Fuel type

[BobE]

For those with tuned SBC engines what petrol grade do you use. I've seen some conflicting advice regarding whether regular unleaded should be used or something like Shell Optimax - or even alternating between the two.

[BobE]

confusionhunter said:

I tune for 95 so its and shove in premium whenever I can. I have a lumpy cam and some trick bits and around 500bhp with some other special bits. I'm not running massive compression (9.5) or aggressive timing (36) so it will run on anything. Its not like its a high compression, turbo charged, knock sensing, 2 bar of boost, engine that will melt on 95!!
If you have a high power 12:1 highly strung motor on the verge of detonation with mega power, then that gets a bit trickier.

So the answer is really dependent on your engine set up. Do you know what it is?

It's an American Speed 6.3L giving around 550bhp measured by the engine builder so less in the car installation. I'm guessing the compression ratio is 9.8/10.0. The timing is 40 at 3000rpm from the documentation that came with the car which also indicates a 92+ octane fuel should be used. I think most normal unleaded fuel is 95 octane and premium fuels are 98. Having had cars in the past where using too low an Octane risks major problems I wanted to check what others use. It seemed to me regular pump fuel wasn't right even if the engine builder indicated you could go even lower. Comments?

[BobE]

Thanks for all the contributions - I thought it was a simple question but I've learnt a lot more about fuel technology. So if AS reckon 92+ in AKI for the UK with RON that means 97 octane. So that is BP Ultimate 97 or Shell V- Power Nitro at 98 octane. That's until their marketing or engineers go a change the names and I have to recheck again.

[BobE]

UltimaCH said:

V8Dom said:

optimax or if desperate 99 octane from tesco

never used unleaded

Because you can still find leaded in Brexitland?

Not since 2013 and up to then only via specialist companies. The way fuel is marketed in the U.K. is that 95RON is called 'unleaded' where ever you buy it - the higher octane fuels have names to try and justify the extra cost....