rcy

Ok..my manual says to use 87AKI or 91RON. Does this mean I can use regular unleaded or do I need high octane? I have an '88 with 200000km on it. I was at an Esso station (like Exxon in the states I think) and the pump had sticker that said (R+M)/2. I think this is the RON number which means I need to use high octane
Thanks

Charles Bisel

Christ, it took over 5 minutes just for this damn post to load up!

Anyway, the entire equation [ (R+M)/2 ] is the AKI number. For our vehicles, that is 87. That's what 'octane' you use.

The R in the equation is the RON number. For our vehicles, that is 91. The M in the equation is the MON number. Even though it isn't listed in the manual, for our cars it is 83.

My guess is that some countries outside of North America may use the RON number to determine their 'octane rating'. Technically speaking, the RON, MON, and AKI are all ratings of octane, but it is the AKI that we go by in the U.S. and Canada.

So 87 octane is what you want to use in your car unless it knocks or pings on 87, in which case you'll want to use 89 or 91. It shouldn't knock or ping unless you have a lot of carbon built up in your engine. If you run too high of an octane in your car, chances are you will build up carbon, so go with the lowest you can.

I've run 87 for 3 years now and the car runs perfectly fine and the timing is set to factory specs. If you advance your timing, then you'll have to use a higher octane.

-C-