Off-topic, but what the hell...

The car is capable of more. My guess is that you're still not doing it right (no offense). Old habits are really, really hard to break! Cruising from Naples to Tampa on I-275 where the average speed is about 80 mph and people are constantly passing you at 85-90... VERY difficult place to try to get good fuel mileage. You may feel like you're babying it compared to how you're used to driving, but you're probably still driving 75-80, and the real killer is that it's hard to maintain a constant speed on the stretch of road. You're always slowing down for traffic, speeding up to get past it, etc.

If we're talking about a new Sentra, it probably has an in-dash computer that will give you an MPG readout, right? Try resetting that readout when you start each trip. You'll begin your trip with really shitty mileage... like something under 10 when you pull out of the driveway. But, as you drive, the engine warms up, and you travel a few miles, you average out the cold-start and you'll get up to 30 pretty easily. From there, start working on it. Do everything you can to get that number to increase. You'll learn what works and what doesn't.

Learning to use DFCO is easy... what's hard (especially if you're used to driving fast cars) is learning to have a REALLY light foot on acceleration. Making that adjustment from 60-70 mph on the highway... there's potential to save a lot of fuel by always doing that with a super-light foot rather than making it happen "right now" like you know you can.

If your car has a real-time instantaneous MPG display, that's even better for "training". It'll show you exactly what I'm telling you. Light foot = 25+ mpg on accel. Heavy foot = 12-15 mpg on accel. It all factors into your average MPG.