600w............enough is enough!

[Uncle Bob]

I wish.........


Hardly a week goes by that we don’t have at least one thread inquiring about 600w lubricant in some form or other. The variety of responses, while well intentioned, are usually not very clear because of a mix of often repeated misinformation, and some fact or sufficiently close to fact. Many attempts by several on these boards to give accurate info are often overwhelmed by a variety distractions particularly injecting the use of “magic in a bottle” additives, but not restricted to that. So, here’s my attempt to help by sharing a couple of legitimate standards in the lubrication industry that SHOULD (but, sadly, likely won’t) set an accurate baseline.


The first is something called a Data Sheet. These are publications by the lubricant producers that spell out technical data as well as typical application information. In this particular case, 600w (or more completely, 600w Steam Cylinder Lubricant) is a trade name owned by Mobil Oil, today known as Exxon Mobil Corp. This product (in evolving formulations) has been in existence for over 100 years, thus it’s reference as a lubricant for vehicles 80 years old. For those interested you can make a copy of Mobil’s data sheet here: http://catalog.mooreballiewoil.com/Asset/pds-76.pdf Just right click with your mouse on the document and click “print”. The data sheet gives all manner of information (too much some would say), but it clearly answers the frequently asked question regarding viscosity grade. This particular product is what’s known as an industrial oil, as opposed, for example, to an automotive oil. As such they use a different nomenclature for viscosity grade (think of it as a different language wherein there are different appearing terms that mean the same thing or close depending on context). This particular product is especially confusing for the partially informed because of the 600, and especially, the “w”. When automotive guys see a number value in the nomenclature they immediately think “viscosity”. However, in this case, that 600 doesn’t equate to any currently used viscosity nomenclature. Then there’s the “w”……………………………WARNING; RANT WITHIN A RANT……….Real lubrication authorities will NEVER use the term “weight” in reference to viscosity grade………….NEVER (well, unless they stoop to pandering to improper colloquialism for the sake of communication). You’ll never see the term “weight” on an official oil company data sheet in reference to viscosity. When you see a “w” in any product name or viscosity designation it means something else……………..NOT weight. (Any of you familiar with concrete products will recognize a similar reaction when the ill informed refer to concrete as cement……..or in your area of expertise something similar).

Which brings us to the second reference document. Go to the picture below, click on it to enlarge, it is a Viscosity Equivalent Chart. This is useful in comparing the different “languages” of viscosity grading where in you can see the equivalent viscosity grade of an automotive gear lube (for example) when compared to an industrial viscosity grade. So, to work from the 600w data sheet, it self identifies as an ISO 460 grade, which lines up with an SAE 140 gear lube. Now, some confusion may occur to the observant. An ISO 680 (more viscous than an ISO 460) also translates to an SAE gear lube 140. This occurs because the SAE gear lube specification encompasses a wider range of viscosity measurement than each of the ISO grades. Think of it as an ISO 460 is a “light” 140, and an ISO 680 is a “heavy” 140 (this is me pandering to colloquialism). So, which is “right”. Technically they both are, but that’s where operating conditions form the context. Those that believe “more is better” will go to the high end. Those that are aware of operating conditions might correctly understand that, as an example, in a cooler climate the more viscous product will cause unnecessary fluid friction and reduced lubrication performance.


So, does using the term “600w” mean that only the Mobil product would be correct for the stated application. No, not really. With accurate understanding of lubricant data there are alternate cross references. Most industrial oil producer/marketers have a “steam cylinder” oil, probably very similar to the Mobil formulation. And as some have learned empirically, there are other brand/types of lubes that perform in automotive applications just as well. Which is not to say that ONLY comparing viscosity grades is adequate to determine a suitable substitute. There are other considerations, most notably additive chemistry, but again, the data sheet will often be your best friend there in conjunction with a little education.



This posting isn’t intended to be all encompassing, as stated in the first paragraph it sets a baseline of accuracy from which to expand if necessary. At which point I will bite my cynical tongue and not say what I’m thinking about that.