I have always used factory fills in our Vipers...BUT, as some of those oils have been "dumbed down"...and, to simplify logistics at my house...all Vipers have/will get Mobil 1's 0W-40 from now on. I have arranged a "deal" with a local distributor to discount this particular oil to VCA (and PCA) Members in our area. Prices are creeping up now, but at my last purchase time, one quart of Mobil 1's 0W-40 cost between $0.75 and $4.50 LESS than the price at Walmart, 3 national autopart chain stores, and dealership parts departments. I can also purchase as much as I want with a (minimum of 6 quarts)...plus no waiting or coupon clipping. Works for ME !!!
Our local Walmarts are stocking far fewer 5 quart jugs...AND, last week the price was $26.00 per 5 quart jug of Mobil 1's 5W-20, 5W-30, 10W-30, and 15W-50.