Since new I have used 91 octane premium fuel (PetroCanada mostly) in my 2005 MCS with JCW engine tuning kit – However, since 2010, I have been using PetroCanada Ultra94 Octane fuel – because it became available nearby and seemed to be the preferred octane recommended for the JCW engine (Refer JCW Certificate of Authenticity: “Always use 98 ROZ/RON fuel or the highest octane fuel available (95 ROZ/RON/ Gasoline 91 AKI minimum)”

Essentially this statement on the C of A translates to: 91 octane (95 ROZ/RON) is minimum acceptable but 94 octane (98 ROZ/RON) is preferable. 94 octane is not readily available in many parts of Canada – so originally 91octane seemed the only reasonable choice.

However, I recently reviewed some supplier specs for premium fuels – specifically Shell V Power vs. PC Ultra 94 Premium. Seems Shell V power 91 Octane has no ethanol while PC 94 Octane has from 5-10% ethanol. Fuel mileage is not really an issue as there has been no significant mileage difference between PC Superclean91 octane and Ultra 94 octane.

I am not a fuel expert so would like an expert opinion as to which would be a better choice for this engine (in terms of performance, longevity and reliability) (10 yrs old MCS but very low mileage)

91 octane without ethanol?
94 octane with up to 10% ethanol?

 

Ethanol is evil incarnate. Stick with a known that meets the standard and avoid the unknown that MAY cause long term injury to auxiliary fuel system components.
Not an expert opinion by any means but an old guy who doesn't trust gov't mandated 'green' ideas that turns FOOD into FUEL and consumes more energy than it can deliver and is know to do an Andromeda Strain number on rubber type components..

 

I'd go with the gasoline without ethanol. It's negative effects on fuel systems are well documented, especially for older fuel systems. I truly wish I could buy ethanol free gasoline for my '03 and '75.

 

+1

 

Ethanol free for sure would be my choice.. No 91 available here,87,89 and93.I will be using 93 top tier (mobil) . Wish i could find ethanol free.If i mix 89 and 93 i can run 91..which is the suggested octane for F56 turbo motor..

 

Don't fuss with mixing octanes. We've only 91 octane in our area but when we travel and 93 is available our mileage and driving range go up considerably. The li'l guy fairly kicks up his heels in joy. So, the perceived economy of mixing might be an illusion.

 

no mixing here,just an observation.I run 93 in my 2006 saab 2.0 turbo and see a mileage and performance advantage.that car has variable timing which adjusts for octane used.

 

Ethanol is not a problem for today's fuel systems. It's great for the engine though. It burns much cooler than gasoline. Being only 10% might not have such a beneficial affect as E85 does.

 

Thanks all for the feedback. Definite strong sentiments against ethanol - requires some additional consideration - possible switch to Vpower - not quite sure yet.
Thanks again.

 

Chevron Canada also sells 94 octane (no alcohol) and the only fuel I put in my MCS. Pure octane fouls less than ethanol blend being less hygroscopic.