Thick vs thin debate...

[Hogwash]

*Off the top of your head - 5W30 oils at the upper limit of approx. 11.5 ?

Mobil 1 High Mileage 5w30 = 11.9

Mobil 1 Truck and SUV 5w30 = 11.7

 

[demarpaint]

Quite simply:
- Engines are INCREDIBLY tolerant of going UP in viscosity. You'll not risk damage running 5w-50 for example in an engine that spec's 5w-20.
- Engines are NOT incredibly tolerant of going DOWN in viscosity. There's a point where you will exceed the hydrodynamic capacity of the lubricant under high temp/high shear conditions and when that happens, best case, you lose some bearing material, worst case, you spin the bearing, it locks to the journal, the rod comes off the piston and it exits the side of the block.

This is why manufacturer specs, particularly European ones, spec a minimum HTHS viscosity, that's the minimum viscosity that they deem sufficient under the worst case scenario to protect the rod bearings.

This is also why Honda when they started chasing even thinner oils went and widened the journals, as a wider bearing will have a higher load carrying capacity, which offsets the reduction in capacity from going to the thinner lube.

Back in the day they used to spec a wide range of viscosities that went right down to 5w-20 and gave specific temperature ranges these lubes were appropriate for as well as disclaimers about not operating in higher temperatures, avoiding highway speed...etc. Obviously, that's beyond the ability for most drivers nowadays. Here's an old BMW one:
View attachment 41319

You'll note 5w-20 wasn't suitable for ambient above 0C and an ILSAC 5w30 or 10w30 above 10C. This is because viscosity of course has a relationship with temperature. And there was of course still the risk of bearing damage if those grades were used and oil temp was driven up by extremely spirited driving, though without a oil/coolant heat exchanger it was likely the oil temp stayed well below coolant temp.

Great post! It should be a sticky!

Dropping a grade also can take away a margin of safety. Especially if fuel dilution is an issue, or becomes an issue in the event of something like an injector/injectors in need of service.

 

[RDY4WAR]

I've watched oil temps throughout the year in my vehicles, and haven't seen more than a 10°F difference in full operating oil temp between 100°F ambient and 20°F ambient. (All else equal) When the bearings are 30-50°F over sump temps, splashing on 400°F cylinder walls, and surrounded by 200°F coolant, it just doesn't care that much. The only time I did notice more than a 10°F difference was when I tried a higher viscosity (10w-40 vs 10w30) which seems logical given greater hydrodynamic friction.

I don't care so much for the KV100 by itself but prefer to look at the KV100 in relation to the HTHS as that tells you more about the quality of the base oil and VII. A KV100 of 12.0 cSt with an HTHS of 3.1 cP is rather lame compared to an oil with a KV100 of 11.0 cSt and HTHS of 3.5 cP.

 

[M104]

I'd like to add that unlike Dr. Haas, i have never ever noticed better fuel economy or increased power going thinner (on weak four bangers that is). When using 5w30 the engine was very smooth when cold and on short trips but always sounded like a can full of marbles after a long 3000+ rpm highway drive which is 80% of my driving. Sounds smoother with a Xw40 and i wouldn't be afraid to try a Xw50 when temps get hot.

 

[dlundblad]

I’m a thicker oil fan especially if the manual allows for it or if another vehicle with the same engine requires it.

 

[demarpaint]

I’m a thicker oil fan especially if the manual allows for it or if another vehicle with the same engine requires it.

I'm with you.

 

[dlundblad]

J

I'm with you.

Just in case BITOG’s independent fact checkers come after me, no a modern Corolla or equivalent doesn’t “need” a 10w60.

 

[demarpaint]

Just in case BITOG’s independent fact checkers come after me, no a modern Corolla or equivalent doesn’t “need” a 10w60.

I'll agree again. For me I run either 0W30 or 5W30 in both my Jeeps calling for 5W20. Time to hide from the fact checkers.

