i use royal purple sae 40 synthetic. in they're independant test it surpasses mobil 1 and all the others. and its not that expensive. check it out, www.royalpurple.com.
In my VP owners manual for a 01 4.3Gl, they recommend thier synthetic 30. 15-50 or 15-40 synthetics are also mentioned as suitable alternatives. I use Mobil 1 synthetic 15-50. A 5 qrt jug at Walmart is $22.
My original boat had a Volvo 280 stern drive and volvo recommended straight 30 weight oil. After much reserch I forged the gap and put in amsoil marine/diesal oil and after 15 years and a lot of hours I hit something hard and sheered the intemediate shaft. When I pulled her down the wear pattern and preloads checked okay and the gear wear pattern was good. I'M a BELIEVER The boat is now in the possesion of my buddy and this 1979 boat is still running and the stern drive is still alive and well. (For now hahahahhahaha)Was it the volvo drive or the oil????? My present rattling volvo drive is now out of warranty and I'll be switching this drive to amsoil even though it came with a GL5 synth oil in it.<br />Amsoil is not cheep but neither is an engine!
