does 5w-20 thin out during use?

[CATERHAM]

Originally Posted By: Tim H.
Perhaps, but was still 5w-20...

Maybe or maybe not.
Is Red Line 5W-20 with it's HTHSV of 3.3cP a 20wt oil?
Same goes for Red LineI 5W-20 with it's HTHSV of 3.0-3.3cP.

As always take the grade on the bottle with a grain of salt particularly when talking about expensive GP IV & V formulations.

 

[mechtech2]

change. [/quote]

Actually, that Zetec engine was originally spec'd for 5-30.
After 5 years or so, it was then spec'd to 5-20.

 

[CATERHAM]

Originally Posted By: virginoil
Originally Posted By: lexus114
(tig wrote) I used Mobil 1 5w20 in 1978. In cars that I was using 10W40 in.

My point is, if it worked for tig back then. There sure shouldnt be any problems now.

Pretty knuckle headed reasoning here. "if it worked for tig back then" ?
I guess you are saying if the vehicle called for a 5w20 back in 1978 then fine,
But if the vehicle called for a 10w40 and a 5w20 was being used without used oil analysis etc then this is knuckle headed.

UOA is fine but still a little like "closing the barn door after the bull's has gotten out".
What does eliminate all risk is an oil pressure gauge. Even a 20wt oil with a HTHSV of 2.6cP is too thick in a vehicle spec'd for a 40wt oil until the oil temp's hit at least 80C. And since the maximum oil temp's in most vehicles hovers in the 80-95C range, running a 20wt oil is a non issue unless higher oil temp's are routinely seen.

 

[Whimsey]

Originally Posted By: mechtech2


change.


Actually, that Zetec engine was originally spec'd for 5-30.
After 5 years or so, it was then spec'd to 5-20. [/quote]

I think he said he had 2003 2.3 Duratech, which was most likely spec'd for 5W-20 originally. I have a 1996 Zetec and that was not back spec'd to 5W-20 for years after Ford back spec'd other older models to 5W-20. It is now back spec'd to 5W-20.

Whimsey

 

[addyguy]

It's actually suprising that Mobil 1 5W-20 worked as well as it did in the 1970's - it was a very, very thin 20-weight.

The 1979 Specs for it have been posted here, and they were 7.5cst @100C...basestock was 85% PAO/15% POE....

 

[tig1]

Originally Posted By: addyguy
It's actually suprising that Mobil 1 5W-20 worked as well as it did in the 1970's - it was a very, very thin 20-weight.

The 1979 Specs for it have been posted here, and they were 7.5cst @100C...basestock was 85% PAO/15% POE....


I first used the Mobil 1 5w20 in a 77Dodge pickup slant 6. The only differance was that the oil consumption increased a bit over the Valvoline 10-40 I first used in that engine.

 

[CATERHAM]

Originally Posted By: addyguy
It's actually suprising that Mobil 1 5W-20 worked as well as it did in the 1970's - it was a very, very thin 20-weight.
The 1979 Specs for it have been posted here, and they were 7.5cst @100C...basestock was 85% PAO/15% POE....

The KV100 spec' is not a reliable indicator of a "very very thin 20-weight" when you're dealing with POE/PAO oil chemisties.
For example Red Line 0W-10 with it's KV100 spec' of only 5.2cSt still has a higher in bearing viscosity (HTHS) than most dino based 20wt oils.

 

[UNC017]

Originally Posted By: LeakySeals

I was unaware 5w20 or 0w20 had been around long enough to make that claim. Thought only new engines were running it.


Its been OEM spec in many Fords for 10+ years now (some Chrysler engines for >5 years) and there are have been studies of Modular v8s that went from copcar to taxicab duty and regularly live to over 300k miles, frequently to much more, without oil-related issues.

 

[UNC017]

Originally Posted By: tig1

I first used the Mobil 1 5w20 in a 77Dodge pickup slant 6. The only differance was that the oil consumption increased a bit over the Valvoline 10-40 I first used in that engine.



Well, that's hardly a fair test. The fat in whole milk would be enough lubrication to keep a slant-6 running for 10 years.... ;-)

 

[tig1]

Originally Posted By: 440Magnum
Originally Posted By: tig1

I first used the Mobil 1 5w20 in a 77Dodge pickup slant 6. The only differance was that the oil consumption increased a bit over the Valvoline 10-40 I first used in that engine.



Well, that's hardly a fair test. The fat in whole milk would be enough lubrication to keep a slant-6 running for 10 years.... ;-)


The slant 6 was a OK engine, but I had Ford 6 cyl engines that were much better than the Chrysler 6. The carbs on the Chrysler slant 6 was terrible(I owned 3 slant 6s before giving up on them). Also one reason I went to Mobil 1 5w20 was the easier starting in the cold winters of Maine where I lived then, and the sludge problems I had with the 60s slant 6. Mobil 1 5w20 took care of both problems.