Hi Sarah
Euculyptus Oil (tiny bottle from chemist).
Amazing at getting out Tar, grease and oil from almost all fabrics, carpets included.
Put small amount on cotton wool and rub into carpet (dries very quickly), apply 2nd application if necessary.
The added bonus is you'll have a clear head - its a strong solution!!
Have used this remedy many times, on clothes and carpets. Got a large area of tar out from a friend's carpet once (cream), but she was doubtful at the time in case I was gonna make it worse. Had to have the windows wide open for a week to get the smell out!!