Morris Minor Owners Club

I am soon to commision the sidevalve engine in my Series MM.

I was wondering about what Octane fuel was best?

Seeing that when the engines where originally made
all you could get was a low octane fuel, I was wondering
is the standard unleaded 92 Octane was OK,
or I have been told that with older overhead valve engines
that a 96 or 98 Octane is better.

Also I assume there is a need to use a lead additive as well?

What do the masses advise?

I found that with higher octain petrol I had fewer burnt out valves. Since I now have an unleaded engine with hardened valves, seats and guides that is no longer a problem and I use ordinary unleaded 95 Octain. With the compression ratio of a side valve there is no point in using anything higher

Hello again Mike,

My engine has not had the head modified with hardened seats,
so would you recommend the lead additive for my engine?

Thanks Oli

If you are doing high speed, high mileage runs then it probably is worth using additives but if you are just pootling around locally then I would not bother