I always use a single grade 30 oil on my 235 plus the famous Mathy additiv.
I even drove a 1998 Pontiac Trans Sport (usualy needs synthethic)since more than 100.000 miles with only the cheapest multigrade I can find plus the Mathy additive. Last year I did the first oil change since I have the car (beside refill it from time to time). Never noticed any problems.
I know a guy who works on big marine diesel engines. They had to change the oil verry often, also the bearings. Since they use Mathy the double tha intervalls on oil and trippel the intervall on bearings.
That stuff is the best I ever bought and far from beeing a snake oil product.
Not sure If it is aviable in the US but here is a english language site of the manufacter.
Klick the "Mathy Test" button and do the test.
This is only a virtual test of course, but I have seen this live and pulled the handle my self.
That`s why I trust in this oil, seeing is beliving.
http://www.mathy.de/english/ Oh, I don`t get any money for that
