Oil confusion????

[Fuelman]

OK, I've been reading as much as I could on these forums for a couple days now ans am truly impressed and interested in just about everything going on here. But......
This may have been covered somewhere, however what are the differences (properties, advantages, etc.) between the group I, II, III, IV, V, and whatever else is being referred to in oil basestocks? Which ones are in what oils?

Also, what is the main difference between the "high mileage" oils, "start up blends", "5000 mile extended drain" and just good plain ole oil. I take it, its the additive packages that are the primary difference, but why?
Is the high mileage oil blends going to benefit my 1995 chevy van with a 350 in it with 120,000 miles over a regular standard oil of the same brand say valvoline or castrol?

Thanks so much for helping me understand

Fuelman

 

[Ken2]

This chart will show a lot about the base oils.
http://www.chevron.com/prodserv/BaseOils/comp_med.shtml

Viscosity index relates to how much the oil thins between 40°C and 100°C. All the other criteria are pretty much self explanatory. Group V is anything not in groups I-IV. Ester compounds are usually what we refer to in Group V base oil.

Group I base oil these days is pretty much limited to industrial oils, gear oil, grease, etc., although motor oil could be made from some Group I with some Group III as a correction fluid. The oil makers have a matrix where they can blend several types of base oil, add higher cost additive packages to make lower cost base oil pass spec, and produce the lowest total cost product. Most 10W-30 will be Group II and 5W-30 will be Group II+, higher grade Group II with a higher viscosity index. Mobil 1, Amsoil, Royal Purple, and a few other synethetics are PAO Group IV. Most brands of "full synethetic" are the very highly refined petroleum Group III.

The "oil for high mileage engines" will be at the higher end of the viscosity range for the stated viscosity grade. It may also contain some esters to swell seals. Just about all oils are good for 5000 mile oil drain intervals.

For your engine, if it isn't burning oil, don't spend the money for the high priced stuff.

Ken

 

[Mamala Bay]

May consider the Delo400 10w30 if it's available. For a Chevy V-8, would give that extra protection.