Thread: Oil recomendations for a 1990 RRC 3.9L?

I've seen all weights of oils used in these engines, personally I use a 15w40 diesel oil in all customers V8's, and I would suspect that the poor oil pressure on start up is not viscosity related, more likely filter issues, worn pump OR a problem with the timing cover gasket leaking internally where it meets the block face gallery holes, allowing the gallery to empty overnight.

Blue smoke if excessive is a worry from a Rover V8, only ones I have seen doing this have had blown head gasket/s at the upper section of the fire rings and actually suck in engine oil returning from the heads on the intake stroke, producing smoke at idle and on overrun. Also produces a fair bit more crankcase pressure, and gives symptoms similar to a broken piston/ rings without any noises.

Your oil consumption sounds acceptable, most will use up to a litre every 5000km

JC

Hi.

Would a a diesel oil not remove sludge and block up other parts of the engine due to the high detergent levels? Or start leaks?


Cheers.

My understanding is that is a very real possibilty. Oil consumption will also increase until such time as the inside of the engine is somewhat cleaner.

Personally I would stay away from diesel engine oil in a petrol engine. That is just my opinion given that oil manufacturers produce products for specific engine types, else they would make "one suits all" and they don't.

Ron.

Originally Posted by RoverP6B

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Thinner oils such as 10W...should not be used in the former type as the oil pump is not as efficient at circulating thinner oils through the engine.

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Ron.

Hmm, sorry, but that's a nonsense straight away...
If you check out actual kinematic viscosities above 0*C, some 15W-x oils are lighter/thinner than some 5W-x oils at the same temp.

Go and have a study up on how SAE oil viscosity ranges work, there's a ton of reference material IIRC in "The Good Oil" forum.

Originally Posted by RoverP6B

My understanding is that is a very real possibilty. Oil consumption will also increase until such time as the inside of the engine is somewhat cleaner.

Personally I would stay away from diesel engine oil in a petrol engine. That is just my opinion given that oil manufacturers produce products for specific engine types, else they would make "one suits all" and they don't.

Ron.

A very brief reply.

Most diesel oils are 'mixed fleet' oils, meaning they meet certain diesel and petrol engine specs.

Modern petrol specs, particularly the API SM spec and particularly GF-4 'fuel efficiency' brews have vastly reduced levels of certain additives used as basic EP (extreme pressure) and AW (anti-wear) additives in older blends, eg Phosphorous as ZDDP.

Mixed fleet/dual rated oils of CH-4 or better often use better, more expensive additives to replace these older EP/AW additives for heavy duty use, so generally speaking a diesel oil in the correct grade will protect an older design engine such as the older 3.5's thanks to the metallurgy involved, etc better than a modern SM rated petrol oil.

Sorry to ressurect an old thread. What do yo mean by better than CH-4? Newer? I can get CI-4 and an older one, forget which std butnolder than CH-4. Would this be ok? Brand is Total Rubia TIR 7400.

Yep, CI-4 or CI-4+ or ACEA E4/6

A diesel oil sporting those specs would be my pick in a V8.

Thanks! And there I was, about to use HPR30, which is fine, but diesel oil is easier to get.