I put Auto-RX in my Dad's 98 4.3L Blazer with around 150K on the odometer. Well, pretty much all the 1500 miles of the cleaning phase were 75 mph highway, which helped a lot. So, mileage on the trip computer is up at least 2 mpg, power is AMAZINGLY better. My Dad and I just about crapped ourselves driving up to our cabin in the CO mountains. Normally on some of the passes, it's dropping down into second and just pinging/bogging like a mother. Now, it just sailed up Wilkerson Pass in 3rd gear with night and day better power. Also, Idle is much smoother, and the engine is whisper quiet. My Dad is freakin' out about how much better it runs. It also seems to have slightly higher oil pressure. One thing I also noticed: the oil return ports from the top of the heads had to have been partially blocked. Before the treatment, I'd have to add around 5.25 quarts in a 4.5 quart system to get full on the dipstick. I did that with the rinse oil change, and after about 200 miles, the oil was at least .75 quarts overfilled. It never did that before, except you'd top off like 1/2 quart, then pull the dipstick, and it would be 1/2 quart overfilled, so it had to have been the oil return ports being clogged. It also seems that the benefits become more noticeable AFTER installing the rinse oil, and that also when the oil level mystery cleared up.

Drew99GT