I have previously stated that the mode controls basic function was to modulate the amount of throttle you needed to apply to achieve a certain RPM/power level, with the Eco mode demanding the most travel in the gas peddle and the Sport mode requiring the least. This statement was only partially correct. The mode selected also controls when and how easily the electric motors kick in during acceleration, with the Eco mode kicking in the least (provided you gently depress the gas pedal while accelerating) and the sport mode turning on the electric motors the soonest with the least amount of 'throttle'. Better fuel economy is achieved regardless of the mode selected when you limit the electric motors from coming on during acceleration.

I have found that by controlling your acceleration in a manner that keeps the battery assisted electric motors off (so you are charging the batteries while accelerating, not using the batteries to help you accelerate faster), you can gain many additional MPGs per tankful. So you want to accelerate as quickly as possible without the electric motors coming on whenever possible - this maximizes fuel efficiency (while minimizing driving fun for some). By using this technique, I managed to have very respectable averages through the summer where my a/c was on all the time, and am now enjoying one of my best 'tanks' fuel economy wise, easily surpassing my pre-summer averages now that the weather has cooled and I no longer need the a/c. I am currently averaging just over 47mpg after about 400 miles.

Also, contrary to what some have stated in other threads, the mode selection does not affect the air conditioner in any way. While some Toyota products did have an a/c ECO button, this vehicle's a/c is unaffected by the Eco driving mode.

 

I quote from the 2013 ES brochure.

"DRIVE MODE SELECT
Customize the performance of the ES with Drive Mode Select.
In ECO mode, a calming blue light surrounds the gauge cluster while climate and throttle settings are optimized for increased fuel efficiency."

And, from page 297 of the ES 350 and ES300h manual.
"Eco drive mode controls the heating/cooling operations and fan speed of the air conditioning system to enhance fuel efficiency. To improve air conditioning performance,... turn off Eco drive mode".

I would also question a couple of other things that you have said, but, since my ES is not the hybrid, I won't comment on them.

 

Ok, so how do I tell when the electric motors come on, when accelerating? its not the eco light, right? I never see that when accelerating hard from a light.

I have my left dial set to throttle position always. but don't know when I use gas and electric power.

 

I think the only way to know this is if you have your dash display showing the real-time energy usage of the vehicle (with the battery, engine, and wheels and arrows).

 

"...dash display showing the real-time energy usage "

Yes, that is correct. I always have that displayed, which is how I discovered what was happening, in conjunction with the tachometer display. You can accelerate at a much higher RPM without battery assist in ECO mode. I believe when accelerating in this manner, overall fuel efficiency is probably in the 30-35mpg range (combined gas and future electric only use).

Based on actual use of the a/c system during a very warm Florida summer (many days 95+), I can assure you that the a/c is not affected by the ECO mode. Florida summers tax all a/c systems and I have tried the various modes and the a/c system works equally well regardless of the driving mode selected.

 

I must say, it very rarely happens to me that both the ICE and electric engines are engaged when accelerating. The rare times when the electric engine assists in acceleration is when the hybrid battery is almost completely charged. (Note: I drive in Normal mode almost 100% of the time).

I think the system engages the electric engine as the hybrid battery is maximally charged, thus "charging" the battery is useless, so the system spends that energy in assisting acceleration, to "improve economy".

 

You can also see when the electric motor kicks in with the Nav screen, essentially a larger graphics of the dash. I've split that with the map display, which is more interesting than seeing the bar chart on the trip info/fuel consumption.

I do notice the electric motors assist with the ICE during stop and go traffic, when I accelerate moderately. I'm going to try Elliot's technic but how do you NOT get them not to kick in? If you accelerate slowly, you're under electric power anyway. If you drive aggressively, they both kick in, and that's not too practical in stop and go traffic.

 

"but how do you NOT get them not to kick in? If you accelerate slowly, you're under electric power anyway. If you drive aggressively, they both kick in, and that's not too practical in stop and go traffic."

You achieve this by modulating the throttle. I find that acceleration at about 1700 RPM in both ECO and NORMAL modes will achieve the desired result. ECO mode has the advantage of allowing higher RPMs much of the time for acceleration, especially above 25 MPH, giving me the ability to accelerate at 2500 RPMs and higher - the faster you go, the more throttle you can apply without the batteries kicking in. To maximize fuel efficiency, you want to accelerate as quickly as possible to cruising speed without the electric motors kicking in, when possible.

If you are accelerating too quickly, back off on the throttle until the electric motors are no longer being used. Again 1700 RPM seems to work all the time except in SPORT mode.

I have not yet determined whether accelerating only on electric power helps or hinders FE. At this point, I typically will accelerate under electric when I can, but there are times when it makes sense not to, For example, the worst thing you can do with regards to FE is to be stuck at a traffic light with a very low batter, which will cause the ICE to come on. If my battery is pretty low, I will get the ICE long before I get to a traffic light so the ICE remains off at the light. Hybrids, like any vehicle, get their worst FE when stopped and the engine is running (to charge the batteries).

 

While I can understand and accept the logic in your explanation that says that getting to cruising speed quickly can enhance the system's ability to charge the battery, a question would still remain, and that question relates to whether the process of getting up to speed more quickly might, in fact, be using up more of the battery's available charge than would be used up if acceleration was more moderate. I suspect that there has to be some trade off because, when you are using higher rpms, more power is being consumed, regardless of whether it is battery power or power from gas. Thus, while it may be the case that accelerating more quickly allows the battery to charge more, it may also be the case that this gain is offset or, perhaps, surpassed, by the additional drain on the battery caused by that more rapid acceleration. I have no idea whether there is a net gain or a net loss, but logic says that there has to be an offset.

 

"whether the process of getting up to speed more quickly might, in fact, be using up more of the battery's available charge than would be used up if acceleration was more moderate"


You are absolutely correct. As I previously stated, that you want to accelerate as fast as possible without the electric motors coming on (this applies for those times when the ICE is on).

 

Thanks guys!

I'll be switching my display from the bar mpg mode to the energy use mode and watching that for a change...

 

Mr. Bill, let us know your results. I have had a 15% (or more) increase in FE and I attribute it all to the change in how I accelerate.

 

Thanks Elliott. My FE is up, but that may be due to my monitoring as opposed just driving. Time will tell.

 

I just completed my first tank since not needing my A/C (due to weather changes) and achieved my best FE to date, averaging over 48 mpg after driving about 675 miles, a gain of about 6 mpg from what I was getting before the summer. My main difference in driving style has been how I accelerate, as I described in my original post.