All API-SL petroleum oils will be Group II or maybe with some GR-II+ base stock to meet these specs. I'm not aware of any oils made from GR-I base oils that can meet them. You might find GR-I blended in GR-III to yield the over-the-counter blends. Schaeffer blends GR-I and PAO for their blends.
Each group of base oils has some advantages and some disadvantages. I'd like to find an easy to understand reference of these points.
[ March 06, 2003, 10:51 PM: Message edited by: Ken2 ]
"All API-SL petroleum oils will be Group II or maybe with some GR-II+ base stock to meet these specs."
I thought Mobil Drive Clean was a group I with a heavy additive package. I also thought that group I had some advantages over group II, mainly greater detergency. I know the Mobil has about the worst specs of any dino oil but certainly, as indicated by its name, has great cleaning properties.
There may be some viscosities of some brands that have a majority of GR-I base. Here's what 76 (ConocoPhillips) says in a white paper:
"...the automakers opted for substantially reducing oil volatility limits from 22% maximum (by NOACK) to 15% maximum. Lower volatility means there is less potential for hydrocarbon contamination of emissions catalysts. It also means less oil consumption due to lower evaporative losses.
"In order to meet these stricter volatility limits, API SL/ILSAC GF-3 oils require the use of
higher quality base oils, especially for the lighter (and preferred) viscosity grades. SAE 5W-20 and SAE 5W-30 oils cannot be formulated with 100% Group I base oils because they will not meet the volatility limits; they require high percentages of Group II or Group II+ quality base oils. Depending on the basestock source, some Group II/Group I mixtures may qualify, while other formulations may require some Group III or Group IV base oil."
[ March 08, 2003, 12:34 PM: Message edited by: Ken2 ]