Sadly the fire effects are not very satisfying.
If you look at this:
You can see that the fire effects basically are made out of cyrcle formed textures.
Also the flames are coming out of the middle of the wreck.
in reality they would be all spread over the vehicle.
Here you can see how fire is done really well.
I am sure BIS is able to achieve sth like this too!
The main problem seems to be the flames texture and the the form of the textures. There could be made much improvements with alpha masks and proper positioning of the flames and smoke.
Also a redesign of the smoke textures seems to be important too.
As allways I am glad to help! So if you give me a way to mix them up myself I am pretty sure I can deliver you a good example