Lately I have been getting vehicles in with heavy tar and/or road grime build up, mostly on the lower panels behind the wheels and on the tailgates/hatches. It is a well known fact that mineral spirits, kerosene, WD40, etc will work just fine. My issue is when doing just a basic wash, detar, decontaminate (clay bar), and wax or seal on dark colored vehicles. How are you guys removing tar and road grime build up without damaging the vehicles finish when the customer does not want a polish? I know products like Tarminator, Tar X etc will do this. Are they the only options or is there a more cost effective option?