I have a 2003 Monte pace car,firestone says I have major oil leaks underneath,yet cannot tell me what! the car does not leave any spot or drips anywhere yet the undercarriage is covered in oil? motor has never been apart,? valve cover gaskets? is there a rear main seal? I put a quart of oil in it every three months between oil changes??

 

Rear main and oil pan gasket are pretty common lower leaks.

 

X2...I'd venture to say it's one of those for sure.