Mr (The) Bob Farnham recommends using nothing else but Shell Optimax for all but the most severe of his tunes.

I use Optimax in 2 highly tuned engines and have had no issues at all.
If you mix Optimax with avgas 50:50 you get a slightly better fuel suitable for track bikes - more stability in the burn and will tollerate higher compression ratios.

If you can afford it - use 4 star leaded.


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These aren't the droids you're looking for.