Can too thick of oil be damaging?

[RDY4WAR]

Simply put. If an engine calls for 5w-30 and you run 20w-50 instead, aside from power loss and hydrodynamic friction, can damage to the bearings, hydraulic lifters, chain, rocker fulcrums, etc... occur from an oil being too viscous for the application? This includes long term wear.

 

[Motorking]

Absolutely. Thick oil will not get into the tiny bearing clearances of modern cars, causing way to much heat and bearing wear. I once put 20w50 mobil 1 in my CTS-V that called for 5w30. It went into limp in mode while driving at freeway speeds and oil temp shot up to 245 degrees

 

[HemiHawk]

Originally Posted by Motorking
Absolutely. Thick oil will not get into the tiny bearing clearances of modern cars, causing way to much heat and bearing wear. I once put 20w50 mobil 1 in my CTS-V that called for 5w30. It went into limp in mode while driving at freeway speeds and oil temp shot up to 245 degrees


Thats pretty interesting. Same conditions with 5w30 what would the temp run?

 

[Rand]

Motorking you might not want to have
Quote

ay M uckley
FRAM
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in your sig as bots will scavenge the info and start spamming that person with email and spam phone calls.
(I removed some letters/numbers so they wouldnt get it from the quote)

 

[Piston_slap]

But what if we are talking about Chevrolet Vega's? I had one with high mileage (37K) and at oil changes my mechanic would use 1 qt of 10w-30 and 4 qts of STP. That gave fairly good oil control with the scuffed up bore and pistons. A little hard to start in Virgina winters until I installed a diesel block heater.

 

[OVERKILL]

Originally Posted by Motorking
Absolutely. Thick oil will not get into the tiny bearing clearances of modern cars, causing way to much heat and bearing wear. I once put 20w50 mobil 1 in my CTS-V that called for 5w30. It went into limp in mode while driving at freeway speeds and oil temp shot up to 245 degrees


GM has recommended 15w-50 for track use in the Corvette for years. The same engine specs 5w-30 under normal use. I'm guessing you had something else going on.

 

[tig1]

Originally Posted by Motorking
Absolutely. Thick oil will not get into the tiny bearing clearances of modern cars, causing way to much heat and bearing wear. I once put 20w50 mobil 1 in my CTS-V that called for 5w30. It went into limp in mode while driving at freeway speeds and oil temp shot up to 245 degrees



In my 1990 Ford Tempo I used M1 5-30 for the first 150K, but on a whim I put M1 15-50 in the sump on the advise of a thick oil friend. Right off the bat the engine was much more sluggish. With less than 500 miles I changed it out for my normal 5-30, and all was well. Just stick to what the oil fill cap says or a close 2nd choice. My Fords call for 5-20, but M1 0-20 specs for the Fords.

 

[Dave Sherman]

If it gets too thick, then you may have to worry about things like shearing oil pump drives. There may be a pressure relief valve, but if the oil is too thick it may not move quickly enough through the relief valve to protect things. Case in point, my MG calls for 20W-50 (in summer), but if it's 20 degrees F out and I get it started, the oil pressure will register over 80 PSI even though it has a 70 PSI relief in it. Engines with variable valve timing solenoids may not take kindly to abnormally high oil pressure. Ditto for hydraulic timing chain/belt tensioners.

 

[RDY4WAR]

I've wondered about the OEM recommendations of 5w-50 or 15w-50 with track use if that's just an overkill CYA. I could understand if the oil was reaching 275*F on long runs.

I'm talking about a daily commuter. It's a friend's 2004 Tahoe with the 5.3L V8 that's in question. He runs VR1 20w-50 in it because "If it's good enough for my Monte Carlo, it's good enough for the hoe."

 

[Ded Mazai]

It will not do any long term damage to the engine, As long as you are happy with the engine performance and the fuel consumption there are no other restrictions on using a thicker oil.

 

[supton]

I believe some of the small block Fords could twist the oil pump tang off the distributor, or somesuch, due to the heavy load on the oil pump. I think that is the only time I've heard of actual engine damage from too-thick oil.

Other engines, I'd wonder about cold starts. Try to start below the oil's lower temp and it's all the more work on the starter.

After that, it's most likely just wasted energy pumping thicker oil, and not actually damaging anything. No damage, just waste of money IMO on lower mpg. [That said, there's been reports of a few high-mile Ford 4.6's on super thick oil. And plenty on thinner oil too.

]

If it's your friend trying it out, just sit back. If it's a real problem, you'll know soon enough. At least it won't cost you anything.

