What Fuel
 

I have a Mark 1 411 (1969/70).

I am currently using 99 RON fuel in it.

What fuels do others use??

Does anyone use 97 RON with or with out a fuel additive.

Would be good to get some advice as wouldn't want to damage the engine

Many thanks

What Fuel
 

I have a 407 with a 318 engine, slightly up on the 313 on rebuild with leadfree heads, cleaned up exhaust ports and manifolds. I always use either Shell V=Power or if I cannot get it BP Optima. In Ireland I always carry copious quantities of Castrol additive.
Difficult to tell if it does as advertised more mpg but I seem to average 17.5 mpg.
Had the car 25 years and until it disappeared many years ran it on leaded 5*

Thanks Nick,

My car is standard with nothing done to heads etc..

I feel I should probably add an aditive and keep going on 99 Ron (Gold Plated Petrol)

Late to the party but for what it's worth I've also got a 318 and when I had heads redone used valves, seats and guides appropriate for unleaded so don't use any additives.
I try to use super unleaded whenever I'm filling up but aren't too fussy about which brand.
Was in France recently and a few times had to use what was available (95 )- no obvious ill effects (no pinking etc).

In standard form these are comparatively low compression engines in a low state of tune - they would have been designed to run on regular US fuel which translates to about 92 RON, I’d be more worried about ethanol than octane.

Using super unleaded is the best way currently to avoid too much ethanol. I have not done enough miles in my Bristol to establish consistent mpg, but in two other cars I found I obtained about 5% more mpg with the super unleaded which completely offset the higher cost of purchasing it.

Esso used to be zero ethanol, but sadly now all fuel has some.

Fortunately for me, I have two local gas stations that sell ethanol-free 89 Octane gasoline. My 408 has a 1978 360 installed and runs well on this stuff.

David

You’re not really going to see more power or economy on something with a carb unless you’re advancing the timing to take advantage of the octane.