The optimum Driving speed Depends on what rev range you keep your car at and of course the speed your after but in your case 70 mph at 3000 rpm your Nissan will be very economical at say 65 mph or 2750 rpm it will save you more but only if your travelling more than 100 km or 60 miles. Because its a V6 it probably gets you 22 to 25 miles per gallon and around town 15 to 20. as a rule change gears between 2000 and 2500 rpm. in our country our speed limit is 60 mph so I’d be doing 60 mph=2500 rpm to get max fuel saving.

The government figured out back in the 1970’s that 55 mph was best and set it as the maximum speed limit on all interstates, for a few years. They also found that the accident fatality rate dropped at that speed.

My guess is that the ideal speed for most cars is a little higher now that manufacturers have learned more about building fuel-efficient engines. Trucks should have a lower ideal speed due to higher gearing and RPMs at a given speed.

Well, Richard M, your namesake, Richard M. Nixon, thought 55 was a good compromise during the Arab Oil Embargo in the early 70’s.

The exact answer depends on the vehicle, engine and transmission, so it’s not a cut-and-dried answer.

65mpg

ive always heard 67 interstae and 45-50 rural…i dunno tho