Grease Separation

[Gary Schulz]

Do you guys have any issues with grease separating over time? I have been fighting an issue on the rear wheel bearings of my car where over time the oil in the grease seems to separate and migrate around the grease seal where it messes up the rear brake shoes. NO, it isn't at all because my wheel bearings are too tight and they are heating up! Wheel bearings are spaced properly and operate freely-they never get hot at all.

I think it has to do with the rather poor quality of the grease however I have tried both petroleum based grease and Mobile One synthetic and the Mobile One seems to be the worst. It separates into a red oily mess over time.

Same thing happens with my grease guns, the oil just runs out of the end of them making them a real mess to deal with!

Is there a grease that doesn't do this?

[Peter Laidler]

Interesting Gary. Never been a problem with me in my time on the engineering front line but what does seem to be a problem that I've seen and encountered is the ';'...if a little is good, then a lot is better.....' school of thought. Timken told me in a tech paper that a 1" ball of grease - just under a golf ball size of grease - is all you need in a rear wheel bearing set. Same goes for the fronts too

[Gary Schulz]

So your grease guns stay clean and the oil never runs out of them? I have tried all sorts of different grease and guns and it is always a problem for me!

[5portsrock]

I have the same with grease guns using Castrol lm, silkolene pro greases. I always put the separation down to infrequent use of the gun. I have a tub of copper crest grease which has separated. I tend to fill smaller grease guns just before use and any tubs give a mix first.

[111Robin]

So your grease guns stay clean and the oil never runs out of them? I have tried all sorts of different grease and guns and it is always a problem for me!

Same here, grease gun is always leaking out the separated "oil" but then it sits for years after being filled so probably not that surprising.

[Peter Laidler]

Re the use of the grease gun. I have to say that I was taught that the grease gun is for use only on grease nipples and not as a general greasing applicator. General grease application only from the squeeze-up/hole-in-the-middle plastic (?) pot.

In general workshop practice, to prevent any fear of contamination, anyone who left the top off the lid off the pot got a severe verbal arse-kicking especially in what we now refer to as '......sandy climates.!

[Fanfaniracing]

Same here. My grease guns always leek little bit.

At work where some 20 grease guns with different typed of grease kick allround and also in my own workshop at home...

For wheel bearings i use the SKF bearing grease for years now without any issues.

As Peter says before the amount of a golf ball sized portion of grease is enough.

I think if you grease your grease points regularly, there should arrive no issues to the bearings...

[MiNiKiN]

That's normal - grease does "bleed-out" and hence disappear over time.
In railway bearings grease is estimated to have an average life of 6 years (that includes shelf life) - we have carried out investigations on this matter with SKF UK such we we were able to to extend the service life. But it requires loads of sample taking aqnd grease analysis. So only works out if you have a large fleet running over a long time to save money on bearing overhauls and increase train availability.

So what is the message - it's a normal process even with good quality grease and grease shall be replaced every 6 years at latest.


I had old bearings, where the grease had turned into "a piece of soap" stuck in a corner of the bearing assembly. Not doing its job to lubricate any more of course. The death of any such bearing is closer than it may appear

[CooperTune]

I have been using Red Line grease for as long as I can remember and never had a problem. It is not cheap but the good stuff never is. Steve (CTR)

[bwaminispeed]

The reason the grease gets past the seals, is that the hub is a sealed chamber.......As the bearings heat up, air pressure goes up, and, unless the seal and sealing surface are perfect, it's going to push that seperated oil (and, maybe even the grease itself)past the seal.........

Simple fix, is to drill a 1/8" hole in the middle of the grease cap.......this equalises the pressure inside and out, and, everything stays where it should......

I also have a fix for the grease separation, but, am reluctant to share it, as, it is non standard to industry practice and, would worry about liability should something go wrong........

[Peter Laidler]

I'm not sure that the rear hub IS a sealed chamber BW. The actual expansion of the fluid (grease) and the air within the chamber by the heat generated within the chamber is so marginal that it could be taken up by the bellows effect within the seal. The vent hole is an answer - if pressure is a problem. And pressure can only be a problem if the grease cap is a PERFECT seal/seat within the hub. And I doubt very much that it is.

Off the subject now but one close to my brain. Grease leaching from the oil seals was a problem with Land Rovers in '.....the Gulf', where they'd be shot (if you'll excuse the pun.....) within a week, along with the xxxxxxg bearings too. Alas, there were more pressing problems with Land Rovers than grease!

Lubricants are a specialised subject all on their own, like metallurgy. But while we all talk about it, we seem to forget that oils don't loose their viscosity, they just get dirty! Oils and grease from wrecked aircraft, such as the sunken Catalinas leaking oil and petrol, recovered bomber fuel and oil tanks and fuel oil from ships (the Royal Oak is one I recall form my student days) is regularly analysed by Castrol et al as student projects and inevitably comes back as '.....could be used today.