http://www.bimmerfest.com/forums/sho...ting+for+fools
http://www.m5board.com/vbulletin/e60...e-our-m5s.html
http://www.carbibles.com/engineoil_bible.html
http://www.carjunky.com/news/motor_oil/mom4.shtml
Draw your own conclusions but we used to change oil every 3000 miles I don't feel good letting it go over 5 k
There are combustion byproduct build ups and the additives are used up the oil becomes
acidic and you are recirculating this stuff through your motor. This is extra true for turbo cars where the oil runs much hotter.
Oil changes are not a big money making operation