I'm not trying to start competition between brands with this thread. Was just curious about what some of the members thought about my plan. I plan on changing oil in my toyota Highlander this weekend. Car has always had dino 5w-30 and fairly extended drains (about 7,500 miles). I plan to switch over to full synthetic. Will be going on vacation soon and truck will be filled to capacity with luggage, etc. I have 5 Qts. of Amsoil 5W-30 left over. But was thinking of using Mobil1 5W-40 (truck and suv) oil for this change and leave it in the rest of the summer. I would then change and use amsoil for winter. Is this being to anal? Should I just use the amsoil now instead of buying the mobil1?