What I am relaying here is from personal experience in maintaining my car through the years as well as learning new concepts in auto care as time marches on. It used to be so simple, just pick a good oil, 10-30 weight for winter and a 10-40 weight for summer. Not so anymore. New car engines require altogether different oil now. Years ago in an effort to be frugal and extend my cars life as long as possible I switched to synthetic oil. I used a low viscosity oil (5-30) and found the added benefit of increasing my gas mileage another three miles per gallon. When I got my next car I was surprised to see car manufactures have engineered the new engines to run on very low viscosity oil.
Today the rule of thumb is to use oil with a viscosity of 0 or 5 – 20. I mistakenly used a 5-30 weight oil in my new car and found my mileage go from 27 mpg: to 26 mpg:. Not a huge difference, but imagine if I used a 10-40. By the way I maintain a website devoted to auto parts, if you are looking to save the most money possible and don’t mind getting your auto parts delivered you should give me a try. You will save you unbelievable amounts of money. One final thought, the old-timers had it wrong, you don’t have to change your oil every two or three thousand miles. They also recommended changing your oil filter every other oil change, do you believe it? Today’s oil, under normal use doesn’t break down as quickly so they have a longer life. Most of you probably know this but of course many people don’t, so I hope I have helped.