This is a Green MTG commander that does everything, a value engine that provides self-mill, lets you grab lands from the graveyard, and makes nasty big elementals
This spell never goes worse than mana-neutral, and it often trades up in mana
It's quite balanced for a tribal deck, but that doesn't take away from its inherently aggressive nature
Rather than playing the Speedway for free when you play Jim, you want to put the Speedway into play after Jim is on the board and at a location
If you can combo off, this will work much like Raptor Hatchling, giving you the win if your opponents don't have an answer
Related: New CMM cards and Planeswalker Party Precon decklist Every new card in CMM Eldrazi Unbound Precon deck There are 10 new MTG cards in the Commander Masters Eldrazi Precon deck