Since you had to fill up the radiator, you may have a leak. Keep a close eye on the coolant level. If it drops quickly, then you probably have a leak.

 

Thanks, Changed the thermostat and the overheating problem is gone. I am on 100% water but will have it flushed and will have the recommended coolant. I believe my radiator is clogged, the flow of water is very low and although the car doesn't overheat anymore, the radiator hoses get very very hot and become pressurized after 20 minutes on the freeway. It is almost hard to squeeze but its very easy when its cool.

 

Anti-freeze not only lowers the freezing temperature, but it also raises the boiling temperature. Along with corrosion protection. I wouldn't go for more than an hour or 2 without the corrosion inhibitors.