What is considered a respectable HTHS?

[ZeeOSix]

This makes me realize a couple things. There's a definate connection between KV100 high cSt and high HTHS. It appears to me that Euro oils are (at least in part) relying on having higher cSt @ KV100 to get a higher HTHS number.

Only a loose correlation between KV100 and HTHS viscosity. If you had no HTHS numbers for any oil, then the next best thing to do is choose the higher KV100 in the oil grade you're looking at. If you look at oil like what HPL makes, there are some lower grade oils that have way higher HTHS viscosity than the ones you can buy off the self at Walmart, etc.

 

[Lawnman23]

And to add, not by much at all. The hydraulic pumping HP difference is hair splitting at best ... running the numbers shows this. Also, variable displacement oil pumps try to minimize oil flow to low as possible. I'd rather have an old fashioned oil pump that pumps way more oil flow than the minimum and I'll take the 0.05 MPG drop in fuel economy.

Do variable pumps have stages they switch between (low/med/high) or do they just try to hold a commanded pressure and variate based on load etc..?

 

[ZeeOSix]

Do variable pumps have stages they switch between (low/med/high) or do they just try to hold a commanded pressure and variate based on load etc..?

Depends on the pump design and the control logic. There are many different ones being used. The only way the oil pump could hold a constant oil pressure at some point in the oiling system is by using a real-time feedback signal from a pressure sensor that would be an input for the computer to control the pump output volume.

I don't think you'd would want a constant pressure control, because as the engine RPM goes up then there would be a need for more oil volume which means there would have to be more oil pressure required. If the oil pressure was held constant, then at higher RPM the oil volume would have to be cut back in order to keep the oil pressure constant, and that would mean less oil volume going to the oiling system at higher RPM, which probably wouldn't be a good thing.

The simpler variable output pumps would cut back the oil volume at lower RPM because not as much volume is needed at low RPM, and then kick the oil volume up at higher RPM where more volume is needed. All they are trying to do is cut back the oil volume some at lower RPM (compared to an old fashioned PD pump) to save a minuscule sliver of fuel economy. All the complexity is kind of a waste for such a small gain, and just more stuff to go wrong from complexity IMO.

 

[kschachn]

Do variable pumps have stages they switch between (low/med/high) or do they just try to hold a commanded pressure and variate based on load etc..?

The only ones I’ve seen are like the one on my Tiguan. They have a normal setting and a low, essentially two settings. If it fails high you get a “regular” CEL, if it fails low you get a flashing “stop now” CEL.

 

[Lawnman23]

The only ones I’ve seen are like the one on my Tiguan. They have a normal setting and a low, essentially two settings. If it fails high you get a “regular” CEL, if it fails low you get a flashing “stop now” CEL.

Gotcha. I assume the low setting is for low-load highway cruising and the likes. Do you by chance know what data points they use to determine when to go low? I'm sure its different amongst manufactures, just curious.

 

[kschachn]

Gotcha. I assume the low setting is for low-load highway cruising and the likes. Do you by chance know what data points they use to determine when to go low? I'm sure its different amongst manufactures, just curious.

It’s just a pressure switch on my Tiguan. I don’t know about other manufacturers.

 

[Carlostrece]

Only a loose correlation between KV100 and HTHS viscosity. If you had no HTHS numbers for any oil, then the next best thing to do is choose the higher KV100 in the oil grade you're looking at. If you look at oil like what HPL makes, there are some lower grade oils that have way higher HTHS viscosity than the ones you can buy off the self at Walmart, etc.

What is HPL? I'm vaguely aware that it's a brand of oil.

 

[Cujet]

People incorrectly presume lower.HTHS equals more wear. This is inaccurate because engineering (oil coolers, bearing design, oil pump strategy and application(commuter car vs race.track) matter by a lot.

100% correct. I was going to mention the temp aspect. First, Very few engines ever see 300ºF general oil temps. Also, in locations where oil temp can reach that high or more, such as turbocharger bearings and ring lands, the need for high viscosity may not exist.

 

[ZeeOSix]

What is HPL? I'm vaguely aware that it's a brand of oil.

Lots of threads in this forum about HPL oils.

https://www.hplubricants.com/

 

[ZeeOSix]

100% correct. I was going to mention the temp aspect. First, Very few engines ever see 300ºF general oil temps. Also, in locations where oil temp can reach that high or more, such as turbocharger bearings and ring lands, the need for high viscosity may not exist.

The need for high viscosity oil may not exist where the oil temperature is the highest? What's the meaning of your bold sentence?

The chart in post 58 clearly shows that more wear occurred in the top ring with lower oil viscosity.

 

[BMWTurboDzl]

Do variable pumps have stages they switch between (low/med/high) or do they just try to hold a commanded pressure and variate based on load etc..?

Kind of. This is how the BMW N55 operates.

