1997 Pontiac Transport Antifreeze

The engine temperature is not related to the mixture of water and antifreeze. Leak stoppers don't make the engine run cooler either. What can happen is if the cooling system is marginal to start with, running straight water can reduce some causes of running hot because water holds more BTUs of heat than antifreeze does. If circulation is poor, the higher concentration of water will move the heat from the engine to the radiator faster.

What you will lose besides the obvious freeze protection is the water pump lubricant and corrosion inhibitors found in antifreeze. Acids build up in the coolant from the normal seepage of combustion gases into it. The antifreeze is alcohol and always will be, but we replace it every two years because that's when those additives wear out. GM has a lot more trouble with corroded and leaking heater cores than anyone else, especially on those vehicles that use Dex-Cool, (Dex-Mud). You'll be promoting that corrosion if you don't have antifreeze in the system.

210 is fine. 150 is very bad and will lead to excessive engine wear, assuming it's correct. Feel the upper radiator hose after driving on the highway. It should be too hot to hold onto for very long. If it is, your gauge is not reading correctly. If the hose is cool the thermostat is sticking open.

Engine parts, pistons in particular, are machined to fit perfectly when they expand from normal engine temperatures. That's why 99 percent of engine wear takes place while the engine is warming up, and very little wear takes place on long highway-speed drives.

We like to get Dex-Cool out whenever possible. GM advertised it as "lifetime" coolant to trick people. It made their cost of maintenance look lower than for their competitors and they advertised that. Then, once you bought the vehicle, it says right on the coolant reservoir to replace the coolant every three years. That's because the additives wear out. Those are water pump lubricant and corrosion inhibitors. Even the Dex-Cool manufacturer recommends replacing it every two years, not every three. GM already has a lot of trouble with corroded heater cores and radiators so you don't want to do anything to provoke that. Use a regular name brand antifreeze but be sure to flush all the old stuff out first. The two are not compatible and should not be mixed.

I was a tv / vcr repairman for 40 years, mostly part-time, and a mechanic for 16 of those years, then I taught in a community college for 9 years. My specialty areas are Electrical, Suspension and Alignment, Brakes, and Engine Repair, but the Dex-Cool information comes from a very high-level trainer who puts on monthly classes for Carquest. He owns a shop near Chicago that specializes in diagnosing the one out of a hundred cars that no one else can figure out, then they turn their findings into classroom material. He networks with other trainers all over the country and they have contacts at many of the manufacturers. Those classes are quite expensive but it's one way mechanics at independent repair shops stay current on the new cars.