Stoker gearbox oil for the old cast iron boxes

One of the common questions asked at efm was the type of oil to use in the old cast iron efm-manufactured gearboxes. The answer from the company was always 20 weight oil. When we were moving out of Emmaus, I found a new old-stock gallon can of gearbox oil, never opened; picture below. Yesterday, I took a 3oz. sample of the gear oil and an equal sample of 30 weight engine oil and set them on top of my boiler to warm them to the same temperature. Using a viscosity cup for my HVLP spraying unit, I poured 3 oz. of each oil through it. The results were:

3 oz. of efm gearbox oil 106 seconds
3 oz. of 30 weight engine oil 221 seconds

So, the efm gearbox oil is much thinner than the 30 weight oil.

Wonderful stoker man , that which we learn through experimentation. ps thanks for you pictorials

What oil did the 60 and 85R stokers use?

I don't know, Rob. They were antiques when I was a kid.

Might of been whale oil...

Pacowy wrote:That fits the pattern, Rob, because I run an 85R, and I was an antique when you were a kid.

Mike

Laugh it up you guys...I was just curious.

At moderate temperatures, the viscosity of an SAE 20 engine oil and an SAE 80 gear oil can overlap. Lots of people think the gear oil is thicker because of the higher number, but the grading system was setup that way to keep people from putting gear oil in engine crankcases.

Thanks for the explanation Rob!
JC says to use 75-140 synthetic oil.

Wood'nCoal wrote:JC says to use 75-140 synthetic oil.

That would work just fine. Out of all the gear oils on the shelf, 75w140 will have the highest viscosity index. i.e. It resists thickening in cold temperatures and won't thin as much at high temperatures as a 75w90 or 80w90 from the same manufacturer. I think using a synthetic gear oil is a good idea, but I admit that I'm running conventional 80w90 because I have a 5 gallon pail of it in the shop.

More important than the exact viscosity is keeping everything full of clean oil. My stoker is on track to run 1000+ hours this season, and I will include an oil change in the spring service.