Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 95 or 98 octane gasoline?

Hello everyone!

Which octane gasoline do you use / recommend for the M3W? 95 or 98?

Have you noticed any real difference running one or another?

I'll finally pick up my M3W next Thursday and, as usual, first thing to do is filling with gas, as the dealers (at least here in Spain) deliver the cars with a ridiculous volume of gas, barely enought to get to the closest pertrol station….

Thanks!

I’ve always used 95, never had any problems with it ....

In Switzerland we use 100 octane - it’s brilliant - 98 or 99 in the U.K. if you can get it.

95 is ok but you certainly will notice the difference with higher octane. More bang for your buck!

If you have the standard restrictive exhaust fitted you will probably get pinking on anything much over 4500 rpm, I would say that the higher octane the better to help try and reduce this. The best cure all round is to fit a less restrictive exhaust system. The engine runs better and cooler with no pinking.

over here the only 95 octane you will find is at altitude. So I imagine it is measured differently. 98 is premium over here which is what the V-twin needs

Just checked the engine workshop manual and it says “it should be minimum 91 - don’t use fuel additives and avoid methanol based fuels. Ethanol blends up the 20% are acceptable”. Try 95 and 98 - if you notice a difference and its worth the expense you have the answer. I’ve always used 95 for the last 40,000 miles and I tend to avoid E10 where I can. Just enjoy!

My manual says 95 or 98. After your comments I'll start running on 98. The Price difference for the milleage I'll do to the car is peanuts… and aI agree it might run smoother.

I always use 98, never tried 95. 98 that’s a few weeks old maybe is probably nearer 95 anyway.

There is a problem when comparing Octane numbers in Europe with the USA, as they are slightly different, Google says. Europe uses RON (Research Octane Number) and the USA uses MON (Motor Octane Number) or PON (Pump Octane Number). It means that 93PON is equivalent to 98RON. The S&S info that says to use minimum of 91 Octane means 91PON in the USA (probably?) and that equates to 95RON in Europe, which seems sensible. I use 98RON whenever I can but use 95 otherwise, no problems with either.

That is absolutely correct the S&S manual is referring to the US rating i.e. 91 PON which is the common highest fuel rating over here. My M3W runs perfectly well on the US 91 PON, interestingly a few UK Mogs on MOAVII had hesitant running because they were using US 85 instead of putting 91 in the tank.