[MATCHBX]

Because if you buy a used one that is supposedly in decent shape, you have no idea if there may be a problem with any of the seals (orings and such) until you bolt it on and try it. I have never found one that I've pulled apart that the orings weren't completely hardened from age and heat. Plus you also have the added satisfaction that you know what it looks like inside. Plus you have the reassurance that it will last for quite a while.

I mean, would you buy a low milage engine and just stuff it in your car without at least dropping the oilpan to see if it's ok? If you open it up, you might as well refresh the seals while you're in there. I think any engine rebuilder or car mechanic will back me up on this one. If it's used, make sure it's good enough to last for a while before you bolt it to your car.