Optimum Highway Speed

In Pennsylvania, USA most of the company owned trucks are GPS limited to 69mph. Private owner/operators don't seem to have that same restriction.

 

Excellent point, and some states have a lower speed limit for trucks. I have friends, with perfectly healthy cars (including the Prius), that insist that they cannot get good gas mileage. I'll offer to take a ride with them on the freeway, with the condition that they follow an 18 wheeler without passing it. The driver will go crazy as the 18 wheeler will avoid braking and quick starts at all costs. At the end of the round trip, my friend will see good mpg. He'll also be extremely frustrated from driving slower and unable to accelerate hard for an hour- and will often return to the driving style in the fast lane that results in lower mpg.

That's why I've always suggested for people, struggling to increase their mpg, to follow huge trucks. The independent operators are even better, because they have to pay for their own fuel costs and this has a huge impact on their profit margin.

 

Not trying to be trite, but I don't understand the question. "Optimum" means, well I'm not sure what.

 

Cambridge dictionary says:

optimum
adjective [ before noun ]
UK /ˈɒp.tɪ.məm/ US /ˈɑːp.tə.məm/also optimal
best; most likely to bringsuccess or advantage:

A mixture of selected funds is an optimum choice for future security and return on investment.

 

Around here, I don't mind following semis on the tollways. It's LDA (Loony Detection & Avoidance), more than anything else.

If the posted speed limit is 75, it seems the natives will push it to 90.



Posted via the PriusChat mobile app.

 

That must be everywhere grrl!!!

 

I will second the mention of 52mph, not sure on the actual mpg achieved at this speed but yesterday in good conditions it looked like around 90mpg UK. I was busy using warp stealth but having set the multi screen to the hybrid system energy arrows I saw this speed on a flat dry road gave direct drive, ICE to wheels only, no EV. With the Gen 2 this used to be 47mph and it would give 75mpg UK.

 

My goal is get 60 MPG on my trips. I don't always achieve it but I try. I have found that in no wind level conditions, 65-70 MPH will yeild 60 MPG if I apply basic hypermiling techniques. Any hill or headwind will give a lower result.

A big adavantage on the gen 4 is the ability to glide up to 72-74 MPH. This allows for P&G (pulse and glide) in the 65-70 MPH area.

Over 74 MPH my MPG is reduced, as the ICE (gas engine) constantly turns.

Note: Generally, with the cruise control engaged above 65 MPH, the ICE will not turn off. This significally reduces MPG.

 

Back in the mid 80's I owned a Chevrolet Chevette diesel/5speed. It always got 45-50mpg. On a trip to Florida I got stuck in 150 miles worth of slow lane 50 mph road construction ( they were adding that 3rd lane on I-75) and after 3 hours or so of 40-50 mph I needed a pit stop. I fueled up and checked my mileage= 62 mpg. Keeping it under 50 mph sure made a difference

 

Check pg. 120 of the 2017 owners manual.
"EV indicator *2, 3 (This is on the Hybrid System Indicator display)
The EV indicator comes on when the vehicle is driven using only the electric motor (traction motor) or the gasoline engine is stopped."

The green EV indicatior (on the Hybrid System Indicator display) is what I use to know when the ICE is stopped. You can get the ICE to turn off very easily by letting off the accelerator pedal for a moment. The green EV light will come on, then come back on with the accelerator pedal gently until the bar disappears. That is the glide position in the pulse and glide maneuver.

The 74 MPH figure is what I have observed. It is not in the owners manual.

 

Can't believe nobody's posted the chart from CleanMPG yet

 

^ This is why I don't understand "optimum" speed. It's really a matter of picking your poison. There's a very linear correlation between speed and mpg, no flattening out sweet spots in that graph. FWIW we stick to secondary highways wherever possible, 50 mph max.

 

Mendel is right, but for me a quicker journey over a couple of hundred miles is more important occasionally...
.. OK, most of the time!

 

Original post was

Good point. Just what type of optimization. Speed, fuel ecomony, ride, etc..

 

I live near the DFW and can vouch for the poor driving. Speeding, tailgating, not signaling, it's no surprise our insurance is so high! Sorry to get off topic here!

 

Thank goodness that doesn't refer to the sky above DFW. Yikes!

 

I call BS on the chart unless they are talking Imperial Gallons. I get nowhere near 78 US mpg at 50 mph

 

Whoa! You mean there's another gallon out there in the wild West?