My first truck was a 95' Ranger. 4-banger. She ran good, but as she started to get older and have 170K+ Miles, she would run a little rough when she was cold. For about a minute after first start in sub-zero temps you could'nt drive it because the engine would stall when you started to turn the steering wheel while backing out of a driveway...Good truck, but I was 16. I drove it hard and raced it.....Don't get me wrong, I changed the oil and maintained it. but I was never affraid to redline it! :winks
I purchased some Z-max. I put it in, it took about 500-600 miles but I sware it made the engine run much better. Now when I would start it at zero degrees in the middle of the night, it would just run. I could drive off right away, although I would always give it 30 seconds to let the oil get a little warm.
Will I run it in my current vehicle? Nope. It's brand new, and i'll sell it before the engine would really benfit from it. But if I was going to keep the car for 150K+ then hell yes I would run Z-Max! :bigthumbsup