My 2018 Prius Three is draining gas FAST

From the clues posted so far, I most suspect a leak somewhere in the pressurized/pumped portion of the fuel system. This would almost certainly be covered under warranty, unless it was caused by road debris damage just happening to hit in the right spot.

The MPG display should be reasonably accurate (slightly optimistic), so the 80 MPG display suggests that this excess fuel is not going through the engine.

Fuel theft from siphoning should appear while the vehicle is parked, not moving. Similarly, a pinhole leak in the gas tank (accidental or intentional theft) should be mostly while parked.

It might be worthwhile leaving the car sit for some minutes while turned on and Ready, then sniff around a bit for gasoline odor or even spillage on the ground. At this loss rate, the odor should be strong, not weak.

 

it would be more helpful to know how many gallons have been pumped so far.

maybe we'll find out next time o/p 'wakes up'.

 

is 'half a quarter' an eighth, or 12 and a half cents?

 

Do you park in an air conditioned garage or is the car at historic earth temp? Cali has been hot, if the traction battery is hot.... even a half hour drive isn’t going to cool it much, so, 65-75mph, hot, and stop staring at the gas gauge, watch the numbers.

What did you drive and what numbers did it get, the Prius hold 11 gallons(meaning it will drop twice as fast as a car with a 22 gallon tank) at 65-75 getting high 40’s for mph is reasonable, in a hot environment with a hot traction battery.

Take a drive at city speed for a few hours and watch the numbers, usually the dealers, while prepping the car leave it in ready mode so the mpgs start very low, and as is being said~~~~ it takes several tanks to get a good base figure for mpg, btw, be nice to the dealer, you catch more flys with honey than vinegar.

And stop watching the gas gauge

And like all forums, you can ignore mundane posters.

 

o/p already posted a pic of the numbers.

 

Her situation sounds kind of unbelievable, but you never know.

Before I ran back to the dealer, I would do one last experiment:

Zero-out all 3 odometers. Trip-A, Trip-B, and the Main odometer.
Then gas up the car--remove the nozzle when it automatically clicks off!
Then set the display so you are watching Trip-A, and just begin driving normally with the Drive Mode in "normal."
Don't fill up again until Trip-A shows you went 500 miles. (Or if you want, until the fuel light comes on.)
Re-fuel at that time, and then hand calculate the gas mileage. Divide miles driven by number of gallons put in tank.

Then report back here, to bisco. The Chairman.

 

Uhm, isn't rolling back that third one a federal crime?

Just do the first two.

 

Nah, I reset mine 4 times already. It only zeros out the mpg. But you knew that.

 

I don't think driving another 500 miles is necessary. If 3 fill-up can be documented with amount of gas put in the tank, total miles driven divided by the amount of gas purchased would give rough mileage. Assuming the three fill-ups are near empty indicator then it would be 9-10 gal each time. With 427 miles total miles driven, that would be ~15 mpg. If my brand new Prius mileage is below 40 mpg, I would not wait another day before taking it back to the dealer where I purchased it. There is definitely something wrong.

 

if i need 4 gallons, and i fill up, is it still a fill up? or does it have to be empty to qualify?

 

Yap, that's the qualifier. If the three fill-up was only 3 gal each, that would be 47 mpg which is still low, but nonetheless acceptable mileage. I hope OP comes back and tell us what the amount of gas put into the tank for those 3 fill ups.

 

i figure tomorrow morning.

 

I would call that a top off. I was thinking the same thing. That's why I suggested that maybe she start brand new… A complete drain and refill.

 

Save the receipts for documentation. How many gallons filled for how many miles driven, reset one of the trip meter (I use B) after each fill up. I did brought my Prius at Antioch on Aug 3, tho I don’t live anywhere near there.

 

...

Says something - is very odd. I'd try a different fuel supply place - I suspect that all the pumps at the place you've filled up have clicked off early.

 

The few times I've done just part of a tank, If it's more than about 3/4 full once added, it seems to reset the DTE as though you've filled the tank. But if it's close to empty, and I put $10 in till the price comes down later in the week, it didn't register on the DTE.

That's why I'm wondering if his tank was actually filled - I've had some pumps which obstinately cut-off early - all been MOBIL

 

Not sure - I don't do maths on Sundays.

Or any other day that ends in "day". Not now I'm retired.

 

With my Gen3, it takes several gallons (3 gallons? In the owners manual somewhere) in order to reset DTE, probably same minimum that must be put into an 'empty' Prius in order to allow a restart. Your Gen4 is likely similar.