if vehicle did "Excellent" on an emissions test, does that mean engine is probably in good shape?

To me, it means that the engine runs well and within the normal range of what is expected. It also tells me that the emission controls and everything else should be doing well.

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Yes. Cars can be in good shape and still fail the emissions test but, at least in Texas, the test is pretty good. If there is a problem it will probably find it. There are mechanical things that could be wrong that might won't register. Something like a clutch going out. The engine though will tell most any secret to the inspectors computer.

As a heavy line mechanic and smog tech for 20+ years, when your told that your emission levels were "excellent", that means at this time your engine is tuned correctly and that your getting real good gas mileage. Is the engine in good shape? Yes, at this time. I assume you do all the regular required maintenance, including the oil changes, and as long as you do so the engine will last. Now lets turn to the ofter forgotten parts of the drive train, your transmission and rear diff( if you have a rear wheel drive car or truck), have you paid as much attention to it as you have the motor. A good running engine is worthless if the trans wont move the car, so I suggest if your trans hasn't been serviced lately, go do it NOW!,

I recently took my 40 yearold Beetle for its test in Spain, its not been run for ten years but the engine has only done16000 miles. It failed on the emissions ,he said it should be 4 and it was 6, whatever that means. I changed the fuel for new 98 octane, cleaned the system , nothing in it, Checked the ignition, points dwell etc, nothing wrong. 4 new sparkplugs .

Took it back for retest and it read 3 so we´re happy .

Very much so, I've been doing emission repairs for 30 years and the single best indicator of an easy pass is good engine condition.

Not really, it just means there's no idle issues with the car. My old car was sitting for 2 years and one day I took it to get the emissions done, and mind you it was still due for an oil change, tune up, etc. and it still passed emissions, and from what I know, the car leaks coolant and oil. so no it really doesn't. but if you want my advice, any car will last so long as you maintain it.

It means all cylinder are firing, and all emission controls are working within limits. Your engine could be leaking oil and anti-freeze, and knocking noise.

80% YES