 

[mitsuman47]

Have to be careful with context when talking about the correlation between HTHS viscosity and engine wear. It has to be looked at under the same conditions, like for instance the oil being the same temperature and under the same shear rate in a bearing or between two moving parts. An oil with less HTHS viscosity under those same operating conditions will result in a smaller film thickness between the moving parts, and therefore have the possibility of more wear. Wear control is all about separating moving parts with an adequate film thickness between parts to minimize rubbing and wear, and also the film strength of the oil which is what mitigates wear when two moving surfaces start rubbing on each other when the film thickness goes to zero.

Of course if you have some 0W-8 and run it though an effective oil cooler to keep the oil temperature down, then it's gong to result in more viscosity and therefore more film thickness between parts. That's just making the operating hot viscosity higher by keeping the oil cooler. But if you ran that 0W-8 at 250F operating temperature it's not going to provide the same film thickness between moving parts as say a 0W-40 or any other thicker oil would at that same 250F operating temperature. That's the context that needs to be used when comparing engine protection vs the HTHS viscosity factor.

Studies do show that more wear can result in most engine components as the HTHS viscosity gets lower ... typically when it starts getting around 2.4 cP and below. This is why engines that specify 0W-16 and lower oil grades use some special engine design features to help decrease wear when the film thickness becomes lower as the viscosity becomes lower.

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@ZeeOSix cool graphs. Any idea what’s going on with the Trailer Tow data on the Liner wear graph?

0w-16 showing almost zero wear while 5w-30 did show wear is not what I’d have expected.

 

[ZeeOSix]

@ZeeOSix cool graphs. Any idea what’s going on with the Trailer Tow data on the Liner wear graph?

0w-16 showing almost zero wear while 5w-30 did show wear is not what I’d have expected.

Don't know for sure, but look at the trailer tow test condition for the top ring wear. Big difference in wear on the top ring for that test condition.

 

[ChrisD46]

Valvoline Restore & Protect 5W30 has an HTHS of 3.2 . I also read once that once you start spirited driving (4,000 RPM’s and higher) then you need an HTHS above 2.8 . If you drive more conservatively at lower RPM’s , speeds , etc. then a HTHS below 2.8 is fine . I’m sure there is a bit more to optimal HTHS for your engine & driving style but as a general rule synthetic oils in the 3.2 to 3.5 HTHS range would be fine for many.

 

[wemay]

Valvoline FS High Mileage 5w30 has a HTHS of 3.2. The same oil in 10w30 has a HTHS of 3.3. Mobil 1 High Milage in 10w30 is 3.5. All these oils would work well in your application.

I don't believe M1HM 10w-30 is 3.5 any longer.

 

[Jetronic]

I don't believe M1HM 10w-30 is 3.5 any longer.

what's the kv100 of M1HM? realistically, you'd need to be very close to 12cSt t reach 3.5 cP HTHS.

 

[kschachn]

And to add, not by much at all. The hydraulic pumping HP difference is hair splitting at best ... running the numbers shows this. Also, variable displacement oil pumps try to minimize oil flow to low as possible. I'd rather have an old fashioned oil pump that pumps way more oil flow than the minimum and I'll take the 0.05 MPG drop in fuel economy.

And look at the (typically) complicated kludge that BMW implements. On strategies such as that, one wonders if the cost to implement exceeds the savings for the consumer. Sure it bumps the EPA or European tests, but that's a different outcome than providing the owner with value.

This is where it is heading these days. Engineer and implement expensive and overly complex management systems that garner an increase in corporate economy but are overall a detriment to the owner.

 

[TiGeo]

The only ones I’ve seen are like the one on my Tiguan. They have a normal setting and a low, essentially two settings. If it fails high you get a “regular” CEL, if it fails low you get a flashing “stop now” CEL.

Mine failed. They fail "high" is how I understand it. Not even a CEL...only showed with a scan.

 

[kschachn]

Mine failed. They fail "high" is how I understand it. Not even a CEL...only showed with a scan.

View attachment 288753
View attachment 288755View attachment 288754

Yep mine failed too. I got a CEL one day and I cleared it after finding out what the issue was. It came back eventually but it took a while even though like you the failure showed in the scan. I replaced the valve with a Vaico one, so far so good. The original one was also leaking.

Looking back I got a different code, mine was P06DC00 which says "Engine Oil Pressure Control Circuit High". At first I was concerned it might be a wiring fault or ECU issue but replacing the valve made it go away.

 

[TiGeo]

Yep mine failed too. I got a CEL one day and I cleared it after finding out what the issue was. It came back eventually but it took a while even though like you the failure showed in the scan. I replaced the valve with a Vaico one, so far so good. The original one was also leaking.

Looking back I got a different code, mine was P06DC00 which says "Engine Oil Pressure Control Circuit High". At first I was concerned it might be a wiring fault or ECU issue but replacing the valve made it go away.

Mine leaked as well into the connector. I ended up replacing it a second time but it was the connector not valve. Some brake clean to clean it out and it hasn't come back.