The oil light flickered on two occasions today (for the first time) after I applied my brakes. I last changed my oil on 5/23/03. My antifreeze is the Dex-Cool 5 year stuff that I added in April 2003. No leaks were under the car. I changed my oil, found it was black, and only 2 quarts came out (plus whatever little was present in the oil filter). I found no leaks around the oil filter and saw no mixing of coolant and oil. My brick has been problem-free until now (has about 200k miles). What could be causing the two quart loss?

Thanks in advance!