Exhaust Smoke: Causes and Solutions

Hello,

I just experienced a rather unusual incident with my Polo, manufactured in 1992, with a 1W engine (1.4 liters, 48 horsepower, naturally aspirated, with 172,000 km on the odometer), which is causing me some concern.

I was diligently overtaking on a multi-lane federal highway, and the speedometer showed 150 km/h in 5th gear, which is roughly just below the maximum engine speed.

As I looked in the rearview mirror, I saw that I was trailing a very large, thick, almost opaque cloud of smoke, colored a medium gray. I was, of course, startled and immediately took my foot off the gas. Just as suddenly, the smoke stopped.

After that, I rode another approximately 20 kilometers to get home, but with a more moderate driving style. The engine didn't have any problems, and it didn't smoke anymore.

Here are a few facts about the matter:

- The duration of the smoke development was likely around 30-60 seconds, until I turned off the gas.
- The engine was definitely at operating temperature (it had already been running for 30km).
- There was enough water in the tank, and the water temperature remained consistently around 80-85 degrees Celsius throughout the process, and it didn't increase even after the event.
- There's also enough oil in it, maybe even a little too much (but really, just a tiny bit).
- The engine is running perfectly fine. The performance, throttle response, and sounds are all completely normal, as always.
- The engine has always been an oil burner, especially when driven at high RPMs. If driven consistently at moderate RPMs, the engine consumes a maximum of 0.2 - 0.3 liters per 1000 km. However, with more aggressive driving, it can easily consume 1 liter per 1000 km.

Does anyone have any idea what that might have been? Any tips on what signs to look for, or what to search for?

I absolutely need the box for my daily commute to school/work, and furthermore, I have two longer trips planned for this weekend and early September, and I would really prefer not to get stranded somewhere with engine trouble.