Q: Why doesn't anyone offer a quote for a compression or CLT test?

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Why doesn't anyone offer a quote for a compression or CLT test? These two tests alone will definitively tell you if you have a leak or other engine problem and where it is. Why can I not find these tests available at most mechanic shops or sites, including yourmechanic.com

In almost all cases, individuals with engine faults are seeking resolution to an "acute" fault and not so much presenting with a "worn out" engine, that is one with low cylinder compression and cylinder leakage. A compression loss that is large enough to be meaningful, that is one that causes a misfire, or a large cylinder imbalance, will result in a Diagnostic Trouble Code being set. Modern engines are so mechanically reliable that, in the present OBD-II regime, cylinder misfiring (or other engine "malfunctions") are almost always found in causes that stop well short of the kind of serious mechanical faults that cause "low cylinder compression". Of course, in the OBD-II regime, in any given diagnostic if the common causes of cylinder misfiring are not found in the usual ignition or fuel related causes, compression is checked but such is done nowadays using an electronic tool and so, even that check, has become just an integral part of the overall diagnostic. Due to the negligible "added" cost of performing the electronic test, there is no reason to create a separate service, the service that was formerly known as "compression check". To sum it up, there are a confluence of factors that explain the change you have seen: 1) engines are mechanically reliable, so much so that "loss of compression" is really not the issue it once was when a customer presents with a problem; 2) On board diagnostics, and new electronic diagnostic tools, have changed the nature of diagnostic protocols; and 3) if compression testing is needed the test itself is just subsumed within the overall "engine diagnostic" and no need to bill separately. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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