That's funny. In 1982 I bought an 82 Audi Coupe with the 2.14 Liter 5 cyl OHC WE engine and a manual 5 speed transmission. It had solid lifters and the service manual suggested (under normal service) that I change the oil (using API SE grade) every 7500 miles, the oil filter every 15,000 and adjust the valves every 30,000. For the next 14 years (along with all the improvements in oil quality) I changed the oil every 5,000 miles using standard dino oil that meets the current specifications (which are better than those called out in the owners manual), the oil filter every 10,000. (Of course it was a stock vehicle unmodified from the day it was built) Well, after driving the car 90,000 miles and wasting several valve cover gaskets (at 30,000 mile intervals) without making a single valve adjustment, I figured I was doing something right, and stopped checking the valve clearance which never needed any adjustment from day one. At 210,000 miles I sold the car (there was no sludge anywhere in the engine and it didn't burn any oil) which still met it's initial fuel mileage specs and met the local emission standards to my neighbor who later moved and I have no further history about the vehicle. It's just one car, but as an engineer myself I can tell you that the those at Audi who engineered that car were pretty conservative, as long as you keep up on the maintenance. IMO, those who whine about sludged up engines are like the obese guys who swear that they don't eat too much while insisting that they regurlarly work out. Please, . . . it's insulting to those of us who know better. Call the local news media, they're the only ones dumb enough to listen. My next Audi is currently doing better than the last one.
And I didn't spend a penny on oil analysis or synthetic oil, nor do I intend to. Nice try Molafool and Barry Liesome.
Of course, if my owners manual suggested that I should use synthetic oil, I would at a moments notice. But it would only be lubricants that clearly meet my specific vehicle specifications. It's your choice, you decide! If you know more about the vehicle you bought/drive than those who designed and built it, well, . . . we will all wonder why you did that and eagerly await you latest product.
Chumley