Moly Fortified Grease and Bearings

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Jul 30, 2023
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While searching for plastic compatibility and moly grease I came across many post stating not to use moly grease in wheel bearings, without any context to % of moly, viscosity, or the base soap; just blanket statements. I wanted to bring up Ford actually spec's a moly fortified grease for wheel bearings, and a lot of Japanese motorcycles call for moly fortified grease in needle bearings. If you were to read through this board people would be mislead in which grease to use in these applications. I'm going to point out, read your equipment service manuals, they will specify which type of grease to use. Don't rely completely on Joe Bob I'm a mechanic at Oil is Us and we only use super tacky purple grease because it smells like eucalyptus...

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I suspect you are using Royal Purple ultra grease, its a excellent grease for most if not all automotive and industrial applications, myself I usually at home use Mystik JT-6 high temp (red) grease in wheel bearings,and the JT-6 semi-synthetic (blue) in everything else that comes my way to grease ,,at work we used Mobil SHC 100 and Schaeffer's #274 moly fortified,,which was preferred over the Mobil in certain bearings as it stayed in place better, never saw a problem with a grease with 3% moly or less in any bearing.
 
I used molybdenum sulfide grease in trailer wheel bearings for many years.
Only reason I stopped was I found a box of mystik jt-6 on the side of the road with most of the tubes intact. Free grease is hard to beat.
 
I've used Valvoline Ford spec's grease on wheel bearings over the years. I think it is only 1% moly. For me it also seems to stay in place over time longer than some of those red greases.
 
I have never heard being told not to use it for roller bearings or tapered bearings - here or elsewhere. In fact its often what is suggested.

Perhaps your confusing this with "moly grease is not for needle bearings" which came specifically from Chevron engineering some years ago and has technical merit. I wouldn't call chevron lubrication engineers "Joe Bob I'm a mechanic at Oil is Us " Thats pretty insulting actually.

Your best bet is to follow the spec of whomever made the bearing, which wasn't Ford - it was someone like Timken / Schaeffler / et al.

The concern with a needle bearing which typically is transmitting a axial load it the needles will slide rather than role, so Moly provides no benefit but a possible downside. Lots of people seem to have used moly grease in u-joint needles without issue - but there is the potential.

Vs a roller or tapered bearing on something like a axle, which has a radial force. Its both unlikely to slide, along with the moly can help protect against metal / metal contact caused by the radial loading.
 
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I don't remember where i heard it, but i've been told as long as its a grease thats 5% moly or less, its okay for roller/needle bearings.
 
Is there anything in meeting GC-LB that would prohibit using moly disulfide? If not, then to me it only comes down to meeting GC-LB performance
 
I've used Valvoline Ford spec's grease on wheel bearings over the years. I think it is only 1% moly. For me it also seems to stay in place over time longer than some of those red greases.
I think it is the amount of MoS2 in the grease that makes it a go no go as far as needle bearings go. I use Schaeffers 219 NLGI 1 for ball and needle bearings in my air tools that have a lube port and CV joints. If in doubt the 219 is an excellent grease.

The use of Synthesized Moly enables SynForce™ Green to be suitable for use in the lubrication of
rolling element bearings and can be used in those rolling element bearing applications that have
restrictions on the use of greases that contain molybdenum disulfide (MoS2).

 
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