Ideal highway cruising speed?

I am pretty certain my experience with the Gen II holds true for the Gen III. The sweet spot for great highway mileage is 65MPH. Anything slower and you're impeding traffic flow but you will obviously get even better mileage. I usually average over 50 MPG when I set the cruise for that speed. The conditions have to be warm, mainly flat, light winds to achieve this type of mileage. I am sure others do better than I as I don't exercise some of the techniques used to raise MPG. Even when I'm going 75-80 I still manage over 45 MPG!! To this day, this car still amazes me.

 

My preliminary data:

Perhaps it is time to begin making your own trip records and sharing it here?

• record start and stop locations - enough that we can find them on Google Earth to get altitude. Also wind direction and speed, temperature, tire pressure and use or non-use of air conditioner.
• reset trip meter once you reach cruising speed - this let's you record the distance, MPG and average speed w/o the acceleration overhead.
• [OPTIONAL] use a Garmin nuvi or equivalent GPS to record trip - this can provide a detailed speed and altitude record for analysis

Well if you ask it '12 times,' the answer is 42, the Answer to the Ultimate Question of Life, the Universe, and Everything.

Bob Wilson

 

This is what happens when driving too far on "flash" when ~4.2, half-gallons remain.

Bob Wilson

 

My experience here is Northern Utah, where the freeway can be a series of gentle ups and downs, and reasonably light traffic, I find a perfectly acceptable economy at 70 mph. I monitor the HSI gauge, and can maintain a lit ECO indicator at that speed. After a number of miles, I find the average will be just above 51 mpg . The indicated efficiency will decrease going up hills, but increase going down, while still maintaining the ECO indicator. 70 mph enables me to not be hazard with other motorist becoming frustrated. I do not drive in the left lane, because there are drivers that exceed the speed limit by quite a bit. I just let them pass.

 

I just took a 500mi round trip @ 70mph and returned to the same filling station and got 49.6mpg. I'm happy with that. Tires@42psi, AC on max and drivers window open 1/2in

 

Your trip is 370 miles which I would call a medium distance trip.
Lets run the numbers and you decide.

Fuel at $3.00 a gallon.

At 75 miles per hour it will cost you $22.25
On average your trip should run a with stop about 5 hours 15 minutes.

At 70 miles per hour it will cost you $21.00 in gas.
On average your trip should run with a stop 5 hours and 36 minutes.

At 65 miles per hour it will cost you $20.20 in gas.
On average your trip should run with a stop 6 hours and 4 minutes.

At 60 miles per hour it will cost you $17.92 in gas.
On average your trip should run with a stop 6 hours and 36 minutes.

I do long distance driving between Pittsburgh and Naples Fl. which is 1170 miles. There are things that go on at higher speeds with your mind. The faster you go over 60 miles per hour the more your mind has to concentrate on the road due to the increased speeds. It also puts you reflexes on a hair trigger also. The average person can not stay at that level for more than a few hours with out problems. This is what makes you so metally tired on road trips.

Second you are also putting much more stress on the suspension and drive line components when your traveling over 60 mph. Parts wear out sooner than need be.

At 70-75 mph my range in a car is about 15 hours before I have to pull over and sleep for a few hours. At a maximum speed of 65 mph my range goes up to 21-22 hours.

Now my recommendation is to set the cruise control at 65 mph, put on some of you favorite Cd's and lean back and enjoy the ride.

 

You make an excellent point. I would submit, however, at least from the mental fatigue standoint, geography can make a difference. I have lived in the East ... along I-95, and the traffic is unbearable .... and mentally tiring. I now live in the West, and the speed limit is generally 75 or more. Utah is experimenting with section where the speed limit is 80 mph. In Wyoming, 7o mph is very comfortable .... except when it is snowing.

 

"Ideal" is entirely a matter of your own perceptions and standards. As Bill's chart shows, and I see in my own experience, MPG drops off quickly at all speeds over 25 MPH.

 

The magic words are PLAIN WATER. Never ever drink anything with sugar, corn fructose syrup, or caffeine while on a long trip. That especially includes those flavored waters. Look on the label and see how much sodium they have in them. Drink one and you will want another one sooner than you think.
Coffee and soft drinks even Ice Tea all take your alert level up and two hours later when the effect wears off you come down lower than when you started. You then buy more Coffee, Soda or Ice Tea and the whole process starts over again. Each time the sugar or caffeine high lasts for shorter period and you drop even lower than before.

That 21-22 hours is from the time I step out of bed. The car is packed and fueled and I'm out of the driveway with in 30 minutes of getting out of bed. If your spending three hours packing and getting things together before leaving on a trip you have just taken three hours off your possible time behind the wheel. So if your range is 15 hours and you spend 3 hours getting ready your range is now around 12 hours.

 

I think you are over-simplifying an extremely complex issue. Your brain's required concentration is not simply a matter of speed. It depends on the road's ability to handle a given speed, and the weather and visibility. Your overall age and health also play a factor. A young 20-something has more ability to pay attention than an 80-something. A marathon runner can probably drive a lot longer than an obese person. Your eyesight plays a factor. Your stress level plays a factor. For every road condition, there's probably a "sweet spot" as far as your brain's level of concentration. Too slow, and you're pre-occupied with people constantly passing you and you find yourself spending a lot of time looking in the rear view mirror.

To further complicate the "mentally tired" argument, I'm a firm believer that situations that require more attentitiveness can be safer than those "relaxing" conditions. Conditions that continually require a lot of concentration will make it less likely that you'll fall asleep at any given moment, even if you are extremely tired.

I'm going to have to respectfully raise the BS flag on your 21-22 hours of driving in a day. I'm relatively young (42) and in outstanding physical fitness, yet there is no way that I would drive even 15 hours in a day unless my life depended on it. After "just" 8 hours of driving, I feel very fatigued and ready to call it quits. You must be superman if you think you can safely drive for 21-22 hours. There's a reason that the FAA limits airline pilot's daily hours behind the stick to 8 hours per day, and pilots really have only a few minutes of each flight when they need to muster utmost concentration.

 

Like I said my max range with caffeine and sugar rushes is 15 hours, but with plain water 20-21 hours. BTW I'm 49 and not in what you would call good physical shape. Yes I can lose more than a few pounds.

I've been doing this straight through 1170 mile drive three to four times a year since 1987. I love to drive and the time behind the wheel is easy to me.

Everyone is very good at something. With me it just happens to be long distance driving. I bet you're also good at something that amazes people around you.

Take music I have zero musical skills but I'm still amazed and love to watch someone play an instrument. Just because they can play an instrument well and I can't, I don't criticize them.

 

I've done it twice with my NHW11: first time to North Carolina to pickup a traction battery and a second time to pickup a second traction battery. I also use the same trick, 65 mph, plenty of water, and quality tunes (back then, XM radio.) Bathroom breaks with a little stretching exercise and when arriving after midnight, more frequent breaks and coffee.

The trick to long endurance driving is a calm and relaxed state of mind. Your seat becomes the "comfy chair" and staying hydrated. Kick off the shoes, pickup some tunes, and stay relaxed but alert. Stretching in place helps too and shifting your seating position including changes to the steering wheel and seat position. But most of all, do not be driven! ... that is the fast track to the ditch.

Bob Wilson