70:1 is a super safe bet, I run as high as 100:1 on Bel-Ray HR1 without issues. The low-revving water-cooled electrofusion bore engines are a lot more tolerant than the old aircooled engines. Kinda depends on how you ride, more oil if you're going to be flat out trail riding but less for real trials plonking. Even 80:1 will puddle in the bottom of the crank at trials speed.