I have a 93 buick with a chevy tbi 5.7. 72,000 miles on her. The previous owner has not taking great care of her as far as sevice went. He took great care of the cab and paint, car looks great.I have put the last 25,000 on her. In that time I have changed all the fluids multiple times all syn, changed all hoses and vacuum lines, egr, pcv every 10,000 to 12,000,fuel ,rear end with Mobil 1 syn, trans suck out 3 1/2 qt every 10,000 first mobil 1 now maxlife atf, a complete tune up. Car mech runs great, very strong. I was currently run maxlife syn 10-30 and a k&n oil filter, car holds 4 and 1/2 qt. I was going to do 5,000-suck out 4qts-5,000-suck out 4qts-5,000 then change oil and filter. Or 6,000 suckout 4 qts then 6,000 more then change oil and filter. With maxlife syn of mobil 1 high mileage when my maxlife syn stash dries up, with a k&n or mobil 1 filter. Do you guys feel that one of these is safe? And which idea do you like better? Thank you in advance!!