If you're not doing any post work, keep your contrasts in mind. Camera have a hard time contrasting a really dark foreground with a lighter background or vice versa, that's why some of the colors (trees, sky, etc) look washed out. ShellDude made a good point. I never shoot any landscape shots of my car without HDR. Your camera is capable and once you figure it out, you probably won't ever shoot a standing car pic without it. Oh and +1 for a tripod

 

Thanks for the tip on contrast. That makes a lot of sense. If you are interested, here are the pictures that I retook:


http://www.flickr.com/photos/88285471@N02/8082897799/
http://www.flickr.com/photos/88285471@N02/8082894396/
http://www.flickr.com/photos/88285471@N02/8082904525/
http://www.flickr.com/photos/88285471@N02/8082894857/
http://www.flickr.com/photos/88285471@N02/8082882522/

I don't think the lighting was as good the during the second shoot. Your comment about contrast really proves true when I edited these pictures. What are your thoughts on these?

 

Just a couple of hints about taking good shots in the future.
Try and avoid taking photos in strong sunlight (it casts harsh shadows).
Also try and avoid taking photos where things in the background appear to be "growing" out of the roof/bonnet of your car as it spoils the lines of the car (trees, telegraph poles, the bridge support in pic 3 etc).
Another good idea is to turn the front wheels so they're angled towards the camera.
Something else to remember, and you've done this right, is to make sure the car is parked on asphalt, otherwise the picture looks unnatural from the get go.
The best photo so far (imo) would be shot # 4 from the re shoot (apart from the bush sprouting from your roof).

 

Invest in a good circular polarizer. It'll help with the glare and reflection on the car. This is what I have.
A little editing for you.