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I recently brought a mini cooper 2008..and have continued to run it on 95 octane gas...i notice it has a black soot residue in the exhaust pipe..am I better to switch to 91 octane? I have had spark plugs and 3 of 4 coils replaced and put thru a fuel injector cleaner..the black soot has decreased. which fuel would be better? 91 or remain on 95? Thanks..

Hi there,
2008 specs are unavailable, but I can see that a 2009 1.6 turbo and non-turbo both list as using 91 octane fuel, however fuel type used is not usually the cause of black soot.
This is usually an indication of incomplete combustion due to too much fuel being injected into the system (faulty sensors) or by an engine misfire (in most cases coils or sparkplugs).
So the fact that you have replaced potentially faulty coils and sparkplugs may have already remedied the problem.
Turbo vehicles usually perform better on the higher octane fuel, so if yours is, then I would not use 91.

hi there.. .thanks for that...my car is not a turbo..just a mini cooper...i have just had coils and plugs done...i might just switch to 91 then and see how it goes..thanks for your feedback