Dear Tom and Ray:
I have a 1996 Jeep Grand Cherokee and live in the hot, dry Southwest. Both my main seal and my transfer-case seal are slowly leaking. There are a number of additive products available at the auto-parts store that claim they will soften old seals and stop leaks. Do any of these additives really work, and can they do more harm than good? -- Holt
TOM: No, they won't do more harm than good. But there's at least a 90 percent chance they'll do nothing.
RAY: We consider these "products of last resort." If you're facing a major engine or transmission repair, then why not try an $8 bottle of Miracle Whip or whatever they call it? On the off chance that it helps, you might buy yourself some more time. Sometimes, that's all you want -- just enough time to finish grad school, or get through your latest divorce or your youngest kid's last seven years of college.
TOM: The products that soften seals certainly won't do any harm to the gears or to any other internal components, so don't worry about making anything worse. And once in a while, we've seen them work for weeks, months or even years.
RAY: So it's worth a try in your case, Holt. After all, if you're looking at spending $2,000 in repairs, what's the harm in making it $2,008?