The best tera type on heatran?

Heatran is the quintessential fire steel trapper in OU. It has a 4x ground weakness that makes it exploitable by the 8 fucking ground types in the tier and tera ground Pokémon like volcarona. It is also a fire type that is 4x weak to ground and neutral to fire instead of resisting fire especially when it runs flame body.

This means it is liable to be set up fodder for volcarona's fiery dance.

To solve this heatran should use tera fire. This removes it's fighting weaknesses and halves dage taken from ground type attacks.

It also means it resists volcarona's fire stab so it doesn't become set up fodder. It also gives tran a adaptibility boost on lava plume which is like scald but fire type so it can try burn tera ground volcarona and landorus therian.

Moreover, it means dragonite is not a safe switch because adaptibility boosted lava plumes can cancel out multiscale and fish for burns that cripple dragonite.

You might wonder what about water types? Well 2x0.5 is 1 which effectively gives heatran tinted lens against water types.

Therefore tera fire heatran is the best tera type for it