Well it depends on your needs. We race the Capri V6 on a mix of premium unleaded (95 ron) and Millers CVL additive. This is designed to stop valve recession under extreme conditions like racing. It is also an octane booster so there was no need to retard the ignition.
I run my MGB on unleaded and Millers VSP additive. Again there has been no need to retard the ignition. Also performance has improved to the levels that the original four star leaded gave.
I have never used lead replacement fuel and indeed there is a story that it will be phased out at the end of this year because of a lack of sales. Personally I wouldn’t recommend it.
