I am currently restoring a Series C Rapide which has been off the road for several years. Is there any general consensus about what is the best type of modern engine oil to use, e.g. single grade or multigrade, detergent or non-detergent, etc.? The bike has new low-expansion pistons and Alpha big end. I have a modern bike for winter/general purpose use, so the Rapide will mostly be used for longish runs April-October.