What is it that makes gear oils smell so repulsive compared to normal motor oils?
Why do gear oils smell so awful?
- Thread starter dparm
- Start date
High Sulfur content.
also as an added incentive not to spill it when you change gear oil.
What does the sulfur do?
Smell bad! 
Sulphur and Phosphorus are smelly anti-wear additives, particularly in GL-5 gear oils for hypoid gears.
Sulfur compounds are part of the extreme pressure lubrication additive pack needed by hypoid gears. Hypoid gears are found in rear-drive differential ring-and-pinion sets where the centerline of the pinion is offset below the centerline of the ring gear- it allows for the driveshaft to be lower and the floor of the car to be flatter. The gears themselves therefore are sort of halfway between normal straight-cut bevel gears and a worm gear. That means that as the teeth engage and release, they brush across each other while under high pressure. Special additives are needed to keep the specially hardened surfaces from degrading under that kind of contact. Its a bit like flat tappet cams where you have a sliding motion and high pressure at the same time, although not quite as extreme as the tappets.
Dang. I like the smell of gear oil. LOL
Originally Posted By: Zaedock
Dang. I like the smell of gear oil. LOL
If you think gear oil smells bad, get a whiff of the limited slip additives. The odor strikes me as super-concentrated BO in a bottle, and you can even smell it through a new, sealed container.
Yeah that limited slip additive is pretty rough..
Originally Posted By: turbodieselfreak
If you think gear oil smells bad, get a whiff of the limited slip additives. The odor strikes me as super-concentrated BO in a bottle, and you can even smell it through a new, sealed container.
But despite this (maybe because of this??), it is still the #1 BEST limited slip additive I've ever used. 
I used to work on a farm and one day they had me change the differential oil in all of the old 3 ton grain trucks. It hadn't been done for about 15 years prior to that, I was told...
The smell almost knocked me out :o
Originally Posted By: Jason2007
I was told that whale sperm is used in limited slip additive and that is one of the reasons that it smells so bad. I have no idea how true that is though.
I was getting ready to say the same thing. It's probably sperm whale oil, not whale sperm.
Originally Posted By: bigmike
I'd like to see who gets the short straw on the extraction method.
hahaha. Yeah I've heard it was whale oil. I would think whale sperm would go for more than $6 per bottle..
