NOTE: To avoid the building of mice nests, and wire chewing, of the wires and areas under the engine tin shrouding--lay some of yer wife's clothes dryer sheets around the engine, and mice and other critters will go some place else to make their nests. Works fer me! Rusty J.

There was no evidence of mice activity. The "dirt" was caked dust. and oily dust.

I will remember the suggestion.

An old sock 1/4 filled with some moth balls or moth crystals, tied in a knot, and draped on the engine or tied to it will also keep mice (and moths) away.
A cat is also pretty effective.

Googeling Finnish baths got me nowhere....

Wrong Finns Tom :^)

I invested in a little 6-gallon, 120psi air compressor. With this I can pump up the tires as needed, and clean off dirt and debris from the mower after using it. Get the longer air nozzle, and you can force a stream of air 'backwards' into the cooling fins after using the mower, which back flushes almost all dirt and debris. Then direct the air into the screen up on top and you can blow out most all the dirt and debris from there too. I have a pasture which often has dry dusty grass, which makes cleaning the fins necessary. I've found using the shop air like this makes the job very fast and easy.

Another area very easy to clean with shop air is the space around the belts and deck pulleys, between the deck and the chassis. Blow that area out after each mower use, and it helps keep the belts and pulleys running cooler.

I know this is drifting a little off topic, but my pasture has a mixture of wet succulent grass, and dry dusty areas. This combination tends to create a buildup of debris under the mower deck, which can harden into an almost adobe-like material that reduces the airflow under the deck, and also can grind the air lift 'wings' off the blades. Lots of folks here have posted about how to keep the underside of the mower deck clean, and the little shop air compressor works here too.

I use a little Cambell and Housefield air chisel, and fitted it with an automobile door trim tool (in the picture below). Feed it with low pressure air (about 40psi), and this little air chisel will softly 'buzz' the plastic blade, such that you can run it along under the deck and all the debris comes off very fast and easy. It's safe because she soft plastic blade won't bite the deck steel.