Thread: Just a thought

This question has been rolling around in my mind for some time. If a good seal from piston to cylinder is needed for proper running, wouldn't these friction modified oils try to reduce this seal and affect performance. I am under the impression that the rings run on a very thin layer of oil. If this is more "slippery" wouldn't cause a problem? Jim

Piston ring seal is achieved by ignition/combustion pressure travelling down and around the top of the piston and getting behind the step in the top piston ring and forcing the ring onto the cylinder bore face.
This is why bores glaze up when the engine is subjected to too long at idle speed, not enough pressure.
The bottom oil control rings keep as much oil as possible off the bore surface so as the compression rings can do their job.
It is advisable when running a new engine that you should use basic Mineral oil and not super slippery Synthetic oils, once the engine is run in (Piston rings formed and sealing on the cylinder bores) you can return to Manufacturers spec oil.
My Perkins 6354T has a warning from Perkins to NEVER use Synthetic oils in this engine.
If you have poor oil control rings, Synthetic oil would be more detrimental to ring sealing than Mineral oil.
I would recommend you consult the engine builder (LR in this case) on what is the recommended oil to use, then follow that advice, Regards Frank.

Originally Posted by jx2mad

This question has been rolling around in my mind for some time. If a good seal from piston to cylinder is needed for proper running, wouldn't these friction modified oils try to reduce this seal and affect performance. I am under the impression that the rings run on a very thin layer of oil. If this is more "slippery" wouldn't cause a problem? Jim