BP Ultimate and Shell Optimax

[uumode]

Only buy Optimax from a busy garage though as it has a shelf life which is measured in weeks due to the very complex and volatile additives.

Mark

Hmm that's interesting, and maybe that explains the variances in the batches of Ultimate (if it's the same sort of composition) that I've used.

Or maybe they have a 'summer' and 'winter' mix too, the overlap producing mixed results.