Oil change info

I use 75W90 in the XJS, since 2009. Same oil I’ve been using in my EMD SD45-2 six-axle, since 1974. Never an issue in either one.

I assume you mean in the differential.
I was primarily asking about the engine oil, as it appears Jaguar specify 20 and 30 weights for the 4.2 Litre, winter and summer, respectively, other than in tropical climates, where they specify 40 weight.

It goes in the engine. Fun fact “gear oil” viscosities are calculated differently. Comes out clean as it went in.

I am aware of the discrepancy between engine and gear oil viscosities. Does that oil have any EP additives that don’t agree with engine bearing material and noting you say it comes out as clean as it goes in…where are the carbon and other combustion by-products going?

Engine oils have detergents and dispersants specifically to deal with the contaminants and absorb them into and then suspend them in the oil, which goes black as a result.
Clean oil at the end of a service life is a bad sign, it should be black.


Yet it oils, somehow, so it’s simply not such a big deal. Engine oil should definitely come out black though.

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What do you think of the 4.2L spec being 20/20W for winter and 30 for summer, only going to 40 for tropical?

I’m just being a goofball since this thread appeared to desperately need some derailing. The xjs gets 10-40. Was baiting for someone to ask me what i’m doing with a locomotive.

I have ten vehicles, 9 of which are driven. After consulting the recommended viscosities, this is my PRIMARY consideration: How old and tired is the engine?

a) Lots of blow-by, reduced compression from spec, idle oil pressure a little on the low side? It gets higher viscosity, up to maybe 20w50. My Corvair and Dodge land-yacht seem to like this.

b) On the other hand, if it’s healthy, I follow manufacturer recommended. My other vehicles fall into this category.

Life is simple unless one is determined to make it less simple. I fall somewhere in the middle, since it can be amusing to un-simplify at times.


Awesome, and I didn’t even question you! I opine that you should use a SAE40 in your locomotive, though.

Loco specs say you must use SAE 60 in mountainous terrain.

Please drive safely.

Do additives improve engine oil performance?
Well worth watching.

If You LOVE One Of These Additives, DON’T Watch This Video! (youtube.com)

Back on track :smiling_face_with_tear:

You’re going to love this one then… :slight_smile:

More Zinc = More Wear? The REAL Truth About ZDDP Additives (youtube.com)

The creator is a trained and qualified Tribologist, who used to work at as an oil blender. When I first saw his videos I found them too “American” in presentation, but now He’s found his stride and the information is solid.

ZDDP creates acid, which can cause catastrophic damage in only a few minutes.