[DML] Re: Premium Gasoline

[Ann & Ed Thompson <RappaRivaRat@xxxx>]

> Ed Thompson said to use the "best grade of premium gas you can find (at
> least 93 octane)". The highest octane level available in many, many places
> is less than 93. Here in the mountains of Colorado, 91 is tops. FWIW.

Yes Dick, this I did say. But I also said "best grade you can FIND". I guess
I wasn't thinking about the folks that live in the clouds on purpose where
real gasoline isn't readily available. If Erik does live in or near the high
mountains of Colorado he can go to a good speed shop and get an octane booster.
That's not a problem. Actually that would be even a better test for troubleshooting
the pinging if it is pre-ignition. He could boost the octane up to 95 or even 97
to eliminate the possibility trying a lower octane that might be marginal and not
sufficient to overcome the pre-ignition.

Or he could come here to Virginia and gas up at sea level with 93 octane. I have
a Chevy van that is supposed to run on "regular" gas (at 87 octane) but if I do
I consistently get pre-ignition. If I use mid-grade (89 octane) I get occasional
pre-ignition under heavily acceleration. If I use premium (93 octane at sea level)
it goes away completely. (No, it does not need a tune-up nor is the timing "off".)

I also have a Corvette that has a much more powerful engine and it will run fine
on any grade gasoline because it has a "spark knock listening" device and a circuit
that automatically adjusts fuel and/or spark settings to eliminate knock. Of course
in the process the engine is "de-tuned" and it loses some power. So I only use
premium grade in it too. As far as I know the DeLorean doesn't have any spark
knock detection device (except for the driver's ear). The DeLorean is supposed to
run fine on regular grade fuel but I have always used premium grades in mine.

It occurred to me that if Erik does have a pre-ignition problem it could be that
the engine was tuned for one altitude and was later moved to a significantly
different altitude without properly tuning the engine for the new altitude.

Ed Thompson (#6419 since 1982)