Why does my engine need new oil all the time, but my wheel bearings never?

[MolaKule]

Grease is a thick mixture that holds oil in suspension for difficult-to-lubricant areas.

All of the wear by-products are taken up into the grease. Eventually the grease loads up and the wear metals displace the oil contained in the micelles.

The oil will also evapoarate somewhat as temps climb.

As High Plains explained so well, you don't have the combustion temperatures with which to deal for wheel bearings.

Assuming the bearings are preloaded properly, the only other problems are seal wear, allowing oil to leak out and dust to get in.

 

[michaelc80]

Wouldn't an engine packed with grease be a lot slower as well? Oil is significantly lighter than grease.

 

[blupupher]

quote:

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Originally posted by MolaKule:
...

Assuming the bearings are preloaded properly, the only other problems are seal wear, allowing oil to leak out and dust to get in.

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That was going to be my point. Most bearings are in a sealed environment. No dirt or moisture to deal with. Nothing to make the grease break down like motor oil.

 

[Kestas]

Actually, it should be the other way around... "I wish my bearings would run in oil, just as my engine does".

I work in the bearing industry. You'll find the larger, more expensive bearings that serve heavy duty such as paper mill roll bearings are oil lubricated. This allows recirculation of the lubricant, flushing and filtering of contaminants, and lubricant changeout/maintenance/monitoring is a breeze. This would be a near impossibility for automotive wheel bearings, hence the grease.

Though automotive wheel bearings are sealed, this seal is often breached, leading to early bearing failure. Seals wear. Any water of grit that makes it's way past the seal is in the bearing for the rest of its life. It would be ideal to change to bearing lubricant as often as needed. Lube-for-life is always a stretch, even for bearings.

Grease is basically just oil held together with a thickening agent.

[ April 19, 2005, 02:27 PM: Message edited by: Kestas ]

 

[i]

Wheel bearings take incredible amounts of abuse, and yet can keep spinning for hundreds of thousands of miles. Why can't I just pack my engine with wheel bearing grease and get on with life? Seriously, how in the world can a wheel bearing last essentially forever using the same lubrication it is manufactured with and no filtering?

 

[High Plains Drifter]

I would guess because it does not have to experience the by-products generated by an internal combustion engine.

 

[TomJones76]

High Plains Drifter beat me to it.
The combustion by-products are the killer.

 

[Ken2]

Hmmm. I've had some 200 hp, 1750 rpm fans in 130+ ambient temps where the pillow block roller bearings ran cooler with #2 grease than with oil, probably 220 gear oil. I gues it just depends.


Ken