Originally Posted By: GMBoy
I Don't know but if it was significant I would think EP would be the Factory fill Mobil 1 oil - but it isn't for any auto makers.
It would only make sense if the manufacturer's recommended OCI was greater than the 7500-10,000 miles that XM cites for regular M1. Note that despite the fact (according to the Japanese material safety data sheets) that M1 forumulations vary from 40%-50% mineral oil for regular M1, to 10%-15% mineral oil for 0w30 AFE... XM's policy is to keep the pricing the same. ($23.50/5qt jug at Walmart.) Except for EP, which is priced higher. ($26/50/5qt)
BTW, EP is not a product in Japan, and so is not included in the data sheets. 0w20 actually only contains 5%-10% mineral oil and is a special case for pricing. Same price per quart, but not available in the jugs.
At any rate, manufacturers probably get lower pricing, with different prices for different products, depending upon actual manufacturing cost for the specific oil. If GM didn't feel that EP was required, they wouldn't pay the extra.