I recommend 3k for regular oil and 5k for synthetic. We don't see engine failures anymore at the dealers.When we do it's from lack of oil changes.Modern engines have alot more moving parts inside of them than older engines.4 camshafts,24 valves,24 rocker arms,24 hyd. valve adjusters,timing chains,gears,hyd.tensioners and so on.The last engine I did was a 2.7L chrysler failed from oil starvation.Half my day was spent unwrapping over a hundred new engine parts.Just the parts cost 5 grand.Also the oil pickup in the oil pan has a very small inlet screen that can clog easily.If you do any stop and go driving or short trips change the oil 3k or 5k.Why take the chance?