Just bought a new 2020 plug-in

Looks as good as an official Toyota sales brochure!

 

I've been using pre-conditioning a lot lately and I just noticed I was able to turn it on wtthout the car being plugged in. 3 years and I'm still leaning new stuff about the car.

I have a theory about trips that are longer than available EV range with a full charge. I got my second best mileage this way, but it also depends on the driver and the car, because the Prime doesn't behave the same for others who drove this way.
With a full charge put it in and leave it in HV the whole trip. With mine I usually still have between 90 and 100% EV left at the end and some decent mpg / liters/km ... If you can still manage efficient trips in the winter, the spring trips will show efficiency gains faster too..

 

So, I netted about an 8 percent consistent gain by adding this simple and cheap modification.

It does actually do a little better on HV if you have 30 percent or more in it. My winter driving at 85mph nets around 55-58mpg round trip. Though a 15 mile portion of that 72 mile each way trip is typically averaging 40mph. my trip to work usually gets me around 63-68mpg and the trip home normally between 80-95mpg.

 

@GregersonIT Have you seen many other Primes during your daily commute?
You're the first I've seen post here at PC with those details in your daily routine.

Can you describe the difference(s) between the morning and evening trips that might explain the mpg difference? topographic (uphill / downhill), head and/or tail winds.

I've been around the speeds a few times on longer 500 / 1000 mile trips, but they are few and far between and usually north / south so temps are typically much warmer after driving 500 of a 1000 miles south, which I believe explains a lot about the mpg averages I see on those trips.

At a typically 85 mph I'm sure the fins you installed do help. If you look close around the side rear view mirrirs and on the tail hips just below the hatch you'll see some of those thing (I forget the technical name ATM) built right into the Prime body panels

 

It's stated in the owner's manual that leaving the battery near 100% charge causes battery degradation. The battery should ideally be charged just before EV driving—that's why scheduled charging is provided.

 

No one says anybody has to leave the car with a full charge for extended periods. One might think that if the car believed having 100% charge in HV mode and it was not meant to be there the car would use it without the driver having to press any buttons. Which in my experience the car does use it, but for me on my trips typically only between 10 and 20% which it typically puts back into the pack while on the trip, automagically like.

 

Oh, that does permanent damage on the paint and depreciates the value of the car a lot. I don't know if they have a significant impact on the drag coefficient.

I am not sure having some charge helps improve the HV mpg. I think it does in certain conditions, as you can have more optimized EV driving with longer EV stretches. However, with Prius Prime it's hard to measure the true HV mpg as it always uses some EV battery. Even when storing, starting, or idling the car, the EV battery could be depleted by several percent. Considering that each percent corresponds to 0.3 miles, a 5% depletion means 1.5 miles, and in a 10-mile HV driving, it would bogusly appear to have improved the HV mpg by 15%—in other words you would see 75 mpg instead of the true 65 mpg. Therefore, you need to account for the EV battery use, and that's tricky because it is even used during vehicle storage and start-up.

 

That's what you appeared to have said. I didn't know that you were talking about experimenting with driving with 100% battery in the HV mode instead of doing so regularly.

 

I'm guessing because I'm not sure which trip meters have been reset (by me mistakenly while pressing the trip button and taking pics at the same time of all the different screens on the MID that have trip data).For the fist 3 years I estimate about 75% EV to 25% HV mode driving. 3 1600 mile round trips in year one kinda clinched how far can I take this car in EV mode on the first tank like I did with my 2014 PiP.

 

I'm out in the central valley area of CA, commuting to the bay area. Yea, there are a lot of primes out this way. A lot... The fins seem to help at all speeds in excess of about 45mph. They really help with cross winds of which I regularly see 20-45mph on some days. I only needed those two and it made a sizeable difference. It's a slight uphill on the way into work, and slight downhill heading home so it's typical. Prior to the fins my best monthly average was 70mpg and normally getting 66-68mpg, after the fins my best monthly was 72.8mpg and normally averaging 69-71mpg. I do 3500-5500 miles a month. I still have the first set of tires.

Not bad for a 12 dollar mod though.

 

My biggest concern here in the snowbelt of NY is the winter temps. The first 2 years I'd put a space heater inside the cabin both while plugging in and pretrip. (lessons learned from grid charging a older hybrid pack in the cold ) I'm not doing that this year and my EV range is dropping like a stone as it gets colder by the day.

 

Look at the picture of where I placed the two of them. They are on the plastic piece on the back. A piece that's actually very very easy to replace and pretty cheap to do so. not to mention pretty much zero damage to car. I added them specific for cross wind resistance which they do very well because I regularly see cross winds of 20-40mph. My fuel mileage happened to increase at least 8 percent as a result.

 

I ran into some resistance here at PC when I reported 72 mpg on the first leg of my first 1600 mile round trip in Sept 2017 north to south. That is why I kept my responses to your reports quite initially.

That kinda mileage is hard for some to fathom, even some seasoned prime drivers. My best to date is on the 100 mile round trip in HV was 58 first leg (50 miles) against a 30 mph headwind and 91 return trip (50 miles) with the wind. Speeds were around 55 mph both directions.

 

HV mpg depends on a lot of things, including ambient temperatures (higher the better), driving speed (lower the better), and the gentleness in the use of both pedals. You need to make sure to account for the EV battery depletion. In my experience the EV battery could be depleted from 100% within a matter of a few days even in purely HV driving. Subtract about 30 miles from the HV distance for every 100% depletion and then redo the mpg calculation. HV mpg also strongly depends on the altitude change and it's important to report it for round-trip driving.

All this said I think 65 mpg is easy to achieve in the eco mode with some hypermiling, whereas 70 mpg is possible but pushing it. I try to break in to my new car very gently, hoping that this would improve the lifetime mpg. Switching to the API Group IV PAO-based Mobil 1 0W-16 may also improve the mpg with used motor oil, as PAO lasts longer. Used motor oil robs several percent of the mpg; so, it should make a difference when a longer-lasting oil is used. I think 75 mpg is possible in warm climates.

 

There are always those who have some doubt lol. I just put up the numbers and let those speak for themselves.

Yea, I actually get better mileage in normal mode on the highway and eco around town. Here is one of my trips as a way to mess with everyone. This was not long after the fins in June. Just happened to get the wind in my favor with traffic etc. On the 27th I didn't charge at work that day so it dropped my mileage a bit. I typically charge at work and at home.

 

It is a very civilized, modern car for sure, and the 2021 model is even better with the TSS 2.0!

Last night I got 85 mpg (96 mpg before accounting for the 5% SOC drop) in HV driving on a 17-mile trip, mostly freeway during rush hour. I seem to be averaging around 75 mpg, and it hardly ever falls below 70 mpg.

 

Cold weather hypermile-ing takes a Lot more attention to detail that most have little time and/or patience for. Besides testing driving modes, I used to stay in Normal all the time when the car was new and only tested Eco and Power occasionally, there are other ways to defur the cat.
I don't believe my shutters ever closed since new and rather than pay the dealer to switch it on and have them give me their story, i just put in my own block like I've been doing for 10 years plus I think it works better than the shutters, anyway. There's not really much anyone can do about the cold air intake and other losses a gas engine sees in winter weather, but when the weather turns warmer and the right conditions are met, the Prime really shines.

 

It's so easy to get 70mpg if you never have to get up to 80+