I will try using zippo lighter fluid & let you know the results(probably with pics.)i did not want to use diesel but i am reading lighter fluid is a less harsher way to go.
and applying wax to get rid of the tar is a very BAD BAD BAD idea,before we apply wax you use a detailer spray along with clay bar(professional method) or use the diesel/lighter fluid method.
If you have the carnabua wax, apply on the parts where you find the tar marks, these are not only tar marks, these are oil deposits also. Apply wax in circular motion with the sponge a thin layer, let it dry, it will form a haze. Now there is some physical effort required, use a soft cloth .