Also, in regards to the ideal speed on the freeway, I think it depends on your car’s RPMs in 5th gear and where it’s most efficient. I’ve heard 2500RPM is a good spot, and at 55-60mph, my RPMs are right at 2500. So if your Accord is at 2500 at 70, that’s probably the sweet spot for fuel efficiency. It’s just a theory, but I think it has some truth to it.

Drive safely

31.35 mpg. It’s better than normal, but not by tons – maybe by .6 – 1 mpg. But I also determined it’s somewhat of a lousy test because there are so many variables. For instance, I had cruise control pegged at exactly 65 for about 95% of the time I was on the freeway; I greatly limited AC on inclines, and I think I may have done a bit more freeway-driving than before. I decided the only way to really run a good test is to stick the car on a track at a constant speed for some X number of miles, and then repeat it at the second speed, with all other conditions being the same.

However, all is not lost. During the test, I was generally a lot calmer driving – but I have to leave fairly early to be able to stick at 65 (sometimes, it’s just not safe to maintain a constant speed). But I was usually able to leave it on CC at 65 my whole freeway time. Second, I think I’m ok driving slower in general. Today on my way to work, where I had my freedom back, I drove only a little over 70, instead of at 80.

However, (and this would be impossible to get and verify, I admit), if you got together a large sample (say 50-100) of 4 or 6 cylinder cars (not trucks) 5 yrs old or newer (which is my assumption), and you followed my driving pattern, speed wouldn’t be a big factor.

But, since it’s impossible to prove me wrong or right, we’ll take my earlier statement and apply it only to me and my car and my driving pattern and let people come to their own conclusions to my statement. I would be interested though to see what others see in mpg improvements by just slowing down a bit on the freeway. I’ll report later when I’m done with my <=65 test.