only 37 every time?

That is a little on the low side:

Toyota Prius V MPG - Actual MPG from 1,142 Toyota Prius V owners

lots of short trips?
New tires?

how many miles on it?

 

Are you getting a specific warning about battery cooling? That’s been reported before, and IIRC was due to battery fan and/or venting routes being dust clogged. Or fan defective, maybe due to overload with dust.

any pets regularly in the car?

Again, knowing the miles might help.

 

Cleaning the battery fan and ductwork is something you can DIY; takes a couple of hours. OTOH this is a service dealerships have been offering, around $300 USD, and they’re maybe more capable of verifying proper fan running.

transporting pets can exacerbate this; again, is that something you do regularly?

Regarding the 117k miles, and this is my personal vendetta: I’d look into cleaning the EGR (Exhaust Gas Recirculation) system, including intake manifold (has EGR passages).

Sadly dealerships and Toyota aren’t very helpful, will only replace parts, which alone are about a grand, and then there’s labour.

there’s a few independent shops that’ll do it right, for around $600 USD.

it’s a relatively complicated DIY, but doable by someone with an array of tools, comfortable to do oil changes and the like.

I’ve got an “opinion”, that neglecting the carbon build up in the EGR will lead to head gasket failure, typically between 150k and 200k miles.

anyway, see first 2 links in my signature for EGR cleaning tips. On a phone turn it landscape to see signature.

 

anyone can do the fan/inlet/duct cleaning, if they are willing. do it before the long trip.
when you get back, look into the egr circuit cleaning, very important.
what make and model tyres?

 

As someone who actually has a Prius v I will offer the following:

1. Low octane gas will reduce mpg maybe 2 mpg. Nothing to do with top tier additives. Some low octane generic pipeline suppliers are used by many retailers who may or may not add top tier additives. You can’t believe the 87 octane rating at some stations.

2. Driving faster than 60 mph on a regular basis will impact the nominal 39 highway epa number. A v has a higher numeric final drive ratio to handle more weight. That gear ratio reduces the epa number no matter what but really impacts mpg at higher speeds.

Where I live, the two lane state highways are typically driven at 60-65 mpg. Mpg is ok. Any freeway is 75-80 mph which reduces mpg to 38 mpg overall or less. A mix of highways will get about 40 mpg overall.

3. Driving habits and specifically braking makes a difference. Reasonable acceleration and gradual braking such that regen is 95% of the braking adds a couple mpg depending on route and number of slowdowns.

4. A weak hv battery will cost you 4-5 mpg. Weak meaning close to replacement, often creating fast discharges in a stopped in Ready AC on situation.

5. Tires make little difference as long as they are a quality brand like Michelins. The standard size is already bigger than a hatchback with more contact patch. Proper inflation minimizes the contact patch. I now run Michelin Cross Climate2 (ice storms now routine in Central Texas winters) with no mpg impact.

 

Dr Prius app is good for battery assesment, works with Carista bluetooth OBD dongle.

 

yes

 

Read about this message in the 2017 owners manual.

 

Give DIY a try; the dealership will really soak you, guaranteed.

I’m familiar with cleaning the hybrid battery fan and ductwork on Gen 3, not so much with Gen 4. Somone here must have done it? On a Gen 3 it took about 2 hours, by far the majority of time dealing with finicky plastic fasteners and catches. I was able to clean the fan without complete removal too.

 

It turns out the Prius v battery blower cleaning is easier than a hatchback, partially due to the sliding rear seats. The intake is different since it is under the rear passenger’s seat. A simple issue to fix is someone stuffed something under the seat blocking flow.

But the battery fan and it’s squirrel cage blower is more commonly the real issue if clogged.

This is a good video on the subject specific for a Prius v wagon.

 

ask the dealers how much, they're competitive. and ask local mechs if they would do it.