I just got done today with the 500 mile Auto-Rx treatment in my 98 Ranger. I was impressed about how it didn't change the way it ran during operation, never overheated, no funny sounds etc.. I also felt confident with it as I have heard alot of good reviews about it at bobistheoilguy.com. What mainly impressed me was how it never thinned down my oil to a "water like" state as you would associate with other engine flushes that are solvent based. I drive total 90 miles to college round trip couple times a week. It ran great, oil pressure was smack in the middle of the gauge and even with the A/C on at times, it ran great. I was going to use Amsoil in it but for reasons I wasn't able to get it time. So I went with M1 SuperSyn. Truck runs great and I will calculate my mileage to see what the increase was. Great product and I would recommend to anyone without fear. Thank you -Mike-