The "Imperial gallon" is not the US gallon. One Imperial gallon = 4.546 liters or 1.20 US gallons.

The 71mpg (Imperial) is really 59.16mpg (US)

 

Too true. She's been coming around though....on our last trip, I told her she should pay attention (without distracting!) to the mpg display so she can see what type of driving gets optimum FE. She has modified her driving a bit...but she hates going less than 70 on the freeway.

 

I agree with you

On longer trips, I don't feel the gas savings are nearly with the extra time to drive extra slow. The difference between 55mph and 75mph in my car is about $4.00 per extra hour on the road. (Note: this cost/benefit only applies if your top speed is not fast enough to risk getting a ticket, and on longer trips)

Trying to minimize speed changes, driving with load over hills, coasting more etc. still saves a lot of fuel compared to driving erratically at the same average speed.

My philosophy is to go with the ambient speed on the road in the middle lanes. If by driving extra slow to try to get the very best gas mileage I cause countless drivers to brake, change lanes, and overtake me, doing so actually increases the amount of pollution in the atmsophere by hurting the fuel economy of all those other drivers who must accelerate their own much heavier vehicles to pass me.* The same applies when accelerating from a stop at light that has just turned green. Often accelerating more slowly would be economical, but doing so could cause a whole line of cars behind me that are already up to speedd to have to brake then re-accelerate. By accelerating rapidly, those drivers behind me can maintain their momentum -- saving far more fuel than I give up in the maneuver.

*Note: I'm not suggesting that those on the forums who hypermile to conserve fuel are inconsiderate, if done without obstructing traffic flow, there's absolutely nothing wrong with hypermiling. However, I do see drivers out on the road (usually on the phone) who fit this description.

 

My philosophy is IFT (I Follow Trucks). On most of the Interstates in my neck of the woods, the 18 wheelers are limited to 65 mph, the ideal cross country speed for my NHW11, 03 Prius. I don't 'draft', that is too fatiguing. Rather, I follow at a comfortable distance and get to where I'm going at a nice pace. There is enough space to deal with road debre and drivers coming up behind me just assume I'm part of the truck. With XM radio, it is an easy way to make a lot of non-stressful miles.

Even in those states where 18 wheelers can go 70+ mph, it is fairly easy to find a truck company whose driving policy is 65 mph. In short, don't worry, be happy.

Bob Wilson

 

I find 65mpg to be an optimum speed for freeway driving with the Prius. In those cases where there are lots of hills, you make up for losses on the uphill with a coast downhill. Its not difficult to get 50mph in the Prius this way. But on some freeways, it just seems really difficult....probably because the uphill grade is nearly imperceptible, and you get less benefit when coasting..........in those cases I just set the cruise control to 65 and forget it. My average in these cases has been around 45mpg as long as there are no significant cross winds.

 

i live in a flat area -which is most of florida. Its very difficult to 'coast around' this way so our MPG is really only going to get towards EPA . Some guys live in hilly areas where they can coast a lot -doubling their mpg from their trip up the hill.

cheers