Mike,
I agree that "quick oil change" businesses recommendations are only to keep themselves making money. Generalizing data for a revised oil change interval won't work. The fleet operators who change oil and/or filters based on oil analysis do that analysis for each individual truck for a reason. That's because the conditions for each truck can vary. The oil that Porsche recommends has higher specifications than most synthetic oils. Go to your local parts vendor. Compare the price of Mobil 1 to Mobil 1 European specification. It's double the price, but has longer drain intervals, by both mileage and time.
One thing that I have not seen mentioned [I have not read every post] is that the vehicle manufacturers also have a calendar time limit for oil changes. That is because the anti corrosion package in oil, has a finite life span. Oil is sort of like canned vegetables in a way. In a sealed can, they both last a long time. However, once the can is opened and exposed to the air [oxygen] the life of the contents starts to count down. Another advantage of draining the oil in a gasoline engine is to get rid of any particles in the oil or sitting in the sump.
Porsche also recommends a certain calendar life for oil changes. On many Porsches [and other Euro cars] that is 2 years. Most other manufacturers use either a 6 month or 12 month calendar limit. This limit is based on how long the anti-corrosion package will last.
Our Norton engines are designed with the camshaft set high in the crankcases. Lycoming opposed cylinder piston aircraft engines also use this design. The #1 failure mode of a Lycoming small aircraft engine is lack of use. This allows the oil to drain off the camshaft. The cam and lifters then rust. Upon start up, they are damaged. To combat this, they use additive packages with high concentrations of zinc and phosphorous. Lycoming calls for oil changes every 25 hour or 4 months on engines without a modern oil filter. The recommendation goes up to 50 hours or 4 months with a modern oil filter. [This is for normally aspired Lycoming engines] Note the engine operation hour limit goes up, but not the calendar limit. Depending on the speed of the plane, 25 hours equates to 4,000 to 10, 000 miles. Both Shell and Chevron make special "storage" oils, intended to be installed into an engine when little or no usage is expected during the 4 month time limit. Lycoming has a service bulletin which calls for the addition of an additive [LW-16702] to be used in engines which had the worst camshaft issues. This additive is so good, that several aircraft oil manufacturers already formulate it into their oils.
https://www.lycoming.com/sites/default/files/The Use of Lycoming LW-16702 Oil Additive.pdf
Camguard is an aftermarket company that sells a similar additive. It meets the Lycoming spec. Perhaps this would be a good product to test? Not a useful additive for the racing crowd, but very useful to those who don't ride their bikes as often [once or twice a week, depending on climate] as they should. See
https://aslcamguard.com/
Bottom line, ride your bike regularly. Many of us should be changing our oil, not based on mileage, but on calendar time, to prevent engine damage due to corrosion. For owners where riding is seasonal, might a switch to aircraft storage oil be a good idea, during the winter?
Aircraft airframe & engine manufacturers consider coastal areas, most prone for causing corrosion. Florida and New Zealand are considered the worst! Naturally, I live in Florida. You guys who live in arid climates are reading this and wondering "What the h3ll is he talking about, corrosion?" Does Norton dictate a calendar time limit for oil changes?
Charlie K
royalpurpledirect.com
