What is absolute best speed for highest mpg?

Bob Wilson has done exactly that. (except he does not live right at sealevel, 600 feet may be a better guess)



Near 60 MPH and near 75 MPH are relative high points.

Updated MPG vs MPH chart | PriusChat

 

Zero MPH consumes no fuel if the ignition is off.

 

My experience is around 70-80 km/hr. That's around 45-50 MPH.

 

We've got two options for getting into town. One's via freeway with 90 kmh posted limit. The other via highway with 80 kmh limit, with 50 kmh stretches at both ends. The latter's our much preferred route now. Easier on the nerves too.

 

How much distance is achieved?

DBCassidy

 

Looks to me as though its the slower you go, the better the mpg, at least to somewhere below 25mph

The 100mpg at both 25 and 19 mph looks like the maximum mpg readout on the display. If so, both may actually be better

 

Bob's chart indicates only that the max happens somewhere below 25 mph.

Some previous threads, and some equations from the Japanese hypermilers, point to a max MPG in the vicinity of 15 mph.

 

Well, I've watched the mileage at very low speeds, below 50 km/hr (30 MPH) and it appears the consumption goes up. Of course, at those speeds to be safe, you'd have to be in the city in traffic or in housing areas trying to avoid being hit in intersections, and even then, around here you stand the chance of being run over! I would NEVER try to extend the distance on a tank by going that much slower than traffic. You may drop consumption but you would run the risk of not making it due to being hit!

As an example for my impression (and that's all it is as I've not done measurements, just watched the readout and results at the end of the trip), heading home from West Edmonton on the Yellowhead where the speed limit is 70 km/hr I have seen my best mileage in my so far short ownership of Pearl S. I've seen consumption for the 15-20 km trip as low as 3.1 l/100 km, though I would guess the average over many trips is probably in the 4.1 range.

Remember, at really low speeds the engine will shut off and you will be running on the battery. This is NOT fuel efficient. If you watch the instantaneous consumption readout while driving in housing sub-divisions carefully to avoid intersection runners you will probably see what I see - consumption will reach a minimum around 60-70 km/hr and go up when you go very slow. This is probably because there is a "base consumption" of fuel vs time when the car is "on" and at very slow speeds you don't cover enough ground to get the distance number high enough to record good mileage.

 

As David ^^ said, you must keep the ICE running for maximum mileage at a steady speed. Probably 41 or 42 MPH. On a non-hybrid it would probably be the slowest you could go in the top gear. Of course if there are hills, traffic, etc. things change and it becomes a judgment call.

 

Here's a good webpage to read from Tesla. The Model S has a similar coefficient of drag and they seem to recommend 55 MPH.

Your Questions Answered | Tesla Motors

It's true that the slower you go the better the mileage, but you get diminishing returns because slower becomes less practical and potentially dangerous on the freeway.

 

Does the Tesla offer a hybrid? I thought it was all electric. The 55 mph in the Tesla advertisement seems to indicate the speed for a typical range on the battery, the maximum range might be slower. What is being discussed here is the steady speed for maximum gas mileage in an HSD hybrid, quite a different thing.

I agree too slow is dangerous on the freeway but that is really not relevant to the discussion. The OP ask what speed produced the best gas mileage under ideal conditions. No one is suggesting you drive 40 mph on the freeway.

 

Driving for maximum range in an EV should not be considered that different than driving for best MPG.

 

I checked the Tesla advertisement again and changed my post accordingly. I did not see anywhere in that page that 55 mph produced maximum range. I think they simply wanted to give people some idea how far they might go at a sedate 55 mph highway speed. Maximum range might well be accomplished at a slower speed. Reading the graph they provide maximum range in the Tesla might be at about 20-25 mph.

 

+1

 

Some people are way too obssessed about mileage. Yes mpg matters and mpg is the main reason for getting a prius but c'mon get a life and drive it like any other car. Hypermiling and all that is ridiculous, life is stresful as it is. When I'm on fwy I find myself going 70-75mph like aby other car and still getting 47 avg mpg

 

I take a 25 mile long drive once a week in my gen 3. On the way at 2pm on the freeway in heavy traffic I average 35mph and get about 58-60mpg

On the way back at 9:30pm with no traffic at 70 mph I get 44 - 45 mpg.
I have non lrr tires that suck up a few mpgs too.

 

Look at the grey curve in the above graph (for the Gen1) the shape of that curve will depend on your fixed load, if like me, you always run headlights it will be a higher MPH where the max MPG occurs.

Gen 1 and Gen 2 should have a 'poor' MPG in the lower 40s. Gen 2 can often match Gen 3 near 60 MPH, the only speed where it comes close.