Sometime in the '90s, most all upper engine air intake parts, "manifolds", were still metal, with big rubber attachment hoses. General Motors designed and introduced their first all-plastic intake manifolds. By way of explanation, these hunks are attached to the cylinder heads, and convey air and gasoline into the cylinders. Historically, many got too hot, causing the gasoline to vaporize (boil) inside the carburetor, or worse yet, the fuel line conveying the life-blood to the carb. This was infamously called "vapor-lock". It stopped the engine. To help prevent this, the designers mainly routed engine cooling fluid up out of the heads, into the intake manifold supporting the carb., to keep it "cool". Cool still being pretty hot, but it helped. Here comes the quirk: New GM cars and trucks coming in with coolant leaking as though the manifolds were made like sieves. The plastic they used was severely attacked by standard engine coolant, and eaten through by it! Surely, this outrage threw many devout GM customers over to their competition. GM quietly replaced the rotted away manifolds under warranty, replacing the coolant with a new, "improved" type. The new stuff hit the aftermarket amidst worried concern expressed that if your GM product had not yet succumbed, rush out and buy the "new" coolant, and replace the factory-installed stuff. Interestingly, the new stuff was priced about four-times as high as the old traditional Prestone. After that, it became a game of color-identifying coolants, as to whether they were "GM safe". Seems they settled on orange. Prestone is yellow. Crap is brown, which they all were deep down, but everybody was scared. Aftermarket came out with some other color, claiming it was safe and intermixable with all! Prestone quickly countered with a new Prestone II which was universally OK, but very high priced. These high prices have prevailed, never to come down, recession or no. Now, the "biggie": Did GM intentionally mis-engineer the manifolds, to ultimately quadruple the retail price of coolant? Maybe, and especially if they had believed their plastic would last through the warranty period. If it had, and no doubt some did, those owners likely paid blood to dealerships to have manifolds replaced.