Most major oil leaks come from the vehicle's rear main seal, which can be expensive to replace. Bar's Leaks® Rear Main Seal Repair is the first off-the-shelf solution to stop both major and minor oil leaks, including rear main seal leaks. It restores seal size, flexibility and elasticity. Chemical polymers fill in gaps and grooves caused by normal engine wear that can continue to leak even if the rear main seal itself has been replaced.