My work mule is a black saxo and as an every day car it picks up a lot of stuff which just wont come off with a normal wash or a high grade polish. I dont get the time to clean it every week but yesterday I decided to try remove a lot of the tar picked up below the door trim. So after washing it down I used "Meguiars Ultimate Compound" and it did a great job. It didnt get every last bit off but it removed 95% of the rubbish and gave it a near perfect finish. Good thing about it is there is no prep work like some cutting compounds, just apply it like you would a normal polish and wipe off the same.
Another alternative is Farecla G3 rubbing compound. Not as easy to buy but also very very good. Requires more care and attention when using because it is stronger so check instructions before. I would only recommend using this if you are confident you know what to do as it can easily trash the paint when used incorrectly.
Clearly these are not to be used in place of normal wax/polish but as a once in a while paint or colour restorer they are very good, and if you want to go the hole hog then get yourself a decent clay kit to get a real glass finish. Couple weeks ago i parked my Evo next to another one which had just been clayed and even though mine was polished to the nines I could feel a big difference in the paint between both cars. Well worth the money but perhaps a little OTT for a work mule.
