I recently changed the oil in my '82 300D Turbo and added a product called "Engine Restore". It comes in a silver cylinder for either 4, 6, or 8 cyl applications. I have noticed a bit more pep with the 303,000 mile engine. This product is priced fairly reasonably, under $10.00. Has anyone else had a good experience with this or any other additive?

I am also looking to add a Pro-Long tranny additive, but I've heard stories of the transmission going out after adding stuff like that.