Just extended my 2019 base warranty with a 4 year "GM Protection Plan". The forms also offered a "Maintenance Plan". When I asked what this Maintenance Plan includes, the response was "the maintenance plan which covers oil changes, tire rotations, vehicle inspections, cabin, engine and seat filters, brake/clutch hydraulic fluid, transmission fluid, spark plugs, transfer case fluid and draining, flushing and filling of the engine cooling system" and "includes part and labour". What do you people think; good investment?