Just curious. I had Mobil1 0W-20 in my 2000 Ford Focus at one point. I've also had 5W-20 and 5W-30 and I felt no difference between any of them. no increased gas mileage. Actually the 0W-20 might have felt a BIT smoother. All Motorcraft filters too. I was also running the 0W-20 during summer. That'd probably drive a few people off.