Millers told me 3,000 miles for road use, less for hard thrashing/racing for their CTV Mini Oil.
I'm thinking of send off a sample of oil to Millers to see how it actually is before I change the oil.
Interestingly Millers have very recently updated their CTV Mini Oil with the Nanodrive additive that they won a Queens Award for!
I've also found the oil in Diesels goes black very quickly.