I would not consider using non detergent oil at all. I would use 30w diesel rated oil, but that is just me.

I appreciate your input, but do you have a specific reason for using the detergent in a situation like mine? Unless I'm wrong in what I know about diesel rated oil, being diesel rated only means it has more detergents as additives to keep the crud in suspension, so it won't settle, then taken to the filter. Unless I'm wrong about the filtering system on this engine which was common back in the day, the oil is always being partially filtered, and that partial is small at any one time. The detergents in the oil keep the engine clean, that why it turns black so fast immediately after a change. What I don't know, and worry about is how fast it will work on the crud/sludge that has settled out already from using non-detergent oil originally. I will pull the valve cover before I run the engine, to give a hint what was used in the past. If there is a lot of sludge in there, will it cause problems if I don't change the oil very often? I don't know how fast the cleaning happens. I have cleaned old oil pans before, and that sludge in the bottom can be thick and hard.

Here is a picture of the right side of the dozer. When I saw it the 1st time in the dark, I read 4G on the engine tag and saw the D4 on the hydraulic tank. I did not see the RD-4 on the radiator. I'm not a collector, of old Cat's, I do like vintage machinery, but was looking at it as something maybe I could get to work, and use. I noticed on other D4's with a blade that they always have the blade cylinders mounted in the other direction extending toward the front, and the 4G models extend toward the rear like mine does.
 

Well I was not around in 1934/5 time, and my dad was not interested in mechanical things. But I believe they had sludge sticking the rings to cause very high oil consumption and slobbering of oil on the exhaust pipe. As the dealer was still using it as demonstrator model and bring customers to see it working, slobbering was very bad. So the dealer work on it several times trying to stop oil burning. Only successful after new improved high detergent oil was used.

Never really studied up on oil, but don't believe there is oil rated for diesel engines that is not a detergent oil. I think you are way over thinking this. But it is your tractor.

Ray, I don't see how there is any diesel rated oil that isn't full of detergent additives. Those detergent additives are what make it diesel rated. If it's as simple as not using it to protect the engine from the sludge already accumulated, that is what I'll do. Like you say Ray, people do whatever they want, and some don't even think about it at all. Diesel rated = good for diesel engines. I do know it does make a difference. Especially with 2 stroke diesels. I've see those ruined because the wrong diesel approved oil was used, but that is another subject.
That dealer that had oil slobbering on the exhaust pipe, sounds like it could have been wet stacking.

Oil - Opinions are common and everyone has at least one.

Today's oils are so far advaced from previous blends, there truly is no comparrison available.
Finding Non-Detergent is difficult.

I have had experiences with different brands of oil, some very positive and one that I will never use again, not even for lubricating a chain saw chain!

On the small farm, we ran multiple types of oil over the years in many different pieces of equipment, Never had a failure of engines. As an Example, the Thirty I was gifted, ran who knows what as it went from mulitple owners till I took it over. It has used Series 3 Standard oil, Shell Gas Engine Oil, Phillips 66 oil and others as it was changed when it was mine. Never had a failure.

One of the largest issues facing engines, is the air they breathe. The "air cleaners" were a long way from adequate or effective. The dust inhaled by those engines was the largest contributing factor to engine wear and damage.

Buy Clean Fuel - Keep It Clean was the lettering on Caterpillar Fuel Caps --- That applies to the engine and compartment fluids as well.

CTS

CTS, Walmart has had "non" in the past, but I have not bought any in awhile. I used it in a forklift transmission.

Your photos have answered a question that I have wondered about. A "D4N" winch on an RD4 tells me there is more compatibility with winches than I thought. I have the "D4" winch from my Dads old RD4 and have thought about putting it on my U series D4. I think that I have seen "D4N winches on even later model D4s than my U series. That indicates (Just my hoping) that the winches are pretty universal. If you are taking anymore photos, could you take a couple of the upper mounts and brackets for the winch. No hurry, just if you get time. Thanks, Grant.

If you have any doubts, post a photo. Non detergent oil will leave sludge wherever it pools in recesses. Usually easy to tell.
My bet is that with the prevalence of detergent oil the past 70 years it has been using detergent oil.

Hi Grant,
What I remember reading about these winches, as I knew nothing about them before I bought this dozer, is that when you ordered a winch, you also furnished your tractor's serial number and the proper mounting brackets/ plates would come with the winch. I'll take pictures for you, but the dozer isn't where I live so it depends when I'm there next. I won't forget.
I think I saw that a wide gauge tractor may have been required for the D4N. I'm sure others can clarify that.