According to Amsoil's testing the VI properties are:
According to Lubes and Greases GrpIII base oils are squarely in this range:
https://www.lubesngreases.com/magazine/28_2/base-oils-and-their-applications/
Source: API
Group I base oils are usually solvent extracted and dewaxed oils with viscosity indexes in the 80s, sulfur levels above 0.03% wt. and saturates less than 90%. The crude source makes a big difference in the type of Group I base stock produced. My experience with them includes a very naphthenic crude, which resulted in a 90N (very volatile), a 300N and a bright stock. I also worked with a more paraffinic crude, which produced a 100N, a mid-viscosity neutral and bright stock. In addition, there are such byproducts as lube extracts, waxes and asphalt.
Group II base oils are produced using hydrogen in a process called hydrogenation or hydrotreating. Group III base oils are made in much the same way as Group II mineral oils, except the hydrogenation process is coupled with high temperatures and high pressures. The cracked material is then separated into viscosity grades, dewaxed catalytically and finished with mild hydrotreating. The result is two or three viscosities of high VI (over 90 for Group II and 120 for Group III), virtually no sulfur (<0.03% wt) and saturates well into the 90%+ range. Because of the cracking process, no bright stock is produced and wax is relatively nonexistent. No extracts are produced, either. Group IV is reserved for polyalphaolefins, which are truly synthetic and are produced from a specific stream refined from crude.
Among the products in Group V are naphthenics. These base oils from naphthenic crudes are processed in various ways, including solvent treated and hydrotreated. There is no specific processing used or set limits on VI, sulfur or saturates. They are often distilled to various viscosity cuts without further treatment.
Group II base oils represent the majority of base oils refined in North America. The move to Group II was facilitated by the fact that a wider slate of crudes could be used and that there were less yield losses because the reduced crude was essentially “cleaned up” by the process. Less yield loss, wider crude slate processing and higher-quality finished product is a no brainer.
To a great extent, the properties of base oils dictate how they are used. In almost all cases, the finished products that are produced owe a lot to the additive technology that goes into any application. Additives typically improve the oil properties (e.g. pour point depressants), protect the base oil (e.g. antioxidants) or protect the lubricated surface (e.g. corrosion inhibitors).