When you're in college, you learn how to pinch pennies. I live about 90 miles from my university, the whole trip going along a northish-southish interstate. About 4 years ago, the state raised the posted speed limit to 70 mph. I used to drive about 75, 80 on this stretch, until it rained heavily one night and I did 60 the whole way. I went up from about 28 miles to the gallon to around 32. When I started going 10 miles under the limit in favorable conditions, I got about 36-37.
There is absolutely nothing illegal about going 60 on a 70. I've been doing this in a Honda Del Sol, one of the most diminutive cars on the road. So far I haven't been rear ended. Most drivers, especially truckers, see my rate and react accordingly. As long as I stay in the right lane, I'm not holding anyone up or harming traffic flow.
And frankly, if you get pissed off for having to react to my slow moving vehicle, I'll get a rise out of your irritation and keep on doing what I'm doing. Especially if you're driving a huge SUV or a BMW.