What will happen to an engine if I put 15W40 in place of 5W30?

If you put 15W40 oil in place of 5W30 oil in your engine, it is likely that your engine will not run as efficiently. 5W30 oil is designed to flow better in cold temperatures, while 15W40 oil is designed to flow better in warm temperatures. This means that if you use 15W40 oil in place … Read more