I recently purchased a German diesel car (Jetta TDI) and was surprised to learn synthetic diesel oil (must be rated either CG4 or CH4) is required by VW for its fine diesel engines. Also, when using synthetic diesel oil, the oil change interval is increased to 10,000 miles, so this helps offset the higher cost of the synthetic diesel oil. I seem tio recall reading somewhere if one changes to synthetic oil it is not a good idea to go back to standard oil later. Please comment on synthetic oil for use in my Beta 722. Although its pretty easy to change the oil, it would be even nicer to do it less often.
Kubota's official line is that synthetic oil is fine but they say that you must still keep to the recommended oil change schedule.
As most of us only do between 50 and 200 hours a year on our engines, is makes sense to just start the sailing season with fresh oil and then when you lay the boat up for winter, change the oil to leave clean oil in the oil passages and around the bearings.
