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**koolaid_kid** · 11-27-2011, 02:13 PM

No. Under normal conditions it would act like 140 weight lubricant. When it gets really cold the "W" comes into play and it thins to 75.

**1948man** · 11-27-2011, 02:15 PM

Thanks. I had it figured wrong.

**7981GS** · 11-27-2011, 02:49 PM

The 75W is the base weight of the oil. With additives, it can have the properties of up to a 140W oil.

You have it correct.
I use 75W-140 synthetic in all of my shafties.

Daniel

**Normk** · 11-27-2011, 07:44 PM

Another point regarding oil SAE numbers is that those for engine oils (i.e. 5, 10, 20 , 30 in the 5W-30) and the numbers for gear oils (i.e. 75, 80, 90..140 in the 75W-90) are not on the same scale.

Not sure if this is clear but what I mean to say is that an SAE 75 weight gear oil is not thicker than a 50 weight engine oil. The oil numbering system by SAE is indicative the service application of the oil and then it's relative viscosity.

This means that there is no "40" or "50" weight gear oil because the numbers "0 through 50" indicate engine oils while those "70" through "250" indicate gear oils. One purpose for selecting the different SAE viscosity range numbering is to avoid confusing the application of oils. A bottle of oil having a "90" number is a gear oil and not an engine oil.

ISO and other number systems differ but the SAE system is most common in vehicle lubricants. Two cycle oil, automatic transmission oils and other specialty oils do not use these systems.

If someone has not confirmed this difference, pick up a bottle of gear oil and one of engine oil on your next visit to a parts store. Shake the oil bottles and the difference in viscosity will be evident. One can place some containers in the fridge and then try pouring to observe the thickening effects of temperature.