Not sure if the information is still valid, but heres a good piece of information that really stuck out in my head when this topic came up on a daily basis years ago.
Originally Posted By: Drivebelt
These recommendations of different weight oils for the same engine in different parts of the world has to do with the different oil basestock supplies around the world. Grp I basestocks are still predominately used outside of North America (Canada/US) -- and even in Europe. There is comparatively very little Grp II supply of basestocks outside of NA.
A couple of new Asia-Pacific plants that produce GrpII/III’s (and in Europe) have come on stream in the last couple of years, but before that there was virtually no supply of Grp II’s in Asia or Europe. Even then, these Grp II plants can only supply a very small fraction of the base oils needed if areas like Asia wanted to switch from Grp I to II basestocks for their motor oils. To put this in perspective, in 2003 about 75% of the world Grp II supply was in NA, and we just have enough Grp II supplies to meet our demand for motor oils. Some independent producers were worried about the supply of Grp II’s to meet the new GF-4 spec’s, because Grp II’s would basically be required to meet the NOACK volatility requirements and Grp I would basically almost be shut out completely. For the rest of the world, they have to use mostly Grp I’s or synthetics -- no choice. In Japan (2003) 84.4% of the oil basestock supply was Grp I -- 7.4% Grp II.
There is simply no way to make a quality 5w-20 oil from a Grp I that is going to hold up very long in an engine. Without any supply of Grp II hydrocracked oils, the only way to make a good 5w-20 would be to use synthetics -- Grp III’s and up. But then, if a manufacturer spec’s 5w-20 outside NA, they would basically be forcing these people to use synthetics -- and the cost issue comes into play. The average motorist will balk at the cost of synthetics.
Ideally, one wants to use a thinner oil like a 5w-20 or 5w-30 over a 10w40 because of fuel mileage and likely better oil circulation, but the problem is that thinner basestocks don’t hold up as well a thicker ones -- particularly with regard to NOACK volatility, and I’d imagine somewhat with regards to thermal stability. The aromatics in a Grp I break down quickly and the oil losses it lubricity causing more wear. Thinner oils also generally show somewhat more wear. So using a Grp I thinner oil is going to be like a double whammy as far as wear is concerned. One can compensate this somewhat by using higher weight oils that don’t show as much wear and hold out better. If you ‘re using a Grp I oil, you need every edge you can get in better protection. Fuel economy and the relatively very small benefits of thinner oil (few %) are of a distant secondary concern. There also is the issue that in very warm or “tropical” climates like Indonesia and many parts of the world, lighter weight oils probably won’t make as much difference in fuel mileage as in cooler climates. And, if you’re already using much smaller more fuel efficient engines to begin with (rest of world outside US) then a few % gas mileage really doesn’t really hurt that much. Engine protection becomes a more important parameter with Grp I based oils.
The problem is also compounded by the fact that Grp I oils don’t flow at cold temperatures as well as Grp II’s, so to make a 5w-20/30, you have to use thinner basestocks with I’s than if you blended with Grp II’s -- making things even worse.
Were seeing OCI’s of 10,000 miles in a lot of vehicle’s these days, and half that -- 5K for severe service. I think a 5w-20 blended from Grp I oil would be severely stretched to make 5K or much over that. With a Grp II -- no problem. I like this quote that pretty well sums up the performance gap between Grp I/II’s …
Originally Posted By:
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The inherent oxidation stability advantage that Group II stocks have for passing these tests is apparent in today’s engine oils. For example, Cummins and Chevron found that some commercially available engine oils consistently passed the MRV TP-1 after a 400-hour double-length Cummins M-11 test while others failed1 Subsequent analysis showed that the oils that passed were formulated with Group II. The oils that failed were formulated with Group I. A more recent study showed that Group I formulated oils stayed in grade only about a third as long as Group II (125 hours for Group I vs 400 hours for Group II) in heavy-duty engine oils formulated with the same non-optimized general offering package.
Grp II basestocks, because they cost the same as Grp I’s, change the equation. Why not get the benefits of a thinner oil if it protects just as well or better and costs no more. I’d take a Grp II based 5w-30 (or even 5w-20) over any Grp I based oil -- by a country mile.
https://bobistheoilguy.com/forums/posts/674209/
