I know M1 seems to be the synthetic of choice for our Vibe BUT one can buy a case of 6 quarts of PP for $28.86 + tax at _Sam's Club_ ie $4.81 per bottle. At Crappy Tire it would go for almost $7 a bottle.
Also when they have a sale its 5L for $29.. but I think the price went up recently.. I'm waiting for a sale so I can stock up again! cheersnow if only Costco Sold Mobil1 we would get the best deal..