romer

I couldn't copy/paste the whole article due to pictures. But it is very interesting for Toyota/Lexus Hybrids and getting the best MPG. Short answer is to use the ECO mode. The EV button can actually lower mileage. Here are some pertinent passages.

EV mode and Eco mode: One of them helps mpg

Why the difference? Simply put, Toyota’s hybrids are the ones with EV mode, and pressing EV mode does not help mpg.

Firstly, let’s look at what Eco mode does. Toyota sums it up as remapping throttle inputs and optimizing the climate control system for conservation.

In Toyota’s owner’s manual for the RAV4 Hybrid, for example, it explains the mode a bit more. Eco drive mode improves fuel economy through two differences, it says—by “more smoothly generating torque in response to accelerator pedal operations” versus the normal mode, and by “restraining air conditioning system operations (heating and cooling).”

…And now for the confusing part: Most if not all of Toyota’s hybrids have BOTH Eco mode and EV mode—and EV mode serves a quite different role.

What does EV mode do in Toyota hybrids?

The point behind EV mode might sound efficiency-minded. But Toyota engineers have in the past told this correspondent before that EV mode is not at all intended for maximizing fuel economy—and that using it might actually result in lower mileage as the system draws from vast data maps, looking at various parameters (some predictive) to decide when to run the engine and when to rely only on the electric motors.

Bottom line: Toyota hybrids are already optimized for efficiency to the point that almost anything you change, except for slowing and smoothing your driving habits, and running in Eco mode, is likely to cut mpg. And that includes using EV mode.

“EV mode is not specifically designed for fuel efficiency,” Brown confirmed. “The vehicle can be driven in residential areas or indoor parking lots early in the morning or late at night without worrying about noise or exhaust emissions.”

n the 2023 Toyota Prius owner’s manual, Toyota also gives an extensive list of situations in which EV mode may not be permitted, such as when the temperature is especially high or low, when the vehicle is already traveling at high speed, or when accessories like the windshield defogger are in use. Toyota suggests that typically that allows an electric range of up to 0.6 miles.

And there in the Prius manual Toyota clearly lays it out: “The hybrid system is designed to achieve the best possible fuel economy during normal driving (using the gasoline engine and electric motor [traction motor]). Driving in EV drive mode more than necessary may lower fuel economy.”

…In the meantime, trust the hybrid system and keep your hands off EV mode. And if you’re really that eager for all-electric motoring, find a way to get an EV.

Droid13

Makes sense. Other than some regen from slowing, most of the electricity is generated by gasoline. EV mode forces the battery to discharge more than it would in typical hybrid driving, thereby forcing the engine to run more to bring the charge back up to normal driving level immediately afterwards and maybe not in the most ideal situation. And charging/discharging the battery is not 100% efficient either, so you lose a bit going in and lose a bit coming back out. Unless you are using EV mode driving in a situation where you can immediately pickup a lot of regen (about to descend a hill), or going out on a steady and reasonably fast speed where the engine would be running more efficiently already, you'll just pay for it later. Other than special occasions or fun, EV mode is normally best left to the guys with the extension cord.

E46CT

^yep. no article needed. EV mode is just for those rare times you want to move the car around or drive for very short period of times (say exit your neighborhood) without the ICE kicking on. Basically it's for noise abatement and when you don't need to or want to spin the engine up only to shut it back off. It will (if the car allows) lock the car out of spinning up the engine. If the state of charge of the hybrid battery is low enough though, the car will override and kick the engine on. It does have its uses. I used it from time to time on my ES H when i had it. But I never used it for "fuel economy." not sure who does that.