 

[SR5]

I don't care so much for the KV100 by itself but prefer to look at the KV100 in relation to the HTHS as that tells you more about the quality of the base oil and VII. A KV100 of 12.0 cSt with an HTHS of 3.1 cP is rather lame compared to an oil with a KV100 of 11.0 cSt and HTHS of 3.5 cP.

Exactly! I try and get the highest HTHS for the lowest KV100.

Right now I’m using Castrol Edge 5W30 A3/B4 which has a HTHS of 3.6cP, the same HTHS as some 40 grades like Mobil 1 0W40

 

[SR5]

I'm guessing it's pretty old, probably 90's. 15w40 would of course have an HTHS >3.5cP just like the LL oils on the right side of the chart that share a much broader range. My copy of J300 from 1999 shows 0w-40, 5w-40 and 10w-40 with an HTHS lower limit of 2.9cP, so that's likely the driver, which makes sense. The only non-LL and non-OEM grade that could be counted on having an HTHS of 3.5cP or higher would be the 15w40.

Yes, from what I can tell 15W40 has always been treated as a heavy duty or truck/diesel grade and held to a higher HTHS standard than the lesser PCMO 40 grades. It still is to this day under J300.

Mobil 1 0W40, HTHS = 3.6 cP
GTX 15W40, HTHS = 4.0 cP

 

[bbhero]

Quite simply:
- Engines are INCREDIBLY tolerant of going UP in viscosity. You'll not risk damage running 5w-50 for example in an engine that spec's 5w-20.
- Engines are NOT incredibly tolerant of going DOWN in viscosity. There's a point where you will exceed the hydrodynamic capacity of the lubricant under high temp/high shear conditions and when that happens, best case, you lose some bearing material, worst case, you spin the bearing, it locks to the journal, the rod comes off the piston and it exits the side of the block.

This is why manufacturer specs, particularly European ones, spec a minimum HTHS viscosity, that's the minimum viscosity that they deem sufficient under the worst case scenario to protect the rod bearings.

This is also why Honda when they started chasing even thinner oils went and widened the journals, as a wider bearing will have a higher load carrying capacity, which offsets the reduction in capacity from going to the thinner lube.

Back in the day they used to spec a wide range of viscosities that went right down to 5w-20 and gave specific temperature ranges these lubes were appropriate for as well as disclaimers about not operating in higher temperatures, avoiding highway speed...etc. Obviously, that's beyond the ability for most drivers nowadays. Here's an old BMW one:
View attachment 41319

You'll note 5w-20 wasn't suitable for ambient above 0C and an ILSAC 5w30 or 10w30 above 10C. This is because viscosity of course has a relationship with temperature. And there was of course still the risk of bearing damage if those grades were used and oil temp was driven up by extremely spirited driving, though without a oil/coolant heat exchanger it was likely the oil temp stayed well below coolant temp.

^^^^^^^^^^^^^^^^^^^^^^^^^

Like other guys have said....

This is an outstanding post.

 

[adams355]

I'd like to add that unlike Dr. Haas, i have never ever noticed better fuel economy or increased power going thinner (on weak four bangers that is). When using 5w30 the engine was very smooth when cold and on short trips but always sounded like a can full of marbles after a long 3000+ rpm highway drive which is 80% of my driving. Sounds smoother with a Xw40 and i wouldn't be afraid to try a Xw50 when temps get hot.

A reputable engine builder did a back to back test with a 400hp V8 in Australia with 5w40 and 5w30 on an engine dyno, there was a difference of 6hp. He did at as a proper test, not to sell anything.

 

[BISCUT]

Exactly right Biscut...

You know who was called Biscuit ??

William "The Refrigerator" Perry....

Nickname given to him by the Chicago Bears Dan Hampton who said William was only 1 Biscuit shy of 350 pounds....

I remember that beast well! 1985 He tore it up. Back then he added the exclamation point to the sad Patriots Superbowl when he ran one in.

