I would call a carpet store, tell them the type of carpeting you have and see what they say. Some things recommended otherwise could possibly change the color, ruin the pile, etc. and even if you don't want to pay for the store to fix it, at least you'll have a better idea of what you can use and not use. Maybe a home building place would also have an idea - they carry SO many things.

I've had great success using BLUEMAGIC Carpet Stain and Spot Lifter (aerosol) on oil and grease stains on light colored carpet. I got it at either Advance Auto Parts or Auto Zone for automobile carpet, and it worked so well, I use it on the house carpet. I have not tried it on tar, but the can says it removes tar along with grease, blood, pet stains, wine & etc.

Thank you. I'm off to the carpet store and Auto Zone to check out what they have.

worst case scenario is you bleach out the carpet and have to replace a section. if you can find the same carpet you can simply cut out the bad spot and rent a seamer to glue in a repair.

My first thought was lighter fluid. It is a great solvent and has no color.

I know this sounds crazy, but have you tried WD-40. I heard about it on the cleaning forum and it is my new best friend, along with Dawn dish detergent, for taking out any type of grease stain.