In a message dated 29/04/02 7:50:33 AM Pacific Daylight Time,
owner-mgs-digest@autox.team.net writes:
> I use premium in all my cars, even my TD. Even though the TD doesn't need
> it, I figure the extra octane is a hedge against pre-ignition in the event
> the engine overheats or the timing gets out of whack. Does this make sense,
> or am I being stupid?
>
Stupid is putting it much too strongly.
Your mistake is commonly made by the public at large, who think that higher
octane must be better and will give them more power, more hair, less midriff
bulge.......when really, you want to run the LOWEST octane you can without
ping. Don't worry, the guys at the race track make the same mistake, and run
higher than they need, when lower would actually give them more power.
I have seen MG owners countless times saying that their car pings on regular,
and has to run premium, when all they are really saying is my engine is a
carbonned up piece of ______ that won't run without pinging unless I use a
higher grade of gas than I should need. The problem is exacerbated in MGs by
the sloppy casting work at the factory with sharp wedges galore, and the
'Weslake point' often needlessly acute, especially on earlier versions of the
B series engine.
If you tear the engine down, a half hour of grinding and sanding will do
wonders to prevent future carbon build-up and you should be able to run
regular with the low compression cars, and mid grade with anything but a
Twincam, which requires premium.
I use 92 on my Jensens (10:1), 94 on my street Fiero (8.5, but 13 psi boost)
and Lamborghini (10.7), as well as TVR race car (HRG head, 10.5), and only
need to go to 105 for the Twincam (12:1)
My street driven (when it _gets_ driven) 62 MGA Coupe gets 89 and loves it.
Bill
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