frosty46
From size 40 and upwards, MVVS engines are 'timed' to operate on straight fuel - but ought to be able to operate fairly well on up to 5% nitro.

When the engine is new, use a 20% oil content and not much less than this when run-in. A castor content is OK - I use 14% synthetic and 4% castor, for example. Others use a lot more castor content and seem happy with it.

No doubt there are other views out there as well.