I have a 89 Toyota 4WD, an 01 Nissan Sentra and a 06 Mazda 2300. Looking to get all of them on one brand. Currently have the Toy on Valvoline Maxlife 10W-30, the Nissan on 5W-30 PP and the Mazda on MC 5W-20. Thinking of Havoline or MC for all of them. I do 3000 oil changes (hard habit to break).Using MC and Pur. filters... Any suggestions would be appreciated. Nissan and Toy about 10K a yr. The Mazda 25K+