hcbph said:
Question - why are you putting premium in your Vette? If you have the L98 as you said, it's unmodified then it should have 9.5-1 compression ratio. That should run on 87 octane regular just fine. You're not getting any benefit by running premium
I had this conversation with an Instructor at the GM training center in Burbank, back in 1985 shortly after I purchased my 85 new. Here was his reply:
"Sure, running regular won't hurt the engine, because the timing will be retarded if detonation occurs. But if the guy running next to you has premium in his tank, he may beat you because his engine will be producing more power, because his timing ISN'T as retarded as yours."
I've never forgotten that. And of course he's correct. Running premium
may not be necessary to prevent detonation, but it certainly may be to derive the maximum
potential performance.
Another thing to keep in mind is that "premium" back in the 80's was typically 94-97 RON, and "regular" was 91-94 RON. Today "premium is 91, and regular is 87. Not to mention ethanol's "contribution". Todays "premium" isn't as good as "regular" was when the cars were new. Or, the gas today doesn't meet the specs of the gas the engine and tune were engineered to run on.
I haven't logged my 85 for performance for decades. (My Diacom laptop expired at least 10 years ago). But it would be an interesting study to log the differences in timing-retard between the two octanes in back-to-back comparisons where other conditions like ambient temps and the test-course could be somewhat controlled. My guess is that one could see the additional retard when using the lower octane.
The "benefit" one may receive by running higher octane in a vintage C4 is the better performance, drivability, and fuel economy that running with more timing advance than can be achieved with lower octane gives.
My .02
|UPDATED|7/10/2014 2:37:41 PM (AZT)|/UPDATED|