HM 5w-30 vs. 10w30 - Confused!

[SR77]

Can someone explain to me how a High mileage 5w30 can be rated as 5w oil but it is thicker then a 10w30 oil. I took a look at Castrol and Pennzoils High Mileage 5w30 specs and some other 10w30 specs and at both 40c and 100c the High Mileage 5w30s are a significant amount thicker then the 10w30. How is this possible and how can the High Mileage oils still have a 5w rating. Even though the 10w30 is a thinner oil, would the High Mileage 5w oils still be a better winter oil? thanks for all the help

 

[farrarfan1]

The new SM rated Mobil 1 is the same. The 5W30 is slightly thicker at 40c and 100c than the 10W30.11.3cst vs 10cst.This is per Mobil's website.Keep in mind that all weights are based on a scale and not an absolute number. Take 30W for example. It can range from approximately 9.5cst to approximately 12.5 cst and still be considered a 30W. So a "thin" 30W could be almost a 20W and a "thick" 30W could almost be a 40W.

 

[Drew99GT]

The HM 5w30s have a higher viscosity index then regular 10w30 and also are forumulated to pass the 5w cranking/pumping test. Try plugging the viscosities into this viscosity calculator and you'll see that despite the fact that the HM 5w30 is thicker at 40C and 100C compared to regular 10w30, it will be thinner when you get to low temps such as below 0.

 

[Blue99]

There is a group of these dino High Mileage oils that are thick 30 weights, 12cSt at 100C, and do indeed meet the 5W rating of 6600 cP max at -30C. These oils will provide better short trip/cold temp performance than a regular 10w30, probably at temps of 20-30F and lower.

I'm assuming these 5W's are formulated with additional VI improvers to achieve both the 5W rating and be 12 cSt @ 100C.

Maybe Bruce will provide us an answer based on his blending experience.

Yes, to me a 5w30 High Mileage seems like an odd multigrade, as why not just stick with a 10w30 High Mileage or the classic 10W-40, if a thicker oil is required, but evidently the market is out there, as Pennzoil & Chevron/Havoline provide this product.

 

[SR77]

Thanks for the replys. I don't know much about the specs so i will have to take another look at the specs and see what it says for the cP values. Its hard to compare the specs of a 5w and a 10w. All the different values got me confused between the two. Drew, thanks for the link, how do you use that calculator.

 

[bruce381]

It should be simple if a oil is correctly measured in vis both hot and cold then do not try to split hairs about a few cSt one way or the other.

If you think a given 5w30 is to THICK at the cold end then go to a 0w30, if you think the 5w30 is to THIN at the hot end go to a 5w/40.

The diferences between oils of different MFG as long as in grade are not worth worrying about and IMHO a waste of time.

And YES it is possible due to WIDE vis specs to have 2 5w30 PCMO's and one can be both thinner at the cold end and thicker at the hot end (higher VI) or one that is thicker cold and hot or any other combination.

Most blenders shoot for a midrange on the hot end and are happy to be in any range on the cold end

If you get to close to the "edge" your 5w30 can become a 5w/40 or a 10w/40 in a hurry and then you have to rework it but thats another story

Also a lot of oils are a result of working with what you got I would love to blend with PAO and AN but cost gets so high I can't sell it and if you are a major you use whats avalible in house mostly and whats avalible.

Also the better or higher VI base stocks used LESS VII can and is used since the base stock is cheaper than the VII makes good sense.
bruce