Does anyone use any additives? Anyone have any opnions on them? Any of them worthwhile?

 

Do not use oil additives of any kind. The use of quality oil negates the necessity for them. The use of oil additives is usually only needed for very old engines that are having compression or oil consumption issues.

Fuel additives can be used periodically for fuel system maintenance. I highly recommend the use of Chevron Techron Fuel Injector Cleaner. Once every 10K miles is sufficient.