I used Zmax in my car one time and it run cooler; says the guage. Some reviews on the stuff say it causes corrosion. I wonder if these engine did not already have corrosion and the zmax just cleared away the gunk so you can now see it. I mean it can't cause problems because Shelby puts in in his cars all the time and I guess the only way to solve the is which is will zmax hurt your car is to ask him to check for corrosion and see if he has any in his cars. So if you are out there sound off please. Meanwhile what results are yall getting from Zmax and is it a problem or not?