Oil and Transmission Fluid change

[Randy]

I'm going to change the oil and transmission fluid in my 84 C-27. Should I use the straight 30 weight engine oil recommended in the manual? Or should I use a multiweight oil? (Engine is an 84 Universal M-18 diesel.)The Hurth transmission has a sticker on it calling for Type A transmission fluid. Should I use that, or one of the Dexron III products?Thanks for your help. Randy

 

[Guest]

Use recommended

I would stay with the recommended viscosity and type. Diesels don't like multi-grade oil so stay with the 30W. The trans fluid can be finicky also, so stay with the recommended.

 

[Bryan C.]

Heard both

I've heard knowledgeable sounding people say both sides of this debate. I use 15-40, because based on my experience with engines in general and comments in the Sealoc Yanmar manual (not the official Yanmar manual) a multi-grade protects an engine over a wider range of temps. But then again there is something to be said for following the manufacturer's directions! Note that the SAE rating rates the oil for different ambient temperatures. If you were running high RMPs in the tropics, 30 weight might be too thin. If you are up North in the winter, 30 weight might be too thick.

 

[Paul Akers]

Yes, but...

...an engine uses its thermostat to run at the same constant temp when it's heated up. This would tell me to run the recommended viscosity all the time because the operating temp will remain the same.I'm one to follow the Yanmar maual's recommendations.This is a good one for Gordon's comments.

 

[Gordon Torresen]

Oil changes

Things change! The 15W40 oils were not around until recently. Yanmar sold oil, in genuine Yanmar labled bottles, and all they had was 30 weight. It now comes in 15W40. I had memorized some of the mil spec letters for rating oil that are no longer in the spec book. I imagine that oil development will continue and today's letters will become obsolete. Stick with an oil designed for diesel engines.  The Hurth reversing gears all use ATFA, which is the same as Dexron.

 

[Sam Lust]

More oil

I had a very nice conversation recently with Randi Galanowski, a Customer relations representative for Castrol oil. The gist of the matter is that 15W40 made to meet API (American Petroleum Institute) classification CG-4, CG-4, CF/SJ, SH is now the way to go. Classifications CC and CD no longer exist and are considered obsolete. The "C" designations are generally for diesel, the "S" for gasoline, although they seem to overlap a lotThe problems are: "flowability" (viscosity) of the oil COLD, (most critical during cold start-up), and HOT, where a non-multigrade would loose viscosity, or thickness, allowing shear and the dreaded metal to metal at high speeds: translate to excessive wear and expensive noises. Multi-grades contain viscosity improvers which actually allow the flow of a light oil with the lubrication of a heavier oil.Later Yanmar data indicates they recommend 15W40 to API CD. They simply haven't gotten around to updating their specification to API CF or CG-4.I've run multigrade for decades now in diesels, gas and racing, and have yet to experience the first oil related problem.Go with 15W40 and be confident and happy.