what is the best level to evolve growlithe in pokemon heartgold?

Though everyone else has probably the same answer, I recommend Growlithe evolving at level 48-49. It learns all the possible moves it can (without TMS/HMS) and at 48/49 Growlithe learns a powerful move called Flare Blitz, which has a overwhelming power of 120. Evolving Growlithe early can sometimes be a bit negative, since Arcanine only really learns Extreme Speed at level 39 which has a power of only 80 (besides its basic moves, which I am not sure it can learn after evolution unless you exchange heart scales with that move tutor in Blackthorn City). Though it will take a lot of patience and effort to get to Arcanine (trust me, I'm still doing it), it will be worth the wait with such a supreme move set and stats. And besides, when you're tired of training it and have some cash to spend, you can always leave your Growlithe at the day care and let the people do the rest of your work.

If you can't be bothered leveling your Arcanine and you just want your Arcanine now (which is my favourite Pokemon), level it at 20-25. That way its stats are more developed and it will learn Extreme Speed in a matter of a few levels.

Hope this helped you make a decision you're happy with 🙂

It depends. If you want to focus on Arcanine's special attack stat, I'd give Growlithe the fire stone after it levels up to level 34 (it learns flamethrower at that level).

If you want to focus on Arcanine's more powerful main attack stat (physical), I'd wait until after Growlithe levels up to level 48, to evolve it to an Arcanine.

Growlithe learns a very powerful physical fire attack called Flare Blitz at level 48. After that, I'd evolve it into an Arcanine... And go to the move rememberer (in blackthorn city?), and re-teach Arcanine Extreme Speed (basically a stronger version of quick attack). I think you'll need to give the move rememberer a heart scale for each level up move you want your pokemon to remember back.

Extreme Speed and Flare Blitz are really good physical moves for Arcanine. You get a strong speedy priority move with Extreme Speed and a very strong physical FIRE Same Attack type Bonus (STAB) with Flare blitz.

P.S. Reteaching Arcanine, "thunder fang" through the move rememberer is great too. It's a physical lightning attack that can help you out against water and flying type pokemon! Crunch is also good (Growlithe learns Crunch at level 42).

P.S.S. Just note that... Once you evolve your Growlithe to an Arcanine and go to the Move Rememberer to learn back a move, you can't remember back any moves Growlithe would have known through level up anymore, that Arcanine can't learn through level up. So trying to make Arcanine remember flamethrower from his former growlithe form (at level 34), if you accidentally deleted that move from your move list-- it won't work. This holds true for all stone evolved pokemon also. Also note that you can't re-remember TMs and HMs, if you deleted them from your moveset via move-rememberer! (:

Good luck! (:

Evolve it at 98 to be awesome.

48-49. So it will learn flamethower and extremespeed.

whenever works so long as your okay with using tm's and move tutor

i did mine at level 6. and it worked out pretty well