gear oil thread
geat oil test PDF
Page 14 tells you what oil is best in high pressure anti friction and it is Redline gear oil, however that is the only group 5 oil they tested.
It has less to do with any brand as it does with what group 5 oil does for your gears.
Read here, most oils you get off the shelf that say they are synthetic, are actually group 3 mineral oil. When it comes to engine oils the argument is if it is really necessary to have such good lubrication at such a high price tag, with gear oil there is no argument. Group 4 and 5 oils are really want you want, and in my opinion group 5 is better.
Group 5 is another name for Ester or PAG, notice (in the machinelube article) that the change interval is an extension factor 5, so whatever mineral oil you put in your gears, group 5 oil will last 5 times longer. Bottom line is they do not break down, you probably will never have to change your gear oil again unless you plan on going a million miles on your truck, They do also hint at downsides, but that generally has nothing to do with time tested brands that have solved any issues with their formulations. I wouldn't trust a new group 5 without time tested users, but you can check the reviews online of any brand. The two most well known group5 are Redline or Motul. Both very similar and have loyal time tested users that go back decades.
So look at this chart, it shows an oils film strength as the temps rise. group 5 oil has around 30% greater film thickness at operating temps. That means you have better protection for metal to metal wear. In every possible test, group 5 is more beneficial then the others, plus they last longer because they don't break down as easy under temps.
PAG- group 5
PAO- group 4
Min- groups 2 and 3.
