Thanks Trevor, that's one piece of information I didn't have.
From: Trevor Boicey[SMTP:email@example.com]
Sent: March 18, 1998 19:54 PM
To: Dave Formstone; firstname.lastname@example.org
Subject: Re: trans drain plug tool
Dave Formstone wrote:
> Dave, gear oil and engine oil are rated on two different scales.
Just to be pedantic, they are rated on the same scale but
at different temperatures. The effect is just as you stated,
20w50 and 80w90 are about the same.
Engine oil is tested and "engine temperature" which is very
hot so the oil is thinned and rates lower. Transmission oil
is tested at a much lower temperature so it scores "thicker".