Dave wrote on 04/23/20 at 18:37:58:Youzguys ran the first 60,000 miles using Valvoline VR1 in 10-40 I believe, the next 100,000 miles was using Rotella T6 in 5W-40. At the 160,000 miles rebuild the only thing that was out of spec was the valve guides and valves. The cam and rockers were fine, the piston was fine, and even the rings were still in spec.
The engine went back together with new valve guides, valves and rings - all other parts were put back in and the engine just passed the 200,000 mile mark.
I really don't need any other proof that 10W-40 and/or 5W-40 works just fine.
Most rocker/cam failures on this bike are from using oil with low ZDDP levels (rocker failure) - or cam bearing failure caused by running too low of idle speed.
The bottom end probably could care less what oil is used, as roller bearings don't really need much oil to survive. The piston is somewhat similar and the piston/cylinder failures on this bike seem happen when folks run the engine out of oil.
Every now and then somebody trashes an engine when the top of the exhaust valve comes off the stem - I suspect running too big of valve clearance for too long may contribute to that failure or too lean of fuel mixture - but I really don't know for sure.
I am just going to keep running Rotellat T6 that is 5w-40.....and not worry about my oil doing a proper job.
I have had one of those highlighted in Magenta - that bike had a broken vacuum line sucking air.
Now Why did he switch to a lower viscosity oil after 60k.
Also the case we are talking about is one where the cam bearings are at the high end of the spec from having run without oil pressure for a while.
BTW that having too low of an idle causing damage is proof that pressure can get too low - but a higher viscosity oil isn't going to help there. A higher rpm idle would.
Cool.
Srinath.