What Fuel

[Martin9645]

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

[Nick Challacombe]

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*

[Martin9645]

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)

[AndrewA]

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).

[Philip]

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.

[Xseries]

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.

[dwomby]

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

[Philip]

Originally Posted by Xseries

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.

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.