My car runs a LOT better than I recall it running in a long, long time. Mileage is definitely up on the order of 7% on average, maybe a little better. I'm still getting over 40 mpg on certain runs that I make to Charlotte, NC from my home here in Wytheville, VA. The car used to get only about 36 to 37 mpg on that trip. I calculated 40.2 mpg on one trip during this latest OCI. Not bad for an engine getting ready to turn 200,000 miles. :) I'm not saying this will be typical, but this is what I have experienced with my car.
As Gary rightly pointed out, I have long been a skeptic of any kind of "wonder additive" for motor oil. (Search some of my old posts here). :o :D I have for some time been in the camp that says "everything your engine needs is already in a good off the shelf motor oil." I do still believe that, for the most part... but this AutoRX stuff is in a class by itself.
I don't know the chemistry--I just know it works. I've used kerosene based engine flushes in other vehicles I've owned over the years. I figured they would flush out the sludge, and maybe free up stuck rings... but apparently they weren't doing much--at least not compared to what Auto-RX does.
Let me add this: If you have an old car with a lot of miles on the clock, and it's getting kind of sluggish (and truthfully, you may not even be aware of how sluggish it has gotten, if it's been happening gradually)... an AutoRX treatment will very likely amaze you, and pay for itself in short order by way of improved gas mileage (assuming you have some stuck piston rings, which you probably do have in an older engine)... Even if you don't look under the valve cover, just give it a try and see if I'm not right.
I'm not being paid by anyone to say these things, I assure you. Simply put this is one of those rare oil additive products that actually does do what it says it will do.
Dan
-- Edited by Frank on Sunday 15th of December 2013 06:12:42 PM