Quote: “So far noone has shown the optimum speed with any scientific basis to support it.” Unquote
Peter Noone was the lead singer for Herman’s Hermits.
The real answer to the OP’s question is no one knows.
And if the model being tested is not one equipped with “todays timed pulse fuel injection”?
I guess if the OP has such a car he could just watch the display and see, well there is your answer OP,just look at the mpg readout in you “car of today” you will have an answer down to the very last atom of fuel used.
Are you sure about the fact that your trans does not shift into 5th gear until 50-55 mph?
My car has a 5-speed automatic, and if I am driving at a steady speed on a level roadway, it shifts into 5th at 42 mph. On the other hand, if I really “goose it” to accelerate onto an Interstate highway, it doesn’t shift into 5th until I get to around 78 mph. Much has to do with whether you are driving at a steady speed or you are accelerating.
A consistent speed is one thing…But I think more important is the speed you drive GETTING to the optimum speed. Slow steady acceleration is far more fuel efficient then speeding up and then coasting.
You beat me to it, CSA. I was going to say 0 MPH would save you the most fuel.
The next most fuel efficient speed would have to be the speed the car travels at idle in the lowest gear.
Since we are talking about driving on public roads, I think safety should trump fuel economy, and people should drive no slower than 10 MPH under the speed limit once at cruising speed. If we are talking about interstates, the minimum legal speed is often posted. For example, in many 70 MPH zones, the minimum legal speed is 55 or 60 MPH. You might be able to save fuel by driving slower, but you shouldn’t.
I disagree. Just getting to a speed where you can shift into top gear would use a lot of fuel, and then there’s the wind resistance at that speed.
My position is that the most fuel efficient speed is the speed achieved by shifting into the lowest gear and letting the engine idle. It’s probably around 4 or 5 MPH.
Yes indeed, it’s acceleration that destroys fuel mileage…
Back in the days…They would lay out a ten mile circle on the salt at Bonneville and mount a calibrated container of gasoline on the car, it’s only fuel source…They would then measure how far the car could travel on that measured amount of fuel…The test was repeated at different speeds. Using cars that had been “tuned” to achieve maximum mileage (like they did to the Mobilgas Economy Run cars) they could achieve some amazing numbers using professional drivers, not cruise control…
“Tuning” included optimizing carburetor “settings” (jetting). Using ATF as the rear-end and manual transmission lubricant. Removing the self-adjusters from the brakes and setting up the brakes for zero drag. Lubing the wheel bearings with motor oil, not grease. Using a low-drag or no drag cooling fan. Installing an oversize pulley on the generator or alternator. Optimizing the timing curve on a dyno. High-pressure tires. Dropping the nose of the car a little…Milling the heads to achieve the minimum factory combustion chamber volume (and maximum compression)
All these little tricks added up to some amazing mileage numbers…