My 95 V6 convert has around 240 000kms on it right now. Now, I love the car and want to keep it as long as I can. I have been running 10w-30 in the summer and 5w in the winter. I would like to go to a heavier weight for protection purposes. Is a 5w50 or mobil 1 15w50 a good decision? I was always told that the older a motor gets a heavier weight oil will offer more protection. Also, How low of a temp could I go to with the Mobil1 15w50?