Given news
A study of automotive gear lubes
http://www.technilube.com/brochures/...hite_paper.pdf
Regarding synthetics in general --
"the AAA study didn˙t go light on the research and took a comprehensive
look into all the factors involved."
´AAA found that synthetic oil outperformed conventional oil by an
average of nearly 50 percent in its independent evaluation, offering
vehicles significantly better engine protection for only $5 more per
month when following a factory-recommended oil change schedule.ˇ
http://blog.jackcarterchev.ca/new-st...ns-car-owners/
IMHO, motor oil is one thing, gear lube is another.
Worse - the GL rating (e.g., GL-4 or GL-5) isn't relevant to synchronized
transmissions.
I've come to the conclusion that all I know for sure is that Toyota
recommends 2.7 quarts of GL-4 or GL-5 75W90, and that's all that matters
since the rest seems to be marketing in that I can only find a single study
on the net that goes any deeper than that for transmissions.