I have a 1998 Olds Aurora (220,000 mi) took it to Co., ran just fine, oil changes EVERY 3000 mi using 10/30 Synthetic oil since it had 96,000 mi on it, got to Co.on 2nd day of trip oil pressure dropped to 0 when idling and overheated, decided to rent car for time we were in Co.Drove Aurora back to Il. making sure not to let it idle, ran fine as long as we kept rpms up. Both GM dealer and Cadillac dealers told us would be cheaper to find another engine. So we found one with 56,000 miles on it, had our son change motors, got it home a month ago and its doing the same exact thing!! Any ideas guys??? Oil pressure goes up to 95psi then slowly goes down to 20psi, then up to 95 and down to 20 continuously, down to 0 if I let it idle too long.