Oil Grades

[Golden bay NZ]

I came across this site and found it useful

The first page is on oil grading, but there are 8 or so other pages

[it seems they are upgrading their site. This link only takes you to their home page - just click on Oil and Lubrication on the left]

The rest of the info on this site is very basic, but the oil one is the best Ive seen

http://www.autoeducation.com/autoshop101/oil-change.htm-

An example from the site;

Abrasive engine wear can be substantially reduced with an increase in filter single pass efficiency. Compared to a 40 micron filter, engine wear was reduced by 50 percent with 30 micron filtration. Likewise, wear was reduced by 70 percent with 15 micron filtration ..."

This site really explains the benefits of a full synthetic oil. But they dont talk about changing to full synthetic from a mineral oil. From my research, this can be done safely up to 100,000 or 120,000k (no guarantees) The problem after this is that mineral oils leave a coating on your moving parts.. a full synthetic will take this coating off. So if your motor is already a little worn you may get too much vibration in your bearings etc.

Also it seems there is some confusion on what grade to use. From what I've read, 1994 year on Japanese cars need a 30 grade oil that is thin enough to squirt through the tiny feed holes. Some european cars and earlier jap cars are designed to use 40 grade oils. 50 and esp. 60 grade oils are for motors with large oil feed holes like old american v8's