Which Is More Important : KV @ 100 C. vs. HTHS In 5W30 ?

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As the title states which is more important - the KV rating @ 100 degrees C. or the HTHS ( for a summer oil fill using 5W30) ?
 
for a particular grade, in this case 5W30, HTHS is the most important of the two.

Oil film thickness - more HTHS
Economy - less HTHS
 
My amateur understanding is that HTHS is the better parameter for identifying what kind of protection an oil will give you against wear and damage, especially for hot weather driving.
I know an engine in proper condition will regulate its operating temp, but this funny thing happens where I notice my highest engine oil temps always occur in the summer!
Clearly the ambient has some effect upon engine temps, there is some slop in that feedback loop.

I could be way off here and would like to be corrected by an expert if I'm wrong, but wouldn't it be desirable to make an oil with the KV100 of an XW20 and the 3.5+ HTHS of a dexos2 XW30 assuming no chemical or financial limits?
Would you be losing anything by having the oil be thinner as it circulated around the engine at "operating temp" as long as it had a good HTHS when it got heated up by friction at the metal boundaries?
 
HTHS is the most important. It approximates the conditions that is the worst in the engine. The KV100 does simulate big-end (connecting rod) low-speed driving, so it has some merit, yet physics mean if you have a good HTHS in the right range, KV100 will fall into place, so just look at HTHS by itself.
 
SAE J300 has long been in need of reform. A much better way to categorize engine oil would be xxW-HTHS.

M1 ESP 5w-30 has a higher HTHS than M1 ESP 0w-40, as an example.
 
If your engine calls for a 5W-30 and you are using a 5W-30, then both the HTHS and the KV100 will be in the acceptable range to protect your engine. If you have made engine modifications or are driving under severe conditions that could increase the potential for wear, then a higher HTHS will provide more protection.
 
*I'm thinking for a 5W30 synthetic I will see a minimum HTHS of 3.0 however if I can a 5W30 synthetic with an HTHS of 3.2 , 3.3, etc. up to 3.5 then that would be preferable ?
 
Originally Posted by ChrisD46
*I'm thinking for a 5W30 synthetic I will see a minimum HTHS of 3.0 however if I can a 5W30 synthetic with an HTHS of 3.2 , 3.3, etc. up to 3.5 then that would be preferable ?
It's usually true that small increments upward of HTHS from the absolute minimum the engine maker recommends in the Owner's Manual and/or spec allowed will result in less wear.

Wear benefits taper off. It won't hurt your engine to have extremely high levels of HTHS, yet there is no benefit, as the graph shows. ( https://www.stle.org/images/pdf/STL...and Lubricity_tlt article_July09.pdf )
 
My first summer time oil fill since becoming educated on the " documented possibility" of rod bearing issues with the 2.4L Thetta II GDI engines ... That is why I moved up to 5W30 D1 / Gen 2 / SN+ synthetic oils , so now I am looking within the synthetic 5W30 oils with the greatest film strength (to help cushion those rod bearings more ) .
 
Originally Posted by ChrisD46
My first summer time oil fill since becoming educated on the " documented possibility" of rod bearing issues with the 2.4L Thetta II GDI engines ... That is why I moved up to 5W30 D1 / Gen 2 / SN+ synthetic oils , so now I am looking within the synthetic 5W30 oils with the greatest film strength (to help cushion those rod bearings more ) .

I guess my knee jerk reaction to that situation would be to move to a 5W30 with HTHS>=3.5, or maybe a high HTHS 10W30 like the M1 HM I am using now since you are in Georgia and that would probably be fine for you all year long.
Or maybe go for an SN/GF5 5W30 like Valvoline AFS or MAG 1/Supertech/amazonbasics synth with HTHS=3.2.

The big question would be, is the nature of the rod bearing failure something on which HTHS would have an impact?
Could it be something like an inherent part strength or cracking issue that oil would have little to no bearing on? (pun intended)
 
Originally Posted by ChrisD46
My first summer time oil fill since becoming educated on the " documented possibility" of rod bearing issues with the 2.4L Thetta II GDI engines ... That is why I moved up to 5W30 D1 / Gen 2 / SN+ synthetic oils , so now I am looking within the synthetic 5W30 oils with the greatest film strength (to help cushion those rod bearings more ) .


I think Pennzoil Platinum Euro L 5W-30 from Walmart has an HTHS of 3.5. It's also Dexos 2.
 
Nothing better to gauge base oil performance then high temp hths viscosity, especially for summer oil. Doesn't matter which side of what you are serching for, gas mileage or metal protection. Want smooth engine get high hths, want that hollow no lubrication sound that will give better gas mileage in a lab, low hths is the way to go rah rah.
 
English translation:
No 5Wx20
grin2.gif
 
I ended up with Valvoline Advanced Synthetic 5W30 D1/Gen2 SN+ with an HTHS of 3.2 ... So far , very smooth from butt dyno .
 
Originally Posted by ChrisD46
I ended up with Valvoline Advanced Synthetic 5W30 D1/Gen2 SN+ with an HTHS of 3.2 ... So far , very smooth from butt dyno .

I may be going the same route with 5w20 next oc. Beginning to shy away from Pennzoil for them being shy about their numbers.
 
HTHS is where it is at. Over on the diesel side of things, it is what separates FA-4 oils and CK-4 oils of the same viscosity, where FA-4 has a minimum HTHS rating of 2.8 and CK-4 has a minimum HTHS of 3.5.
 
Mobil 1 HM 10w-30 carries a little best of both worlds. HTHS of 3.5 and a cSt @ 100c of 12.1

That is, if you don't mind the 10w over a 5w and the extra seal "conditioners" of the HM.

M1 HM 5w-30 is a decent option too, but HTHS on it is only 3.1

For summer temps, I think the 10w-30 would be fine. Not sure what you're looking to put it in however.

I use the m1 HM 10w-30 on 2 of my 3 trucks and am very pleased with it.
 
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