Unleaded fuel conversion in 131

[cooter131]

Hello all,

I came up with a question that might sound funny, so please be kind with me

I do not know how the situation is in different parts of the world today, but in Greece you can still find Super LRP fuel... (and unleaded, of course )
I think that the Super does not actually contain lead the way we used to know it, but some kind of substitute.

I was wondering if I can use unleaded fuel in my 131?
Some say that it is not a problem and others do not suggest it.

Are any conversions necessary for use of unleaded fuel?

What kind of fuel do you use, and what do you prefer?

Sorry for the numerous questions...

[Thotos]

I'd say you're fine to run with unleaded but as you've already said, most people will disagree with me.

Lead was used in petrol to increase the octane rating but also and mainly to act as a lubricant for the valve seat and stop valve seat recession. But 'modern' classics (if I may use that expression  ) like the Fiat 131 have an aluminium cylinder head and because aluminium is too soft they have hardened valve seat inserts. Some people will tell you that the hardened inserts are not hard enough but even though there's some truth in that it will take many tens of thousands of miles before there's any adverse effect. So why pay to have your valve inserts replaced now if you can drive for 100,000 KM before you have to change them?

The reduced octane rating is your other problem. Your 131 was designed to run on 97 octane fuel or even higher while unleaded fuel has a lower octane rating (95 in the UK). Using lower octane fuel in your 131 may cause pre-detonation or 'pinking' and if you get that then you should reduce your ignition timing. Normally a 131 should be set to 10 degrees BTDC so try reducing it to 8 or 7 degrees but avoid going below 5 degrees as performance will be reduced a lot. You can also use 'Super unleaded' fuel which has a higher octane rating or use an 'octane booster' additive every time you fill up. Shell in the UK now have 99 octane Super Unleaded fuel and the 131 really likes that fuel!