Though flammable rubbing alcohol and lighter fluid. A product shown in the past to remove tar well is WD40.
After taking a dull knife to scrap the excess off, take one of the above chemicals (preferably the WD40) and blot onto the stain. Let it sit a couple of minutes and rub out with a cloth.
You can use hydrogen peroxide to remove pet stains from white carpets. Simply mix peroxide with water and pat onto the stain. This does not work for colored carpets.
get a professional cleaning
stains are on carpets because of people walking on them
solvents remove / breakdown oil stains. I use an orange solvent for removing oil from carpets when cleaning them.
The carbon tetra chloride removes only organic material from cloths as Grease, Wax, oils, tar and hydrocarbons.
Take a cleaner like spray and wash and spray in the spot then a warm wet rag and scrub.
This sounds silly, but if you go to monk.usanetwork.com, there are many tips for removing stains from carpets!
My carpets have several old stains that are hard to remove. What is the best carpet cleaner product on the market?
Hoover Steam Vac is the best steam vacuum for dirty carpets and cleans tough stains.
capet cleaner
with mr.clean magic sponge...
Try Resolve carpet cleaner, that worked to get most all of the stains out of my carpet when i moved.