I have run regular engine oils for 30+ years and never suffered a oil related failure, the majority of the engines ran well past 200k miles, I would have continued running them well past 200k miles but the bodies were rusting off the frames, once I find something that wont rust off the frame in 200k miles I will try synthetic oils...
Keep in mind their is no magic number or oil when it comes to oil changes, if you drive mostly short trips where the engine does not reach full operating temps for more than 1/2 hr then you need to change your oil more often than if you drive it longer than 1/2 hr, what happens is moisture is drawn into your crank case each time it cools down (unless you live in a desert) longer engine run times helps boil out this moisture so you can go longer between changes...
What works for me, after a oil change look at and smell the new oil, I check my engine oil every time I fill up my gas tank, I look at it and smell it, when it gets dark and has a slight smell of gas I change it this is usually about 2000-3500 miles depending on what type of driving I have been doing, 3500 miles in the winter when humidity is real low, 2000k miles in summer when its real high..
My Tahoe turns about 2k rpm at 70 mph, my motor home turns about 3400 rpms at 70 mph even though my motor home sees all hwy miles and moisture is not a problem do you think I will change it more often than my Tahoe? Sure that extra 1400 revolutions per minute add up...
