(Okay, it may have been a good idea ONCE -- as legend has it, SAAB used this plug to keep simple-minded independent mechanics from mistaking it for the engine-oil drain plug, thus accidentally letting all the lube out and sending the customer off with a dry transaxle. Be that as it may, I distinctly recall finding a similar type of plug in the transmission of a 1.6-liter Ford Capri "back in the day," and it was far less likely that a mechanic would make this mistake on the Capri's utterly conventional front-engine/rear-drive layout. I think it was just something Ford, and Saab, did to make life more difficult for do-it-yourselfers!)