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Dear advisor,

If a used car's compression test result is assessed as good, with minimal differences between cylinders, is the engine therefore not worn out and in good condition? What engine parts would then be considered in good shape?

Thanks.
Leo

An even compression test is a good indicator that the engine is still operating evenly on all cylinders and therefore, components such as the pistons, rings, cylinder bores, valves, valve seats and cylinder head/combustion chamber are all in good order.
A good compression test result is no guarantee that the bottom end (bearing shells, crankshaft etc) is in good condition, however, a good mechanic can form a reasonable view about these parts just by listenning to the engine.
Ultimately, as most major engine components wear at a similar rate, a good compression is a reasonable indication that the engine is OK.

Dear advisor ABayliss,

Thanks very much for your informative and reassuring explanation. I actually visit this website regularly and I'm learning more and more about vehicle-related matters. It's a really excellence service that you and your colleagues provide to the motoring public! Cheers.

Leo

Hello, I recently had an inspection done on a Honda Elysion and the relative compression reading for the four cylinders were 100, 100, 95, 90. Is that 5-10% difference in the last two still considered minimal and basically even?