A friend of mine has an Audi S4 that has been modified to RS4 specs. The company that did the engine has found in repeated dyno tests that they get the most power from Shell's premium. Much more apparently than Sunoco's 94. But those results are from Ottawa and who knows if the results would be valid for the same blends sold in other cities under the same branding? It's just interesting anecdotal 'proof'.

__________________
'96 C280 (gone)
'97 C36
'05 C230k