On average how many KM does a 4 cyl engine last?

If I take good care of it, If your American you can put miles and ill convert it mysef to km, say for an example a Honda civic hatch

200K-300K miles. In most cars the engine lasts longer than the rest of the car as long as the maintenance schedule is followed.

I've had them well over 400,000 km.

Honda… They tend to start burning oil when they get up in age. Same with Toyota. Honestly, as far as engines go, you're better with domestics.

In reality, it's rarely the engine that dies anymore. Even automatic transmissions keep going. More often than not its the rust (again, really bad on Japanese cars compared to American) and all of the convenience features that fail that people don't want to spend the money fixing and don't want to live without… Like power windows, air conditioning, heater core, blower motors, door handles, wiper motors, etc etc etc.

Hi the modern car is designed to do 100k miles or 8 years which ever comes first.

Some could go for 1 million miles (1 609 344 km)

If taken care of, they can last over 1 million miles. I have seen a couple with 600,000 miles and a few with 400,000 miles.

But the way most people drive and maintain their cars, most 4 cylinder engines die around 175,000 miles. If you are talking about the reliable Honda Civic, nearly all of them last well over 200,000 miles. I drove my old Mazda to 165,000 miles, then I sold it. But it still felt and drove like a new engine. I never had an engine problem in that car.

Because of legislation that requires the engine to run clean for a long time, they are constructed much better than years ago. The engine should last until the car isn't driveable any more.