I am always amazed how uninformed folks are about their own vehicle when it comes to maintaining it. Why pray/tell would the manufacturer put a label detailing a required part, if it wasn't needed?? I suppose they are just trying to make a profit on a less than $5 item, or maybe they are only trying to fool the owner into spending that $5. Probably the same can be said for all that oil the manual claims the engine needs too! Geez.......lol
The reason this particular type engine NEEDS the sealant is because of the two completely different metals that the block and heads are made from. The Aluminum block and Iron heads have different expansion/contraction rates. When both are at NOT, there isn't much of a problem, it's when they begin to cool off when the problems arise. If/when coolant begins seeping from its 'jacket', it's eventually gonna end up in the oiling system. Coolant and oil don't mix at all. That's the problem! Coolant in the oil system is not a lubricant for the crankshaft/bearings/etc. of the engine. Once the innards of the engine get a taste of coolant, they begin to wear at an astounding rate. That is where the money pit is with an Aluminum block/Iron head engine. A lousy $5 item prevents the problem, but for some crazy reason, folks refuse to believe spending that $5 is a good investment.
This is a Cadillac group, so I would imagine everyone drives a Cadillac. The guys that make the thing say you need to use the stuff, so use it! Unless, of course, _you know more_ than they do.....Happy Motoring!
Dave S(Texas)