I think what he meant is 'low engine compression'.
Yes, old engines loose compression overtime due to number of reasons like worn out pistons and piston rings, leaking gaskets, worn out valves to name a few but...
I don't think 170,000km is an alarmingly high mileage as Honda Cities clock well over 200,000 kilometers with ease.
If your car is emitting smoke (Either light brown or thick black) and the engine is making weird knocking noises, burning spark plugs and doesn't feel as powerful as it did years ago then the engine is definitely in need of a top-end rebuild (Tune-up won't do anything) which costs a LOT of money and is usually not worth it because its usually better and cheaper to replace the car.
And if your cars show none of the aforementioned symptoms then the mechanics might not being completely honest with you.
In any case; here's a visual guide on how to check engine compression. It's very simple and only takes about 30 minutes or so. It's easy enough for you to do it yourself; but you can also get it done by a mechanic in your close supervision:
And while you're at it; might as well 'read' your spark plugs too. Here's a link:
You can tell a LOT of things about an engine just by looking at spark plugs that have been in use for a few weeks.
YouTube is full of these DIY videos and guides; so watch a couple of them to get yourself familiarized with the general principle behind it before proceeding.
Best of luck.
