Boosting this. Numerically the chainsaw looks like it should be the be-all-end-all tree eater, but judging by what I see in game, it's as if the system is doing the maintenance check too often.

For other new people finding this, & Since its never going to get fixed;
workshop\content\108600\2335368829\mods\Authentic Z - Current\media\scripts\AuthenticZ_item_Chainsaw.txt

ConditionLowerChanceOneIn = 250
ConditionMax = 25,

FuelConsumption = 0.1,

Seemed to be alot better