How Important is HTHS?

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BTLew81

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Disclaimer...I am just curious about this. My car is under warranty, I know. I am just curious...

VW502 spec has a min HTHS of 3.5, IIRC. I'm not one to blindly run any oil, but I guess my question is this. How important is HTHS in a daily driver? My car gets driven 10 miles each way to work, highway runs once a week, and a trip once a month of 400 miles each way with a trip computer reported average speed of 70MPH. The trips include crusing at 70-80 for 3-4 hours at a time.

The reason I ask is that there are several good Xw30 oils that have HTHS of around 3.1-3.3 and are available locally at good prices. Is it safe to say that the average Joe could use these oils at factory suggested OCI's and have a long healthy life for the engine? I would think yes, but I am very interested in your thoughts. The oild that comes to mind would be PP/PU. GREAT oil, easy to source, and in my mind, would probably work quite well.

Again, interested in your thoughts!

Thanks.
 
I suspect, in day-to-day NA driving, there is very little importance in having a HT/HS value over 3.5.

On the German Autobahn, with a 2L engine in a compact car, with 4 people on board, in the summer, at 70-90mph......I'd imagine it becomes a lot more improtant!
 
A great oil like PU even seems to shear very easily. I would follow the spec. M1 0w40 can be had for good prices all of the time. I would stick with the spec for your engine. The manufacturer specs certain parameters for a reason and I would stick to it.
 
The VW spec is much more than HTHS, though I think that's an important part of it. I have always suspected the higher HTHS requirements for German cars are related to the whole "high speed autobahn cruising" thing.

There are 0w30s and 5w30s that offer HTHS over 3.5.
 
Personaly I'd stick with the VW 502 oil, at least until your warrenty is up.

I see you are running GC, and have M1 in mind. I don't know about your local, but when on sale, I can get either of GC or M1 0W-40 for my VW for close to the same prices as I do with PP for my Dodge.
 
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Let me reiterate...not looking to use PP or PU, just curious, as I have not read much on the necessity of HTHS.

Thanks for the input.
 
If you have an oil pressure gauge, that's an easy way to tell if a lower HTHS oil is doing its job.
 
Addyguy has this right.

Not that important for your easy commute, but for those 400 mile summertime trips, especially if your car is loaded with people/luggage, it becomes much more important.
 
Originally Posted By: dparm
If you have an oil pressure gauge, that's an easy way to tell if a lower HTHS oil is doing its job.

That would basically confirm if a lighter 3.1-3.1cP 30wt oil would provide adequate viscosity at the end of your OCI and when the oil is as hot as it ever gets.

In all likelyhood the answer is yes, particularly if you drive as most North Americans do; i.e., slow. Having said that I have yet to learn of a street application where a typically light 30wt oil doesn't provide more than adequate operational viscosity in an engine that spec's a 3.5cP oil but their is always the first time. That's what's nice about an OP gauge, it eliminates all doubt.
 
So this is a question I've been wondering about. I'm deliberating between M1 0w40, which is a great oil (lots of track duty) and M1 5w30, which appears to be not as great, but would suit my operational conditions better, IMO.

I'm running a built 4AGE motor, 11:1 compression (bumped from 9.4 using forged pistons), and cams. I do a lot of highway driving at 80mph and 4500rpm. I also put the car on track a lot.

Thanks to a recent fix on my car, my oil cooler now brings my oil temps down confortably below 230F going into the bearings (usually below 215F) under all but track conditions. Before, I was seeing 230-240F going into the bearings while cruising above 75mph. My track temps go to about 265F going into the bearings. Note, my measured average oil temp rise (oil going into the cooler) is around 5-10F on the street, and as much as 25-30F on the track. I realize that localized peak oil temps in the motor will be higher than that...

With the new cooler temps on the street, I decided a 30 weight would be optimal, and M1 5w30 looks like a good option, as far as weight is concerned. I know the 0w40 is likely the superior base stock oil... It has a 3.8 HTHS vs the 5w30 having a 3.1 HTHS.

So, my motor is an old design (was rebuilt 20kmi ago), it's a high revving Toyota motor, that didnt spec any VW 502.XX whatever... I'm currently running oil analyses and trying to be as scientific as possible, comparing the oils. I'll compare them on track (briefly) and street only. For track use I'm sure I'll want to continue using the 0w40, but overall, and for highway use at lower operating oil temps, the 5w30 seems perfectly optimal.

I'm planning on 5000mi OCIs.

Please advise...


Also, how does an oil pressure gauge help in this situation?

And could someone mention a few "great" 30 weight oils that having great HTHS also? Thanks.
 
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OP gauge is "measuring" the High shear rate viscosity in the deed area, and the closing clearance part of the bearing...it doesn't tell you anything at all about where the viscosity matters, in the region of MOFT.

Chances are you'll be right, but guessing (even with an OP gauge) is simply making a more educated guess.
 
Originally Posted By: dparm
The VW spec is much more than HTHS, though I think that's an important part of it. I have always suspected the higher HTHS requirements for German cars are related to the whole "high speed autobahn cruising" thing.

There are 0w30s and 5w30s that offer HTHS over 3.5.


The OP should try this Relative Performance Tool from Lubrizol.
Just add the specs an oil says it meets to the spider web. This will give you an idea of what performance parameters the OEM's are looking for.

http://origin-qps.onstreammedia.com/orig...p/pc/index.html
 
Originally Posted By: dparm
If you have an oil pressure gauge, that's an easy way to tell if a lower HTHS oil is doing its job.


What's an oil pressure gauge going to tell you about lubrication condition at cams and rings. As far as I can tell oil pressure vs hths is only going to translate to bearings.

Moreover, there's more to Euro specs than just HTHS. Among which is higher phosphorous as those engines run more lift while not using use roller-followers. And detergency and oxidation control over a longer interval.
 
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Originally Posted By: vinu_neuro
What's an oil pressure gauge going to tell you about lubrication condition at cams and rings. As far as I can tell oil pressure vs hths is only going to translate to bearings.


And with the bearings it only tells you what the HTHS is, not the lubrication state on the loaded side of the bearing (MOFT).

It's funny how on this site at present, the only engineers that you can trust are the ones who specify thin stuff...all others need to be second guessed.
 
Originally Posted By: Shannow
Originally Posted By: vinu_neuro
What's an oil pressure gauge going to tell you about lubrication condition at cams and rings. As far as I can tell oil pressure vs hths is only going to translate to bearings.


And with the bearings it only tells you what the HTHS is, not the lubrication state on the loaded side of the bearing (MOFT).

It's funny how on this site at present, the only engineers that you can trust are the ones who specify thin stuff...all others need to be second guessed.


You two could not wrote it better then you did! To choose oil solely based on oil pressure is crazy in my book.
 
Originally Posted By: Shannow


It's funny how on this site at present, the only engineers that you can trust are the ones who specify thin stuff...all others need to be second guessed.


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Originally Posted By: Shannow
Originally Posted By: vinu_neuro
What's an oil pressure gauge going to tell you about lubrication condition at cams and rings. As far as I can tell oil pressure vs hths is only going to translate to bearings.


And with the bearings it only tells you what the HTHS is, not the lubrication state on the loaded side of the bearing (MOFT).

It's funny how on this site at present, the only engineers that you can trust are the ones who specify thin stuff...all others need to be second guessed.


Those who talk loudest and most often tend to be followed regardless of what they're saying, in real life and on the internet.
 
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