I moved into a new home during the summer and was pleasantly surprised how the Prius liked the extra time on the interstate. My round trip is 33.5 miles now to work compared to 16 miles before I moved. My old in town mileage was 48-51 with hills in summer or winter. Now I'm getting an average of 54-56 mpg on a mostly level interstate highway. Tail winds have been a blessing and going home the other day I was a little over 70 mpg for a short time and driving to work against a southern wind and a little faster driving reduced the mileage down to 62 mpg. This car is crazy....
Warmer weather - Check Favorable winds - Check Flat terrain - Check Longer commute to reduce engine warm up penalty - Check Michelin Energy Saver Tires - Check I imagine you could do even better if you could reduce your top speed a bit. What is your cruising speed? I'm going to guess 65+ mph. Are your values the computer displayed or hand calculated?
Codyroo, your right, 64-65 mph. One thing that I noticed was average speed, 51-52 which surprised me. Hand calculated at the pump and usually 1.5 - 2 mpg subtracted from a higher reading on the computer display.
An average speed of 51 - 52 tells me that you have lots of highway commuting and almost no slow traffic during your commute. Just the normal surface streets (1 - 2 miles) to the highway and (1 - 2 miles) from the highway to your house. You could probably eek out another 3 mpg or so if you inflated your tires to max psi (~1 mpg) and slowed down to 61-62 mph (~2 mpg). But even if you don't do either of those things, you are doing extremely well with your car!
Flat roads and temps in the 70s (meaning no need for A/C), with mainly interstate travel, will make for great mileage in the Prius. In mine, which has 17" wheels, I figured about 60 for 60, meaning 60 MPG when driving 60 mph. Going up to 65 dropped FE to 55 MPG, while dropping the speed to 55 mph increased the FE to 65 MPG. And this is without doing anything but driving -- no attempts to hypermile -- and usually running on cruise control. In a non-Model V (Five), you should get even better mileage. Things that will kill your FE: speed, underinflated tires, rain, poor road conditions (sticky asphalt in particular) and using your brakes on the interstate.
Winds affect FE so much more than people realize. Traveling pretty much the same speed on a recent road trip I had a strong head wind (low 50's mpg) on the way there and a strong tail wind (70ish mpg) on the way back.
Something else.... I have a couple of small mountains near the new house I travel over that are a quick climb up and a slow downhill for about the first few miles before the interstate (an unexpected perk?). I get a great charge up on the battery coming and going and only drop a few tenths on the climb (depending on traffic).
