 2004 2.5 automatic bought 2/2004; 106,000 99% hgwy miles; excellent maintenance; 1 driver only.  Within six months of purchase, 1 piston not firing fixed under warranty--told I was LUCKY!); replaced serpentine belt (3 yrs); hesitating 4 1/2 yrs ($1500. to fix); now, oil leaking into engine, told I need a NEW ENGINE!  My 3rd Altima, other two (standard, 95 & 98, no problems at all. THIS CAR A MAJOR DISAPPOINTMENT. 