Compression testing !!!
 

How acurate is the dial tester that you can pick up at an auto store? I remember reading somewhere that it can be off by upto 40% ??? Just curious as it gives me a reading of approx 55-60 although I did see it spike once at around 100.

it will not give you a definate by the book reading, it will tell you the relative condition of the seals and the comparativeness is usefull.