I know they're called oil-burners... but we've got a sizable amount of blue smoke puffing out the tailpipe. It does not happen at idle, rarely happens when taking off, but usually when cruising or letting off the accelerator. At the suggestion of a mechanic who pointed to the valve seals, I poured in a bottle of ATP-205 oil seal conditioner. Any experience with this stuff? How long is it supposed to take to work?

I see that valve seals appear to be available, but piston rings do not. Any suggestions which is more likely to be at fault? Where could I get rings?

This is an 83 Dodge Ram 50 Sport, 4x4 manual that we're considering buying (for $1800 or so). Apart from the burning and some electrical gremlins, it's a running, driving truck that on paper is exactly what we need. Not a lot of little diesel 4x4's on this side of the pond, so generally, I'm willing to put in extra work to make it run at 100%. I'd just like a better idea of what and how much work that's going to be...