Interstate MPG

i use CC ALL the time... if on fairly flat road. if there is a lot of hills, it sucks because it overcompensates for small decreases in speed. so use CC on flat ground and going down, and use foot for uphill driving. that will help a lot.

also check your tire pressure

 

2005 Prius with 15,000 miles on it. I usually use cruise on interstate. I make a 50 mile run on the interstate about once a month. It is fairly flat with a slight downhill going south and uphill on the return. I set the cruise at a hair over 70 mph and let it go. If the traffic is heavy, I sometimes take it off cruise to go with the flow. My tires are 40 F and 38 R. In the summer, I get about 50 to 51 mpg for the round trip. I can often do better off cruise as I can "play" the ups and downs, but I often find myself straying way off the speed I want so usually go back to cruise.

This winter, I have seen about a 2 mpg hit. I now have snow tires on it (cost me about 1 mpg), winter gas (I think) has hit me a little and colder temps. All this has cut me to 49-50 for the round trip. I will soon go back to the OEM tires (same pressure) and expect summer gas to come back.

Check your tire pressure. Take it easy on heat/air.

As a side, the only time I have seen 30 mpg was shortly after filling up the tank and I have less than 20 miles on the odometer, depending what I did immediately after leaving the gas station.

Now, when I take my pickup down the highway, I am always wondering what my mpg is. When asked what mileage I get out of it, in the past I just quoted what the sticker said. I only actually checked on it when taking it on a long trip so I could get a good average fuel consumption (a couple or more tank loads to average things out). I would have been estatic if I could have gotten 30 mpg out of that beast! Too bad all cars aren't required to have a fuel consumption calculator/indicator.