Hybrid mode help, and increasing MPG

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New member
Aug 9, 2014

I am a new owner of an Accord PHEV and am a little confused about when the car is in hybrid mode vs if it is ever in a full-gas mode.

I took a couple short trips today, and noticed a considerable difference in the mpg on both trips. I didn't have any EV range left, and was going from home to and from an errand - so same distance and same amount of freeway/roads. On the way there, my HV range went down 23 miles, for only about a 13 mile distance, and the accord said I got 32.5 Mpg. On the way back, I pushed the HV button, and I was pretty much 1 for 1 with the HV range and miles traveled - 13 mile decrease in the HV range for 13 miles travelled. The accord said I got 46mpg. Granted they were both short trips and range can vary, but I think 32.5 vs 46 mpg for basically the same trip is a bit much.

My question is - do I need to push the HV button for the car to be in hybrid mode? I'm worried I'm getting a low MPG after my EV range runs out and that the car is running in gas mode only (is that even possible?) if the HV mode isn't forced on.

I thought the HV mode was supposed to only be to save your EV miles for later, but I'm wondering if its for more than that.

Any tips from others about how to maximize your mpg?
Welcome to the group!

So ultimately the car has really "4" driving modes.
Driving mode 1; All electric motor. (tends to be available IF you have enough battery life, usually won't go over 65mph in this mode).

Driving mode 2; All gasoline engine (w/ some excess power going to charge battery when battery is really low or if 'charge hv' mode). Gasoline engine only will typically be if you are Cruising @ a constant highway speed or if your battery is EXTREMELY low (1 bar).

Driving mode 3: Gasoline engine generating power to drive the electric motor to move the car (This ONLY happens if less than ~45MPH, does this since the torque is very limited with just the gasoline engine. If > 45MPH, see driving mode 4 below).

Driving mode 4: Electric motor providing torque in addition to the gasoline engine (This will only happen if greater than ~45MPH, unless battery is EXTREMELY low, else it just becomes driving mode 2). This mode leverages the torque from the motor/battery-power to accelerate, and allows the gasoline engine to catch-up, with the intention of 'efficiently' switching over to Driving Mode 1 or 2 depending on speed and battery life remaining.

Ok now that those are out of the way...

The HV button lets you toggle between the 3 styles/configurations below:

a) When NOT in HV mode (i.e. when in pseudo EV mode)...The car will try to run in Driving Mode #1 unless: you request too much power so it will move into driving mode 3 or 4, OR you are cruising at a fast highway speed, in which case it will move into driving mode 2.

b) When IN HV mode (not charge mode), the car will try to use EV from 0-20MPH (from stop to start requires the most torque, so fuel efficiency is why). Obviously if not sufficient battery, it will try mode 2 to generate enough of a charge to the battery. Modes 3 and 4 will be used whenever accelerating. One thing I've noticed is when in HV mode, if your battery does have a charage > 2 bars, it creates an artificial limit. So for example if you have 6 bars...It seems to create a limit at 5 bars so it "pretends" it's out of battery life there and then reacts accordingly (sometimes it will break it's own rule and exceed this artificial barrier, but only in extreme situations). This is how the vehicle "maintains" the charge for later in HV mode.

c) When In HV Charge mode, Driving Mode #1 is disabled, Driving Mode #2 is given preference, but Modes 3 and 4 will occur when "required" for acceleration. Once battery is charged, it switches to style B (regular HV mode).

So now that the complicated explanation is out of the way and answer your question...
DEPENDING on how you drive, you can see how there are opportunities to align your driving habbits with the EV/HV/HV-charge driving styles. When you only have -2- battery bars, EV mode (a) will ultimately be similar to HV mode (b), however it will try and prioritize battery usage a bit more aggressively. As you get more power from breaking, it will use the battery first. Whereas HV mode (b) will be a little more conservative.

I find that If I have enough of a battery buffer, I can do very well in HV mode. If you are in stop-and-go traffic, but you wait so you can accelerate and then maximize your recharge on breaking..you will find that you can go a SIGNIFICANT distance in EV mode without using any gasoline. However you have to drive a little different like that.

IF you drive this car as an experienced hybrid driver (i.e. you've adjusted to hybrid driving styles with a Prius or Civic hybrid over the past few years), you're likely to take better advantage of EV mode setting. You really do need to drive these cars differently to take advantage of the best MPG.
If you don't drive it differently, OR if you don't want to drive it differently, then HV mode will likely pay higher dividends.
Again this is all as it pertains to driving w/ _2_ battery bars.

Hope this is helpful. This observation is obviously my opinion, but to validate...have someone who has driven a Prius for 4 years and got into the 'maximize fuel efficiency' mentality, then get someone who is driving their first hybrid car with this Accord..and you will see a HUGE difference in MPG results. :)

Again congrats on your new car and welcome to the club!