Dealing with Tar Spots on your Paintwork
You will need to purchase a good quality bug and tar remover such as Gold Class Bug and Tar Remover from Meguiar's. You will also need a microfibre cloth to remove the excess product afterwards.
Simply locate the affected areas and apply the bug and tar remover with the spray applicator. Leave to soak in for a few seconds then agitate with the Microfibre cloth.
Wipe the residue off with the other side of the microfibre cloth and examine again.
If the problem still persists you could try using the reverse side of your wash mit which should have a bug remover. Then repeat the above process.
Now we can look at cleaning the glass surfaces on your car.