[Shotimes] Octane requirements and old engines

[Ron Porter]

The only really good SHO example I had that I call valid is the '89 that I
owned since new. Helps when you know the maintenance history, and how it was
driven, but it did fine on 87 for the 82K that I had it, even after doing
the BOS with the LPM at around 135K. Can be hard to tell with a used SHO,
since you don't know it's life history.

Yep, oil has a pretty low octane rating!

Of course, with 280K miles, "normal" (compared to under maybe 150K-mile
engines) really doesn't apply!!

Ron Porter

-----Original Message-----
From: shotimes-admin@autox.team.net [mailto:shotimes-admin@autox.team.net]
On Behalf Of Leigh Smith
Sent: Saturday, April 09, 2005 12:55 PM
To: SHOTIMES
Subject: [Shotimes] Octane requirements and old engines

I agree that normal winter regular fuel seems to work well in my SHO's too.
The reformulated summer version gas seems more in-consistent (NJ) regarding
pinging.
Two other common pinging issues regarde engine condition: both carbon
build-up
and oil consumption (past rings/valve guides) raise the octane requirement
of
an older engine considerably.
There are top engine cleaners out there that work very well at
de-carbonizing
the piston tops. (The GM one is fabulous).  I used it at six month intervals
on my '89 SHO once it went past 150k and it made a slight difference in less
pinging. The SHO has less carbon build-up and/or is less susceptible to this
sort of pinging than other cars I have had & seen.
However, once the engine starts to burn oil, it pings more, so you just have
to use better gas to stop the pinging. Once it burns enough oil that it
pings
on 87, try 91, etc. Once it pings a lot on 93, then it's engine rebuild
time.
Never reached that point on my 280k mile'89 SHO, however it didn't like 87
octane any more, it pinged too much, so it was starting to go, so I ran 91
or
93.  (Ahh gee...only 280k too)
I had an older 4cyl that died at 189k, the rings just quit within 20-30k
miles. It pinged so bad at that point, even on 93 octane with octane
booster,
it sounded like pebbles in a coffee can; non-stop. That engine was rebuilt
and
it needed nothing except a new set of rings, which were shot. The plug tips
were very heavily oil-coated, so it was just the oil making it ping.
Our SHO's are definately built better than that. IIRC I heard the rings were
chrome. That type of ring last a long time, as we have seen.
Lee
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