I have one car that hasn't had the oil changed in 13 months, but I've only driven it 900 miles. One trip last summer of about 500 miles and a few times since then about 50-75 miles each time. The car has been sitting since last December. Oil is 5W30 Mobil-1 Car is a stock Mustang LX-5.0L with 80K miles. Of course the oil looks just like it did whan I put in in last year. Do I change it now or drive it a while? Opinions??