler door, etc., you might be throwing a little money away because regular runs just fine. But you don't know unless you try. It pays to at least try it and see, as was your case. In general, in any older performance car, I would use only premium. Carbon build up over the years can raise compression ratio slightly, requiring more octane, timing may be set a little advanced, you don't know, and older cars do not have the smart electronics that limit damage if octance is too low.

Using very high octance racing fuels might causes problems because they do not have additives street engines need for durability.

The cleaning effect is real. But cleaners are also in lower octane fuels, too. And it is not really a "cleaner" that will make a lot of progress if you have injectors and other problems that are already deteriorated - think of it as additives that prevent things from getting dirtier.
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