I raced my fd for the first time this weekend after I just finished breaking in my rebuilt engine. After about 15 miles (6 miles at a time) of all out racing my engine started smoking and I got black flagged. The engine was leaking oil and down about a half quart since the start of the race. Couldn't tell where the leak was coming from but it looked like the rear main seal. Also the oil on the dipstick was dark brown after a recent oil change. Is it normal for the oil to turn brown after 15 miles of racing? Mechanic seems to think it may be a problem with the oil pump and seals.