wondering what you all have for thoughts and experience(s) with high-effieciency oil filters? are they necessary, a good investment? worth the extra $$$ or?

- i think the regular oil filter for the 3306 (and maybe other engines) is about 20 microns...is that sufficient?

I always like to use OEM filters if available, they are designed and and engineered for the engine model or component. To most people its just a matter of "it's good enough" or "it's cheaper". There is some good brands out there, Wixs, Fleetgaurd, etc, also.

I agree with Rome.  The study of oil filtration would fill many libraries when one considers micron size, efficiency, full flow and by-pass combos, filter life, chemical decomposition etc. Most machinery and engines are designed with the proper filtering system based on the intended use. 

A auto mechanic I knew that worked at a chevy garage had a small chevy car with 300K + miles on it, he used the cheapest oil available that meet the spec but always used a AC Delco filter and changed the oil at factory recommendations. He always preached quality filters and proper change intervals.

I am satisfied with the Yanmar filters. I even bought an original OEM part from this site. The original part extends life and becomes cheaper in the long run It is definitely worth the money.
originalparts4you.com/yanmar

there is a assumption that genuine parts are dearer this is not always the case.
the 7/8 button type grease fitting are case in point getting them from the dealer is much cheaper than aftermarket $7.50 instead of $21.00 in that case its simply cat or the dealer is passing on their bulk buy savings.

and some aftermarket filters are identical to the genuine as they are made by the same company this is the case for ryco filters ryco supplied the oem parts to most of the australian car makers. the difference being the paint.

its the same with gates belts and hoses the difference is the printed logo and the box.

-not much love for the high efficiency filters...i suppose a quality filter will suffice, quality oil, changed at regular intervals is the go !