I bought one of those cheap compression testers, and while I have nothing to compare it to, the quality seems quite good, and the readings believeable.
I find that compression gauges can be inaccurate if you compare one to another. A cheap one would be okay to give an idea of what is going on, but if you were a garage and needed to have some accurate readings for proper diagnostics, then spend the money for a good quality one.
the harbor freight compression tester should work just fine..
If you're just going to throw it back on ebay after you're done, you should get the used one, no question. It'll give you more accurate readings and, in theory, you'll get back everything you paid, less shipping.
The knock off is new right now, but once you check your engine with it once, you'll be selling it at a loss as a used tester
Thanks for the replies, yeah I would like accurate results as there isn't anything specfically wrong with the engine at the moment, just want to see where the engine is at at the moment. And radotd that makes complete sense, think I will find myself a decent used one and sell it on when I'm done with it, thanks!