发表于 2007-09-07 15:24 IP属地:未知
Group I+: Still high sulfur and low saturates, but processing conditions have been adjusted to make higher VI. This higher VI, in the range of 100-105, gives better cold cranking and Noack performance, enabling these base oils to be used in 10W-30 engine oils with minimal Group III or Group II+ correction fluids. Examples are special products from Marathon Ashland and Valero. Making these type of oils reduces base oil yield, so they may cost more than standard Group I.
Group II+: Adjusting processing conditions, several refineries can make these oils with 110-120 VI. This enables significantly improved CCS and volatility, making it possible to blend 5W-20 and 5W-30 GF-3 and GF-4 engine oils using these oils without any correction fluids. As with Group I+, the extra quality costs more to produce.
Group III+: Not available yet commercially. These will be available in the second half of this decade made from gas to liquid processes. They will have VI's exceeding 140 and will be used for 0W-XX and 5W-XX engine oils and super-premium transmission fluids.