The most important part of a grease is the viscosity of the oil. (ref. 10) A low viscosity oil is used to formulate a low temperature grease. A high viscosity oil is used to formulate a high temperature grease. (ref. 5) A bicycle is going to operate at a relatively low temperature. When selecting a grease for bicycle hub bearings you'll want a grease that is made from low viscosity oil. It doesn't need to be synthetic. The advantage of synthetics is that they work in wider temperature ranges than non-synthetics. They won't break down at high temps and won't solidify at low temps. Bicycles hub bearings don't experience these extremes so it's not worth the extra money.

Thickeners are three dimensional fibrous or crystalline structures commonly referred to as soaps. These thickeners act like sponges. They absorb the oil. When pressure is applied to the grease or the temperature rises, the thickener releases the oil. If the oil is not released it will not lubricate. When pressure is removed or the temperature drops, the thickener re-absorbs the oil. There are a few common thickeners that are rellavent to this discussion. They are Aluminum complex, Lithium complex, and polyurea (ref. 1, 4). Aluminum is used in marine applications. Lithium makes a great all purpose grease and is used in automotive greases. I have yet to find an automotive grease that doesn't use lithium or lithium complex as the thickener. Polyurea is the preferred thickener for use with ball bearings.(ref. 1, 3) Polyurea is synthetic and therefore more expensive to make. (ref. 4) A quote from ref. (3) "Polyurea grease has outstanding resistance to oxidation because it contains no metal soaps (which tend to invite oxidation). It effectively lubricates over a wide temperature range of -20 to 177 EC (-4 to 350 EF) and has long life. Water-resistance is good to excellent, depending on the grade. It works well with many elastomer seal materials. It is used with all types of bearings but has been particularly effective in ball bearings. Its durability makes it well suited for sealed-for-life bearing applications."

Here is a section of the Material safety Data Sheet for Park Tools Polylube 1000.

"PRODUCT TRADE NAME: PPL-1 / PPL-2
ALTERNATE NAME: PolyLube 1000 Lubricant
EFFECTIVE DATE: January 24, 2006 PAGE 1 of 2
SECTION 01 - HAZARDOUS INGREDIENTS
INGREDIENT NAME CAS NUMBER %
DISTILLATES, PETROLEUM, HYDROTREATED HEAVY NAPTHENIC 64742-
DISTILLATES, PETROLEUM, SOLVENT-REFINED HEAVY PARAFFINIC.
POLYUREA THICKENER (PROPRIETARY INGREDIENT# 28277) PROPRIETARY 5-10

As we can see the Park Tool Bicycle Specific Grease uses polyurea as a thickener. This is good because polyurea is the best thickener that you can use on ball bearings which is what is used in bicycle hubs. Remember that automotive greases uses Lithium(complex) which is cheaper but not as well suited for ball bearings. The other ingredients listed, napthenic distillates, heavy refined paraffinic, and petroleum, are non-synthetic oils. This is good because we don't need to pay the higher prices for synthetic oils for use in bicycles. Napthenic oil has to be used for the initial manufacturing of the grease because it bleeds out. Paraffinic oil is used to thin the grease to the proper consistency. Napthenic oil is chosen for dilution because it exhibits less friction. As usual, there are no absolute truths. Paraffinic oil has advantages in some respects, while naphthenic oil has advantages in others. The question of whether to use naphthenic or paraffinic oil for dilution is, however, secondary if the grease is not available for lubrication. If the oil does not bleed out from the grease, then it does not give any lubricant effect at all. (ref. 9) So far in our analysis of Park Tool Polylube 1000 we can see that every aspect of it is specific to use in bicycle hubs.

Finally we come to we come to additives. Additives are best viewed as a package because each individual additive will effect the way the other additives, oil, and thickener work. It's at this point in my research that I became very familiar with term "industry trade secret".

So we can see that "bicycle specific grease" is not just a marketing ploy used to rip us all off. But the question still remains; "Aren't there any less expensive automotive greases that will work in my bicycle hubs?" The answer is yes. The concern is that they probably won't work as well. Another fact that remains is some automotive greases are not at all suited for use in bicycles and will have disastrous consequences. The problem is we don't know which ones these are until we try them. Considering how much a wheel set costs, I'm not willing to gamble on this matter.

1) http://jchemed.chem.wisc.edu/HS/Jour...cSubscriber/V8 3N06/p862.pdf

2) http://www.engineersedge.com/lubrica...ies_grease.htm

3) http://www.usace.army.mil/publicatio...2-1424/c-5.pdf

4) http://autospeed.drive.com.au/cms/article.html?&A=0837

5) http://www.bestsynthetic.com/edu-grease.shtml

6) http://www.fammllc.com/famm/publicat...lletins_08.pdf

7) http://www.contentmart.com/ContentMa...=327&content=1


8) http://www.amstedrail.com/tech_sheets/9202.asp

9) http://www2.nynas.com/naph/start/art...=433&Sec_ID=55

10) http://www.machinerylubrication.com/...?articleid=798

This is a quote from a post of mine from this old grease thread http://www.bikeforums.net/showthread...rease+polyurea

I think the best thing I learned from that thread was that white lithium and polyurea grease are incompatible and will cause each other to break down.