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Discussion Starter #1
When driving on the highway, what do you think the fastest speed is while still maintaining the best mpg?
 

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Lower speed, and a constant speed.

In my Prius, I'd get noticeably better fuel economy at 90 km/hr than at 110 km/hr. Not that I'd drive at 90 on main highways, but when I did drive at 90, I'd do better for fuel economy.

Incidentally, I just found this on an Australian government site when I searched for 90 kmh vs 110 kmh:

Fuel Consumption - Ten Top Tips for Fuel Efficient Driving

Fuel consumption increases significantly over about 90 km/h. At 110 km/h your car uses up to 25 per cent more fuel than it would cruising at 90 km/h. If your car is fitted with cruise control, using it during highway driving will help to maintain a steadier speed, which will save fuel.
 

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When driving on the highway, what do you think the fastest speed is while still maintaining the best mpg?
The hybrid system is active up to roughly 70mph. Above 65mph you will see increasingly worse mpg. There's no "peak efficiency" speed, since lower is always better. But if you must have an answer its 55mph.
 

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There's no "peak efficiency" speed, since lower is always better.
That is not quite true actually. Too slow a speed and efficiency suffers again, or at least it doesn't get better.

However, what you say is effectively true, since that "too slow a speed" is something like less than 30 kph, which is unrealistic for anyone to drive on a highway or even large urban roads.
 

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The hybrid system is active up to roughly 70mph. Above 65mph you will see increasingly worse mpg. There's no "peak efficiency" speed, since lower is always better. But if you must have an answer its 55mph.
This.

80 is worse than 75
75 is worse than 70
70 is worse than 65
65 is worse than 60
60 is worse than 55

What kind of MPG do you want and how slow do you want to go.
Yes, there is a bit of a curve, where you are going to drop a greater percentage from 75-80 than you will from 70-75.

Generally, a nice tradeoff between very good mileage and acceptable boredom level is around 65-70 for longer road trips, 60-65 for shorter trips.

My '08 Tacoma would pull 26mpg at 60-65. At 80 it was down to 22mpg.
 

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That is not quite true actually. Too slow a speed and efficiency suffers again, or at least it doesn't get better.

However, what you say is effectively true, since that "too slow a speed" is something like less than 30 kph, which is unrealistic for anyone to drive on a highway or even large urban roads.
Ya... generally the "best" fuel economy is going to be within 5mph of when the trans drops into overdrive, IF road conditions allow that speed to be maintained.

If slight hills are causing frequent downshifting, then a slightly higher speed would be a bit more efficient.
But really, below 60mph you're really splitting hairs and there is not going to be a notable *cost* savings... only bragging rights ;)
 

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RAV4 Hybrid is CVT.
 

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This is my first CVT in over 50yrs of driving, no complaints so far.
 

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The hybrid system is active up to roughly 70mph. Above 65mph you will see increasingly worse mpg. There's no "peak efficiency" speed, since lower is always better. But if you must have an answer its 55mph.
My wife drives hers at around 68 mph. Good thing the atkinson engine is only 150 HP.
 

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Discussion Starter #12
RAV4 Hybrid is CVT.
Nice I had no idea!! The reason why I made this post and asked this question was because I thought it was a 4-gear transmission. I figured when the 4th gear first kicks in is the most fuel efficient for higher speeds.

So for CVT does fuel efficiency stay the same when maintaining a speed up until the widest part of the driver cone?
 

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So for CVT does fuel efficiency stay the same when maintaining a speed up until the widest part of the driver cone?
Non-Hybrid:
RPM is more load dependent than speed dependent. There does not seem to be the typical lag when transitioning from level to uphill, RPM climbs smoothly to match the load. Same for acceleration.
Running cruise control uphill, I felt none of the "hyperactivity" that my 2.7 Tacoma had where it jumped from OD to 2nd and back and forth until I manually pulled it down to 3rd.

But there are still limits and you aren't going to be cruising at 75mph with the engine at 1500rpm, and of course, there's the matter of physics, where it takes twice as much horsepower to maintain 100 as it does to maintain 75.

The CVT is good for a couple more MPG over a standard 5spd automatic, but it's no magic box that allows you to disregard speed if you are wanting best efficiency.
 

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Today I drove about 80 miles with 75 mph in average and about 20 miles with 45 mph and my xle easily got 35 mpg when I came home. Normally for similar trips it's been about 32/33 mpg but today having warmer weather must have helped it go up.
 
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