Having the sun directly behind the car means the car is in shaddow and also quite hard to look at. Positioning the car so the sun wasn't in the image, but still having the yellow sky colour would ahve worked better
You picked one of the hardest set up you can imagine. a shot against the sun, with glare, hard to get the WB right. And hard to show details of the car.
There's a lot that's right about this shot, the location, the framing, the strong colour of the background. Where it fails is that the setting sun sitting directly behind the car almost leave the car looking a little washed out.
This shot may have worked with a different coloured car, but with the white it might have been better to wait until the sun had actually set and just shoot it against the orange / red sky.
I bet you're getting a lot of comments about that noise! Some fill flash (on-camera would have even been something) might have made it so you wouldn't have needed to bring up the blacks so much (I assume that's what you did, anyway).
I also think the flare is a bit distracting since it's on the car. If it was just in the sky, I'd say go with it, but not when it's covering what you're selling.
I might have also cleaned the dirt off the back since there's not a lot there : )
I do love the location though. The yellows are the oranges are great--very summery. Fits with the "go anywhere," summer road trip, driving in mud puddles thing : )
As I look at this longer, I think I also might have put the car a bit further to the left to leave some room in front of it.
Composition is off (for me). In general, I think it would have worked better to compose the BMW more to the left, going into the frame vs leaving the frame. I'm sure it was an artistic decision to have the sun directly in the background, but I think it hurts more than helps the image. It creates glare that detracts from the vehicle. But thats just my opinion.