A not-so-pulchritudinous mind

There was a retired mathematician who was, we'll say, a few clowns short of a circus. His neighbour bought a new car, a landcruiser-type model, which had markings to that effect on the side panel, reading:

4 X 4

(Because, naturally, everyone who sees such vehicles wonders "do all its wheels receive power from the engine simultaneously?" And the answer is there for all to see - yes. Yes, they do.)
On noticing this, the guy did what all self-respecting mathematicians would do; he went into his house, found a knife, and went back to the car, to thoughtfully scratch into the paintwork on each panel, so that it read:

4 X 4 = 16

Pleased with himself, he wandered off.
The owner of the car returned, and, astonished, at the damage, he brought the vehicle to the garage to get it fixed.
A few days later the neighbour spotted the car again, and his wonderful mathematical insight had been ruined; the incomplete calculation was again just screaming out to be corrected. So, considerate guy that he was, he produced his knife and completed it as before, on both sides of the car.

4 X 4 = 16

The owner discovered his car, defiled once more, and was understandably upset. This time, when he took his car to the garage, he explained what had happened, that somebody was messing with him, but since he couldn't know who, he asked them to just paint in the numbers, as they'd been scratched, to avoid it happening again, and at least to do it in a stylish way.

4 X 4 = 16

So, the neighbour saw the car parked again, but now with his wonderful sum painted on it in full. As you can imagine, he was delighted. So, he took out his knife and scratched the paintwork, on both sides, to read:

4 X 4 = 16

Correct!!