I currently drive an 87 dakota 4x4 3.9L and was wondering if synthetic oil would be all right to put in on the next oil change. Its ran standard oil it's whole life so i don't know since it is 20 years old if it would be ok. My other question would be this truck is leaking oil and trying to pin point it. If i don't drive this truck it doesn't leak. but when started and after driving, or pretty much whenever the truck is on it leaks. Right behind the carb on the back side of the engine is where I see oil being pumped in intervals from a hose connected to either a pcv valve(i don't really know if thats the pcv valve or not someone told me that could be it) or ? that is what i'm trying to figure out. Any help would be greatly apprecited. On a side note where would be the easiest way to find a dye to put in the oil to really pin point other possible leaks.

 

How many miles on it? Sounds like your oil pressure switch is leaking. The only other things back there is the intake gasket or the valve cover. As far as going to synthetic, Don't do it now. It's too old and will create more leaks.

 

Too late in the game, general rule of thumb is if you've run conventional stick to conventional and if you've run synthetic, stick to synthetic.

It sounds like the oil pressure switch to me as said earlier, easy to change once you can get a good sight on it