Easy Answer: If you accept the high end of the government's oil spill estimates, BP is now the largest spill in the Gulf.
But it's not the largest spill ever, not yet.
If you take the high end of the government's oil spill estimates, today's the day that the BP oil spill became the largest ever in the Gulf of Mexico. According to the Associated Press, 140.6 million gallons of oil have poured into the ocean since the BP blow out.
That tops the previous Gulf of Mexico record holder--the Ixtoc I, which spilled 140 million gallons off the coast of Mexico. That well was being drilled by a platform on lease to Petroleos Mexicanos (PEMEX).
But in 1991, during the Persian Gulf war, Iraqi forces dumped between 252 and 336 million gallons of oil into the Persian Gulf.
According to PBS, worst case estimates for the BP spill have it spewing into the ocean at a rate of 4.2 million gallons a day. At that rate, the BP spill could be as large as 280 million gallons so far--bringing it into record range.