600w vs 90w

I would definitely not use 90 gear oil in climates below zero F.
I would use 85W or 75W-90.
The best thing would be to ask other car owners and parts store people as well as mechanics.
I bought a ‘46 Ford in January one -20F day that had been sitting on a used car lot since summer.
I ruined the rear end that same day after about 20 miles.
They had to use a blow torch to get the gear oil out of the rear end.
We filled it with 80 and it lasted a few hundred miles before it got real bad.
 
Back in the day Ford recommended diluting the gearoil with 10% kerosene in both transmission and rear axle in real cold weather.
If the gear oil is too heavy (thick) it will not circulate through the cluster gear needle bearings on those cold days.
 
Kevin in NJ said:
Just stop and take a closer look please!!!

600w is a type of oil, NOT the weight or viscosity of the oil.

For the actual viscosity you need to refer to the charts for the oils.

FWIW, I used to think the 600w was the weight of the oil too.
Click to expand...

So what is the viscosity of the Ford recommended oil?
 
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.
 
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