Pokemon Platinum: Is My Torterra moveset good?

It has Crunch, Earthquake, Grass Knot, and Giga Drain. My Torterra is Lv 51. If you don't think a move is good for my Pokemon, then list some other moves I could teach it and why they are better than the move you don't like. Im a little scared that Earthquake might faint an Ally pokemon during a double battle. That is my only concern about it. I used to have Razor Leaf, but it sometimes was a little weak so I swirched it for Earthquake.