Compression tester VS Leak down tester, Which one to buy? Options

[UVZ164]

Hey guys,

Looking at expanding my tool collection with either one of these two.
The leak down test provides more comprehensive results as to where leaks are and exact percentages of cylinder leakage.
But the compression test results seem to be what everyone uses in terms of a PSI number.

My question is if i use the theoretical value of compression provided by the BGB which is 178 PSI (5s-fe engine) and i use the leak down tester and get a cylinder leakage of 10% can i just deduct 10% from that 178 PSI and get 160.2 PSI compression?

If that way works i guess ill get the leak down test if not i need some opinions on what to get.

Thanks,

Reece

[Syaoran]

Compression testers are cheaper than Leakdown testers.

You should get a leakdown tester, since it will tell you exactly what is wrong.

Compression testers are all different, and one may read 170psi and the other 180psi. All you need to know from a compression tester is that all values are within a certain range of each other (+/- 5% IIRC), not a specific value.