Some lawn mowers such as the Craftsman 37705 have a washout feature. It is essentially a garden hose fitting on top of the circular blade cover. This allows you to pump water into the blade assembly while running the engine. That action is designed to flush dirt and grass debris right out.
Your Best Digs rated the Greenworks 22502 as the best electric lawn mower. The reviewer found this push mower easy to maneuver thanks to its lightweight design. He also liked that it was much quieter than the gas mowers he tested. However he noted that dumping the clipping was awkward since there was a crossbar in the way and he would have preferred it if the mower came with an extension cord. Greenworks offers the option of buying the mower with an extension cord for $30 extra.
The reviewer at The Wirecutter said This Honda is in a class of its own. He was impressed with how the mower cut grass into smaller pieces with its double-blade design. And he found the Versamow system incredibly helpful. However the reviewer that it was tedious to adjust each wheel when he wanted to change the cutting height.