Like the oil that lubricates and keeps your engine running (or should), the coolant you choose to help cool that same engine should be chosen wisely. And unless you live in a paradise-like atmosphere, straight water won't cut it for anything street driven. So, just what is the best all-around coolant, if there even is such a thing? First, let's weigh our options: Ethylene glycol versus propylene glycol.

Ethylene glycol (EG) is the good-old yellow antifreeze we're all accustomed to by now-you know, the stuff that can kill your dog, is bad for the environment, and-for those fortunate enough to fall for the marketing ploy-comes conveniently pre-mixed 50-50 with water (for the same price as a full bottle of unmixed antifreeze!). It does just what it's supposed to do when used accordingly-cool an engine-but it's also toxic and non-biodegradable.

Propylene glycol (PG), on the other hand, is more tree-hugger friendly. Typically, this formulation is substantially less toxic, but at the same time, offers nearly the same cooling characteristics as EG-sometimes, even more so. In the case of Amsoil's Antifreeze and Coolant, the company claims consumers can expect to get seven (yes, seven!) years, or 250,000 miles, use just out of one treatment. Furthermore, on top of being compatible with ALL brands of coolant-including DEX-Cool, Sierra, and Zerex-Amsoil Antifreeze and Coolant is also reported to help stop leaks (cause by hairline cracks in welds and seams) due to its ability to adhere to metal.

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