What is the best oil for a car?

I've been using castrol syntec 5w-20 in my VW Golf tdi, it's thin as water but i get 10k miles between oil changes, I've used it since it came out and before that castrol gtx!

I've never had an oil related problem with any of my vehicles. i had an 83 Chevy Blazer, i never changed the oil in 10 years and it was still clean, i only drove several hundred miles a year, as it quit snowing here in south central Pa. I saved a ton of money on oil and filter changes! i usually change the oil every 5k miles on my gas vehicles, most are easy to change, just buy a drain pan and a filter wrench and oil plug wrench, the money you save from going to jiffy lube will pay for the synthetic oil and you know you are actually getting the oil you pay for! the thin oil disipates the excess heat better and you have less pumping friction and better gas mileage. :)