dcdbdave

Sorry for bringing it up this subject yet again, but after spending many hours wading through discussions about what is the best gear oil choice for the differential and not really finding SAE90, I noticed my lower unit oil for my Honda BF135hp outboard is just that. I was all set to use Mobil 75w90 but catch all kinds of back and forth, right or wrongs. I have always been hypersensitive to putting in what the manufacturer recommends and just want to get it right. Thoughts?

cosmomiller

Mobile 1 LS 75W-90 synthetic gear lube is ideal for the diff. Billman has stated a few times that he has seen it work perfectly in all S2000 diffs. I have been using it for a decade based on his recommendations. It objectively meets Honda's requirements.


https://www.mobil.com/en/lubricants/...ube-ls-75w-90/

B serious

Sure. This works. It meets all the specs in the manual. The manual doesn't state a brand...just GL5 SAE 90.

Chuck S

Pretty sure GL5 is hypoid gear oil ... but I'd not use it in the differential unless it specifically stated this on the bottle. Oil is cheap. Changing the differential is messy and smelly.

Nothing wrong with a multi-grade pure synthetic so there's no reason to not use 75W-90.

-- Chuck

B serious

but...its a hypoid gear diff. No reason this GL5 SAE90 wouldn't work.

Chuck S

Correct. Multigrades lubricate better, though, at lower temperatures. Witness the anguish about all the wear on engine startup from the oil being too thick. Where's the love for the differential?

SAE 90 grade Gear Oil was split into grades 90 and 110 after the S2000 went out of production. Current 90 is the lower half, new 110 is the upper. Old 90 covered the entire range so new-110 meets 2005 era 90 grade specs.

-- Chuck

dcdbdave

Thanks for the clarification Chuck and everyone else. I did not know the lubrication changes and also noticed my outboard oil went from SAE90 to 80w90. I will run the Mobil 75w90 and change it every other year, should be more than good.

zeroptzero

If you don't live in a cold climate and do not do winter driving the Lubrication Engineers SAE110 is perfect, it is very thick in cold temps though. UOA wear testing I did with it showed about 25% of the wear numbers I got with 75w-110 and 75w140 In warm climate driving thicker is better for the dif, diff metal wear is inversely related to viscosity which may be different than what you might expect with engine wear.

Chuck S

Has Lubrication Engineers now certified any lubes to met GL5? They withdrew certification a couple of years ago -- much discussion here.

-- Chuck

zeroptzero

Probably not because it is an industrial gear oil, so they don't go through the certification process. Much like Redline oil isn't API certified.