The devil is in the details though. "Biscut" is street slang. I t was a term I heard as a young cop and thought it was funny. You correctly spelled what most people think of when "biscuit" is stated.

https://www.urbandictionary.com/define.php?term=biscut&utm_source=search-action

 

[aquariuscsm]

I’m a thicker oil fan especially if the manual allows for it or if another vehicle with the same engine requires it.

Same here. The Acura TSX has the same engine as my Accord and specs 5W30. I've been using 10W30 for almost as long as I've had it. I have a used oil analysis with it showing 0 wear metals.

 

[tblt44]

*Off the top of your head - 5W30 oils at the upper limit of approx. 11.5 ?

I consider any oil over 11 to the higher side.
Pennzoil syn for example to the low end

 

[OVERKILL]

I've watched oil temps throughout the year in my vehicles, and haven't seen more than a 10°F difference in full operating oil temp between 100°F ambient and 20°F ambient. (All else equal) When the bearings are 30-50°F over sump temps, splashing on 400°F cylinder walls, and surrounded by 200°F coolant, it just doesn't care that much. The only time I did notice more than a 10°F difference was when I tried a higher viscosity (10w-40 vs 10w30) which seems logical given greater hydrodynamic friction.

I don't care so much for the KV100 by itself but prefer to look at the KV100 in relation to the HTHS as that tells you more about the quality of the base oil and VII. A KV100 of 12.0 cSt with an HTHS of 3.1 cP is rather lame compared to an oil with a KV100 of 11.0 cSt and HTHS of 3.5 cP.

My M5 had a thermostatically controlled oil cooler and oil temps ran significantly cooler in the winter months than it did in the summer, it was interesting to observe. Both our current vehicles have coolant/oil heat exchangers so coolant and oil temp track very close together.

 

[edyvw]

I've watched oil temps throughout the year in my vehicles, and haven't seen more than a 10°F difference in full operating oil temp between 100°F ambient and 20°F ambient. (All else equal) When the bearings are 30-50°F over sump temps, splashing on 400°F cylinder walls, and surrounded by 200°F coolant, it just doesn't care that much. The only time I did notice more than a 10°F difference was when I tried a higher viscosity (10w-40 vs 10w30) which seems logical given greater hydrodynamic friction.

I don't care so much for the KV100 by itself but prefer to look at the KV100 in relation to the HTHS as that tells you more about the quality of the base oil and VII. A KV100 of 12.0 cSt with an HTHS of 3.1 cP is rather lame compared to an oil with a KV100 of 11.0 cSt and HTHS of 3.5 cP.

^This.

 

[RDY4WAR]

A reputable engine builder did a back to back test with a 400hp V8 in Australia with 5w40 and 5w30 on an engine dyno, there was a difference of 6hp. He did at as a proper test, not to sell anything.

That's reasonable. In what I've seen on the dyno, it's ~1% for every 4-5 cSt increase in viscosity. This is rough though and is dumbed down from HTHS which was the greater factor in power loss. The higher the HTHS, the sooner the rings transition into full fluid lubrication regime, but also the power loss increases exponentially as piston speed increases. In a certain 358ci V8, the difference between a 0w-20 (HTHS = 2.7 cP) and a 5w30 (HTHS = 3.4 cP) was double digits at 8000 rpm and 280°F sump temp. Blow-by also increased due to the increased film thickness causing ring flutter above 8000 rpm. This is not a casual commuter engine though.

 

[Hall]

Same here. The Acura TSX has the same engine as my Accord and specs 5W30. I've been using 10W30 for almost as long as I've had it. I have a used oil analysis with it showing 0 wear metals.

How often do you see 0º F temperatures ? You're in the Dallas area, so you don't, which means there's no difference between 5w30 and 10w30 oil.

 

[kstanf150]

Mobil 1 High Mileage 5w30 = 11.9

Mobil 1 Truck and SUV 5w30 = 11.7

Redline 5w30
12.0 and
3.7 HTHS