 

[OVERKILL]

Originally Posted by supton
I believe some of the small block Fords could twist the oil pump tang off the distributor, or somesuch, due to the heavy load on the oil pump. I think that is the only time I've heard of actual engine damage from too-thick oil.

Other engines, I'd wonder about cold starts. Try to start below the oil's lower temp and it's all the more work on the starter.

After that, it's most likely just wasted energy pumping thicker oil, and not actually damaging anything. No damage, just waste of money IMO on lower mpg. [That said, there's been reports of a few high-mile Ford 4.6's on super thick oil. And plenty on thinner oil too.

]

If it's your friend trying it out, just sit back. If it's a real problem, you'll know soon enough. At least it won't cost you anything.


Yes, the Ford's could do it, but it was generally the result of somebody "upgrading" the oil pump to an HV one and then running 20w-50 in it. Why this became a trend I'll never know. ARP and a few others make hardened shafts for them.

 

[tcp71]

a 100C 20w50 wt oil has a viscosity of around 18CST. A 40C 5w30 oil has a viscosity around 45CST. The viscosity differences of hot vs. cold oil are so much greater than the differences between 30 and 50 wt oil at operating temperature that all our engines must explode before we hit operating temperature. Short trippers beware.

 

[Patman]

Originally Posted by tcp71
a 100C 20w50 wt oil has a viscosity of around 18CST. A 40C 5w30 oil has a viscosity around 45CST. The viscosity differences of hot vs. cold oil are so much greater than the differences between 30 and 50 wt oil at operating temperature that all our engines must explode before we hit operating temperature. Short trippers beware.


But then we also need to worry about what cst will that 20w50 be on a cold start, even on a 40 or 50 degree day. It'll be a lot thicker than 5w30 would be.

 

[RDY4WAR]

Originally Posted by tcp71
a 100C 20w50 wt oil has a viscosity of around 18CST. A 40C 5w30 oil has a viscosity around 45CST. The viscosity differences of hot vs. cold oil are so much greater than the differences between 30 and 50 wt oil at operating temperature that all our engines must explode before we hit operating temperature. Short trippers beware.


I'm worried more about after the oil heats up and is steadily pumping 18 cSt oil for an hour straight vs a 10 cSt oil.

What about HTHS? If the 5w-30 is 3.0 cP vs the 20w-50 is 5.0 cP.

 

[newbe46]

On the track the oil should warm up quicker and stay on the top end of the temperature range for much longer. I can understand the logic behind using 15W-50 in an engine that recommended 5W-30 on street.

 

[OVERKILL]

Originally Posted by RDY4WAR
Originally Posted by tcp71
a 100C 20w50 wt oil has a viscosity of around 18CST. A 40C 5w30 oil has a viscosity around 45CST. The viscosity differences of hot vs. cold oil are so much greater than the differences between 30 and 50 wt oil at operating temperature that all our engines must explode before we hit operating temperature. Short trippers beware.


I'm worried more about after the oil heats up and is steadily pumping 18 cSt oil for an hour straight vs a 10 cSt oil.

What about HTHS? If the 5w-30 is 3.0 cP vs the 20w-50 is 5.0 cP.


If anything, it is beneficial, but it certainly would do no harm. Anything hydrodynamic would experience a larger buffer of protection.

An engine short tripped in the winter in Canada will experience much thicker oil for most of its operating time than a car using 20w-50 driving around Texas. Engines are extremely tolerant in variances in viscosity, the only time it can become problematic is with an oil pressure sensitive circuit to control something like VCT or VVT and at X oil temperature it expects Y pressure. If you deviate too far on viscosity from spec what it expects for Y does not match what it should see at X and this can throw a code.

 

[slacktide_bitog]

As long as it doesn't get this thick

 

[buster]

Engines can run on multiple viscosities but there are extremes at both ends of the spectrum you should avoid.

 

[Whimsey]

In my pre BITOG days I was under the impression that with oil "thickerer is the betterer" . With my then 1 year old 1996 Zetec Contour I went from the recommended 5W-30 to using 5W-50 for 2+ years. While it didn't cause any mechanical harm it harmed my wallet with much lower mpg's. Also the power feel was noticeably less. Plus winter starts were more "challenging" to say the least. In other words I gained no benefit. I went back to 5W-30 and all was happy again, better mpg, more feeling of power and acceleration returned. This is not a race car but it's my "poor man's BMW" and I tend to drive it enthusiastically occasionally. I did an UOA at ~106,000 miles with ~8,800 miles using PP5W-30 and the results were very low wear overall for the mileage run.

Whimsey