Excellent question..... Re: "how long can we now go with these super base stocks and additive packages?" As our discussion has evolved, we have shear resistant base stocks, high performance additive packages, oxidative resistant lubricants but the oils are still subject to contamination from the power cycle and gear box wear. You have heard for years about doubling, tripling ODI's with synthetic oils vs. a mineral based engine oil in autos. The most significant need for changing oils IS contamination. Synthetic lubricants have the capabilities to last *much* longer than a mineral based oil but are still subject to the same contamination issues that confront mineral based oils. However, one of the prime sources of contamination is blow-by. Even in a very new, tight engine we will get some level of blow-by occuring; exhaust by-product gasses are going to get into the engine oil. Exhaust gasses will bring all manner of contaminates ranging from acids, soot, water, and even raw gasoline. With a full Group IV or V synthetic base stock, we do have significantly lower levels of combustion by-product contamination. Piston rings require an oil film for their sealing action. At & near top dead center the cylinder walls are at constant elevated temperatures. Mineral based oils continually burn off, leaving the top 1/4 to 1/2 inch of cylinder wall essentially dry, with no oil film. If you have ever overhauled a gasoline engine with many miles on it you can many times actually see this area of high wear. Correspondingly, with no oil film, blow-by occurs until the rings encounter the oil film on their trip down the cylinder wall. With the oil film, sealing then occurs. Synthetic base stocks will live at higher temps and provide an oil film nearly to TDC, thus providing an oil film for the rings to seal. Thus when ignition occurs, the rings have an oil film, seal, and very little blow-by occurs. Additionally, this is where the measurable power increase at the rear wheel occurs with synthetic engine oils. One can actually *feel* the difference in performance with the right hand! We are now deriving all of the power from combustion. And our engine oil is staying much cleaner as blow-by is greatly reduced, easily enabling doubling, and even longer ODI's on automotive/truck applications.
That said, unfortunately we have a gearbox to contend with and some Ducati have wet clutches. Both of these components add a large amount contaminants to our oil, which will create wear. Especially the gearbox as the steel wear metals will be a super abrasive for any yellow metal in our engines.. Sooo, bottom line. Yes, we could theoretically significantly extend our ODI's with the oil's capaibilities but are very much limited with the high level of contaminants the oil gets from the gearbox and clutch (if wet). So regular ODI's are in order. Hey, it's only 3 or 4 quarts..
A method to *know* what is taking place in an engine is to run an engine oil analysis to determine contaminant levels. Oil analysis is the method we use for cars, trucks and off highway equipment to determine optimum ODI intervals. In some cases we have over the road trucks going 100,000 miles between changes (filter at 50,000), with oil analysis being the driver. Then one *knows* exactly what is going on in the engine. Oil analysis kits are relatively inexpensive ($15 or so) and invaluable in determining engine status. Like taking a walk inside your engine.
George Morrison, STLE CLS
