Sudden Significant Drop in MPG!!! 50 to 40 overnight!

Out of curiosity: when camping are you using the car’s electrical systems, and if so, in what ways? Please be specific as possible. Thanks

 

You can just leave the car on and the ICE will run every so often to charge the hybrid battery backup. Make sure you turn off the headlights though.

 

yes, we have a whole forum on it, great applications, camping and emergency generator

 

I don't have any other methods for triggering the MAX EV State. It is the most frustrating and confusing problem ever and results in on average me losing $5 worth of gas a day on mail routes... taking mpg from 45 to 35 in my Gen 2. And literally no other Prius owner knows what I'm talking about. Which is why I'm on a quest to prove it.

I just went to a dealer a couple weeks ago and talked about what I was experiencing... and they kind of just wrote me off but were impressed with my knowledge of the Prius. I told them I'd come back when I have proof.

The only other user I've found who has recognized the scope of this problem is user @kirill626 in this post: Possible undiscovered performance and MPG issues with Prius v (lowercase v) Drove him crazy as well and many didn't believe him.

I would get access to a Bluetooth OBDII device and use something like Dr. Prius to read temps and monitor data which seems like you're working on anyways.

I'm working on getting a video out about this... Just finished writing the script yesterday and will be filming it shortly.

Posted via the PriusChat mobile app.

 

Thanks, that does answer my question. When you say you don’t turn off the ignition, do you mean you leave it in the Ready mode (as though you were driving) or do you put it in ignition mode? Do the other members of your family also camp with you or elsewhere and use their Prius’ the same way?

 

Hopefully your problem has fixed itself. I know we're all paranoid our battery is going out. But poor gas mileage can usually be chalked up to something more rational, like our driving habbit.
Prius is a very fickle car. It wants perfect weather, no weight and a cats paw on the gas pedal.
But relax , my man, you got a toyota! Its gonna outlast a tesla. Boom! Lol

 

Ouch! Seems more serious than i thought.
You should be getting much more than 40mpg on a gen4.
Make sure youre driving in NORMAL mode. Not ECO.
Disconnect the 12v battery for a couple hours. That should do a hard reset on the car.
Also download the DR PRIUS app.
Look thru the app and find the proper OBD scanner to use. You will most likely have to buy one off Amazon $30-50 range.
Also...whats the mileage you have?
My vehicle isnt as efficient as it once was.
But with 100k, im still easily getting 52 in mixed driving. Gen4 prius2. Nimh

 

On the DR PRIUS app....full disclosure , i have not used it yet. But plan to.
Its supposed to give an estimate on the battery life left. Many people say its legit. Im spreading the word on good faith.
Good luck, buddy. And keep us informed

 

Hey buddy, also on the passenger side, back seat, theres some vents located on the base of the seat. That's where the battery breathes and cools. It should never be covered and theres a filter that needs to be replaced, behind the vent.
The vent is part of the plastic base of seat.but easily snaps out and snaps back in. I think theres one plastic fastner and maybe 3 snaps.

 

a 10 MPG drop is large Brakes that drag could cause a loss in any car ,.You could try a low speed coast to see if car shimmy's to a halt
as you say from a stop it goes into EV mode try driving 4MPH & see how long it stays in EV mode .
Going down an incline is a natural EV mode . You might have a crimp break hose .
I think if you could test all the fixable drag forces that could cause computerized non EV interference from a laymen's position you could come to a conclusion if its an interference related non computer .
A way to look at situation is - - your system is telling you , something is causing the need for low end power to soon .

 

I have a 2018 Prius 2. I now have 59400 mile on the odometer. Ok just got back from a trip from Denver to Chicago and back. New tires before I left. Was seeing the usual 55-60 mpg at 80 mph.
Traded seats with my wife. When I got back I was running 43mpg at 78 mph and 38 at 80 mph. I hadn't watched the power screen much. That is my wife's favorite. I am noticing that at freeway speed 55mph and higher the battery never gets charged. Coming back the cruise was having problems maintaining a set speed. In the past cruise on caused the car to rapidly accelerate to a speed and held it. Now, when a speed is set it drifts down 1-2 mph below the setting and tries to get back there. On the last leg, with cruise set if I gave more pressure on the throttle, the speed dropped at first. Called the dealer today and their first appointment for service is Nov31 a month out. Next step is to get my scan tool out and then head to my old bosses's shop he was working on Prius's for a while. I welcome any thoughts and I will update as I find out more.

 

To really see a fact go 60 and slip trans selector into B braking mode seems to be pure recharge when you coast

 

Let us know what you find out. I'm wondering if you had a battery cell go bad.

If I tell the cruise control to stop pausing, mine gently goes back up to speed - not rapidly like some cars I've had.