Thicker oil with high mileage?

[Mr. Boston]

It's my understanding that many of the air-cooled Porsche boys are using Synthetic 20W50 Harley Davidson oil to help keep their high $$ motors happy. HD oil is *supposed* to contain large amounts of the anti-wear chemicals which the API/EPA removed for long term catalytic converter survival purposes.

 

[Curious Kid]

I suppose that is true, but of what new formulas that are out there, like in the case of the latest diesel formulations that have reduced ZDDP/Ph, it seems that the additions have made it one of the greatest oils yet - or so company's say. There's a lot working hand-in-hand, such as component composition and hardness, additive processes and so forth, so without having used oil analysis and tear-down measurements, it just might be safe to assume possible detriment. If nothing else there's always fearing the worst - that's always a drag.

Take care.

 

[glenncof]

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IMHO no, LargeCarManx2,

I beg to differ--> so long as your main and rod bearings, etc.within specifications, you can carry on using the same viscosity recommended by manufacturers even if it hits 100k, 200k, 300k, etc.

Just my 2c's worth.

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Fair enough, but as the bearing wears....material that shows up in a used oil analysis, the clearence between the crank or rod and the bearing grows larger. So a reasonable deduction would be using a thicker oil. Maybe my way of looking at this is flawed. Anyone else?

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I think both of you are right.

If maintenance has been superb, the tolerance 'could' (or 'would' in most cases) be close to original, then orignal weight is fine.

If worn then a heavier weight would be desirable from an oil consumption point of view.

I've got both cases sitting in my driveway.

 

[TallPaul]

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It's my understanding that many of the air-cooled Porsche boys are using Synthetic 20W50 Harley Davidson oil to help keep their high $$ motors happy. HD oil is *supposed* to contain large amounts of the anti-wear chemicals which the API/EPA removed for long term catalytic converter survival purposes.

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In my book, air cooled engine = Redline oil. Just put Redline 10w30 in my motorhome's generator, which just finished the factory specified break-in period. 10w30 Redline has NOACK of 6% and HTHS of 3.8. Acts like 10w40 in the bearings. Will take the heat. Gobs of zddp and moly among other things.

Redline (and possibly Maxlife because of the 300 ppm moly) are the two cases where I make exception to my signature line.

 

[sgarlic]

Feh what your buddy says. Some vehicles have great engines.. many of those old AMC 4.0 engines over 250k are still easily running 5w30 in the Jeep community. Conversely, my '96 ZJ with the 5.2 is only at 179k, but had really long OCI's by the previous owner (15k-20k or so on dino cheapest dino,) I need xW50 to keep oil pressure at hot idle.. xW40 and it'll drop off to zero (verified later on with an autometer gauge and sender) when I come to a stop. To me, it just depends on what's thinnest you can still maintain good hot idle pressure with.

 

[Lurker_Ken]

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To me, it just depends on what's thinnest you can still maintain good hot idle pressure with.

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Best answer.
Without tearing the motor down, oil pressure is a great measure of the bearing clearances.
High mileage does not mean worn bearings.
Run a thicker oil to get the oil pressure within normal operating spec.
This might be in 10,000 miles, or 100,000 miles...

Ken

 

[TallPaul]

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To me, it just depends on what's thinnest you can still maintain good hot idle pressure with.

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Best answer.
Without tearing the motor down, oil pressure is a great measure of the bearing clearances.
High mileage does not mean worn bearings.
Run a thicker oil to get the oil pressure within normal operating spec.
This might be in 10,000 miles, or 100,000 miles...

Ken

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True assuming you don't have something like a weakened oil pump relief valve spring. Anyway, I stepped up to 10w40 in my '95 F150 to get oil pressure in spec. I get 44 hot at 2000 rpm. Spec is 40-60. 30 wt gave me mid 30s psi.