I bought an 2K1 I 30 with 27K miles on it. I tried Auto RX even though the engine looked pristine. I didn't notice anything at all through the cleaning phase. During the first rinse phase I noticed the oil turning a light reddish brown. I had the rinse oil drained at 2000 miles. It was filthy! Looked like it had been in a diesel for a long OCI. Used Chevron 5W30 with a Wix filter for the rinse, now have Quaker State 10W30 dino for the second rinse with a Wix. The Acura (Trooper) has only 840 miles on its first rinse of Chevron 10W30/Wix. Fuel economy seems better on Acura no change in I 30.