I just had my engine pulled because of some harsh noises I had been hearing. The engine builder said that the main bearings were worn and it looked like they were worn because of too many dry start conditions. This is an extra car not used too much. It is started and driven infrequently. He said everything else was perfect in the engine so there was no sense in a total rebuild, just replace the main bearings. However he said unless I used it more often, the same thing would happen. So for a car that sits a long period of time, perhaps several months at a time, any advice as to oil, especially would a 0w or 5w be better than a 15w or 20w? or the opposite? I don't have to worry about cold weather. The car will never start in below 40 degree temperatures. synthetic or conventional?