I picked up six of the 5qt jugs of Havoline High Mileage 5w/20 from Amazon when it was on sale (about $1.88/qt). Looking to mix it with a synthetic; 3 qts Havoline HiMi to 2qts synthetic for a synthetic blend. Campbell's Supply has Havoline DS 0w/20 for $4.60 per quart. Wal-Marts individual quarts of conventional oil run $4.47 per quart. Can Havoline Synthetic be purchased any cheaper? Are there any other good choices to mix with the Havoline?