Now I'm NOT an expert but I feel sure that most lubricant manufacturers today develop their oils for use with 'un-leaded' fuel. I am prepared to be corrected on this though!

I remember talking with someone from Castrol some years ago who said that their Castrol 2 stroke oil (TT I think??) had been developed with 'leaded' fuel and that the ELF oil that I was using had been developed with un-leaded fuels and was probably better.
This was back in my karting days...and you can't get much more higher stressed 2 stroke motors.

Mike.
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I don't mind dying...I just don't want to be there when it happens!