that isnt a very good example...

yeah nordic man thats what i did before using the yedropper tool and use a big brush with low opacity so the colour difference is less noticable but ive made layers for the darker part of refs so ill join them together in one big layer so i can redo it in the one shade

i think i know what you mean icandi but in my last wip there i changed the white for a light blue does it look anybetter?

i think when i start adding details into the refs it will be less toony thanks for the comments so far peeps

After looking at your WiPs, I think its better for you to use references first..
Looks like you're using only one color/tone and use the burn/dodge tool for shading. Not very wrong ofcourse, but to achieve realism you should use different colors/tones.
Your chops are looking pretty toony and oversaturated. By using different brushes, pentool and colors/tones it will look less saturated at first and it will also look less toony!

Best way to learn to brush realistic is to start with overbrushing, then using references, then combine using references with your imagination. It is not forbidden to use references and it can only help big times!

The matte black ford looks the most realistic, because you used references and did some overbrushing! This already proves what I said

I see you like blue ;p Try to find references of blue mercedes slk's or blue cars with almost the same shape. for example: http://www.agdesktop.com/wallpapers%5Ccar%5Cmercedes%5Cmercedes_slk350_class%5Cmercedes_slk350_class_025.jpg
or
http://z.about.com/d/cars/1/0/D/O/1/ag_09slk55_frttopdown2.jpg

Best thing to do is to find a bg first.. The refs on the car in the bg could help you by creating a realistic chop.

I'm pretty tired, so there is a possibilty that you dont really understand this all ;p If so, let me know.

Hope this will help (not only for you, but also for everyone else)

i agree with sven