^^^^
Interesting statement, not sure how you come up with it;
Group III
Group III base oils consist of reconstructed molecules that offer improved performance in a wide range of areas, as well as increased saturation and molecular uniformity and stability. These synthesized materials can be used in the production of synthetic and semi-synthetic lubricants.
They're high pressure hydrotreated oils from crude oil vacuum distillation. One catalyst is used to remove aromatics and sulfur. Another is used to remove wax.
Group IV
Group IV base oils are made from polyalphaolefins (PAO), which are chemically engineered, synthesized (synthetic) base oils. PAOs offer excellent stability, molecular uniformity and improved performance.
Think this group is also made by synthesizing natural gas up to lube oil molecule length. Pennzoil advertise that they are doing this. You get the same lube oil as from breaking down PAOs.
A similar lube oil can be made by putting side chains on wax molecules. Not sure this makes it a Group III or Group IV but the end result is the same as a Group IV oil. This is likely one of the blend stocks that Mobil 1 use in oils not needing PAO quality oil.
Group V
Group V base oils are also chemically engineered stocks that do not fall into any of the categories previously mentioned. Typical examples of group V stocks are esters, polyglycols and silicone. As with group IV stocks, group V stocks tend to offer performance advantages over groups I – III. An example of a mineral-based group V exception is white oil, a very pure lubricant used in industries ranging from cosmetics to food processing.
These are esters used to lube gas turbines and jets. Been manufactured for years, longer than Group III or IV ones.
Group I are solvent treated oils.
Group II are high pressure hydrotreated oils to remove aromatics but are solvent dewaxed.
It shouldn’t make all that much difference. If the thermostat and radiator is doing it’s job your summer time engine temp and winter temp shouldn’t be vastly different.
Even 20w and 30w oils will work at high ambient temperatures because ambient never goes as high as the (typically) 190 F coolant temperature that the oil "sees". Oil in a water cooled engine will operate at 210-230 F irregardless of ambient temperature.
If you followed those oil charts (and I've been at a loss to contact anyone at ASTM for an explanation as to why those upper temps are included), you'd be shutting down your tractor when it got too hot outside out of superstition.
There are VW diesels running all over the world in all kinds of climates with typically 5w30 oil in their crankcases. They've never had an engine failure due to lubricant.
