At the LHS....

For the oil I use with great succes 3% Castrol Racing-M (formally known as M50) and 6% Castrol MSSR. Currently we are experimenting with Shell Racing-M which seems to work good as two 10th scale drivers were using it in the past season and one made it to national champion. The only problem with the Shell oil is that it has a very dirty combustion but with engines living up to 12 liter on maximum performance and still having a lot of pinch that is no problem.
The Shell oil is very thin (SAE30 specs) which must help reaching high revs.