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rotorwrench · 12-30-2020, 02:42 PM

One of the problems with viscosity is that fact that it is tested in more than one way depending on the application that the lubricant is blended for. Motor oil is tested in a different way than gear oil. Steam cylinder oil predated the Society of Automotive Engineers since it was developed in the mid 19th century. The SAE came about in order to set standards for products by application for the automotive industry.

The real mystery is how the term "weight" even figured into the equation since the W in the standards was meant to have a cold weather connotation or Winter (same thing). Somehow folks managed to equate that with weight and it's still common to this day.

The old 600W (of 1860 through 1931) was of no known modern standard and as such, it doesn't mean much of anything except if you did a test on it using one of the current standards then a person would know what the actual viscosity is. Personally I don't care one way or the other. Use SAE 140 if you want thick oil. STP is a viscosity builder but what does a half of a container change the viscosity of a gallon of SAE-90 gear oil to? It sort of throws the standards out the window.

Any lube is better than no lube but any good quality gear oil will do as intended. If it leaks out, go to the next thicker lube that still works.

12-30-2020, 02:42 PM	#25
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: 600w vs 90w One of the problems with viscosity is that fact that it is tested in more than one way depending on the application that the lubricant is blended for. Motor oil is tested in a different way than gear oil. Steam cylinder oil predated the Society of Automotive Engineers since it was developed in the mid 19th century. The SAE came about in order to set standards for products by application for the automotive industry. The real mystery is how the term "weight" even figured into the equation since the W in the standards was meant to have a cold weather connotation or Winter (same thing). Somehow folks managed to equate that with weight and it's still common to this day. The old 600W (of 1860 through 1931) was of no known modern standard and as such, it doesn't mean much of anything except if you did a test on it using one of the current standards then a person would know what the actual viscosity is. Personally I don't care one way or the other. Use SAE 140 if you want thick oil. STP is a viscosity builder but what does a half of a container change the viscosity of a gallon of SAE-90 gear oil to? It sort of throws the standards out the window. Any lube is better than no lube but any good quality gear oil will do as intended. If it leaks out, go to the next thicker lube that still works.