Took a 50 mile run today (25 miles each way) and with cruise set at 60 MPH I got 27.9 then the same trip at 70 i got only 24.8. THIS IS NOT AS GOOD AS I HOPED. Anyone ever try this??

 

Sounds normal to me... every vehicle typically get lower mileage as your speed increases over 55.

 

That does not sound that good. I rode in a RX330 last weekend and its average was 24.4 doing 80 on the interstates in the mountains.

 

At a steady 70 or 80 MPH, on flat terrain, I doubt that a hybrid offers any advantage over a non-hybrid as the gas engine is basically running full time under a moderate to heavy load from the wind resistance. The electric motors have little opportunity to provide any savings under these conditions as significant gas engine power is continuously needed to keep the vehicle going at these speeds.



I believe that the Highlander gas engine was detuned a bit for better mileage than the regular Highlander 6 cylinder engine under such driving conditions. The hybrid gas engine has a few less HP as a result.

 

A few months ago I went on a 250+ mile trip. With the AC on and cruise set between 70-75 mph I averaged around 24.5mpg. Your average sounds about right to me. The hybrid does very little at speeds above 60 mph.

 

FWIW, on a recent trip from PA to FL and back I figure I got about 26-27 highway MPG while travelling at the speed limit to speed limit +5 (max 70 mph). A/C was on the entire trip. My efforts were to get as high a MPG as possible while not being a danger to the other traffic, and I ended up not using the cruise control since I found I could do better myself. The low I got was 24.5, and that was using cruise. Perhaps you might try playing around without cruise to see if you can do better. Just my 2 cents.

 

Go slow and stay in the right lane, you will see an increase of at least 10-15%. Lots of folks have forgotten that the old 55mph speed limit was to save fuel during the first oil embargo.

For the last year, I've been driving at or a just below below the speed limit (60) in the right lane for our 125 mile trip to our weekend place. People do wizz by, but if you are in the right lane and plan ahead for the merges, its not too bad. On the few times we've taken the HiHy on this trip, we get just over 28 when going slow and the one time when there was lots of weekend traffic, our MPG was 31!.

I used to be a chronic speeder, using a radar detector since the early 80's, but now that fuel economy is my priority, I've learned to go slow. Downside is that I get sleepy going slow, but it only adds a few extra minutes to our trip time.

 

This would mean that a hybrid still should deliver slightly better mileage even under steady crusing (though the difference will close the faster you go), as that smaller/economy tuned engine is going to be more efficient, as it can rely on the motors for horsepower when needed. Also, the CVT might make a slight improvement as well.


The difference between the two figures is to be expected, as air resistance increases with the square of speed (doubling speed quadruples air resistance) but both numbers sound too low for level, steady-state driving.

This could be an explanation, cruise-controls will often "overreact" to small undulations in the road, and waste energy by accelerating hard over small inclines, then decelerating rapidly to maintain constant speed. A driver in the same situation however would maintain a more stable engine load and let the speed fluctuate.

 

We used our HIHY to tow our ~ 2,000lb trailer and boat last week. Approximately 600 miles, and we got 21.4 mpg.

I have convinced my husband to stay at the speed limit for better mileage. True, our trip was mostly flat terrain and no wind. He used the cruise for a while and then discovered he did better in the slightly hilly areas without it.

I read that you lose something like 5% mpg for every 1 mph over 65. And, if you watch for specific cars speed by, you will often see them later, visiting a trooper or just slowed down in traffic.


Since he bet we wouldn't do better than 16mpg (what he gets in his Buick Ultra when towing) I won a dinner out of my choice.


I noticed my HIHY, when not towing, gets better mileage now (up about 2 mpg to about 26.2) that it has 'loosened up" at >9,000 miles.

Now my experiment is to run 10 tanks of premium octane (an option I know) to see what it does to the mileage. If it improves even a couple mpg I will be even on the cost, and performance is supposed to be much better.

 

Don't have a HiHy... but in MOST cases higher octane will give you LOWER MPG.

High octane is for HIGH compression engines, such as those in small sports cars.
You should use the octane stated in your owners manual for best results as your car is specifically designed for that.

In my FEH, when I get 85 octane in the Rocky Mountain states, I get better MPG than 87 octane in other states. One time I put 93 octane in mine, and got 30 MPG over the highway where as 85 octane gives me 36+ over the highway.

Buyer beware!
-John