Better MPG in summer vs. winter??

welcome!
yes, there are several.

are you saying that you had a magical vehicle that got better fuel efficiency in winter than summer?

 

The Prius feedback reveals it more starkly than a "regular" ICE vehicle, but all vehicles with an internal combustion engine get worse gas mileage in the colder weather of the winter. The Prius is no exception. HSD-Hybrid Synergy Drive is designed for efficiency, and for cleaner exhaust, and this all works at it's best once everything is warmed up. Which is why Winter and short trips affect the possible gas mileage. Also winter fuel blends have been accused of a level of impact.
Combine all the factors and you can expect your MPG to dip every winter.

 

Why Mileage Gets Worse in the Winter | PriusChat

Here is the summer-winter variation for my first Prius, a 2010:

Note that I live in an area needing much less summer AC and more winter heat than does your area.

They must have had horribly inefficient AC.

Prii were built to have more efficient AC than traditional cars, with the 2010 model year making a significant advance over prior versions.

 

My graph looks similar, except in liters per 100 kms, it's inverted lol.

 

Keep a fuel log for the life of your car, then build a spreadsheet and graph with MS-Excel.

I didn't use any pre-made apps, the task is simple enough to do-it-yourself on the fly.

 

I've just been using Fuelly for graph, but I do maintain an Excel spreadsheet, and was just thinking to bite the bullet, Google how to pipe Excel data to a graph. Give me a mo'.

Ugh, not good at this. Oh well, a couple of years, higher is worse, in liters/100km:

 

"Normal cars" A/C runs the compressor off the engine. This means it works even when not needed.

The Prius compressor is a three phase 201 volt AC motor that runs only when needed, and only as hard as is needed, so A/C is more efficient. It also means you don't have to run the engine to stay cool.

Sadly, the best way to heat the passenger cabin still seems to be to heat water with the engine. So in winter you sometimes burn gas to keep yourself warm.

It is not all about you though, cold oil is thicker and the engine and drivetrain work harder to move lubricants in the cold. Battery chemistry changes with temperature, Weather is different, etc.

 

Also the car shifts to different programming with colder ambient temps?

 

Also in winter, the car has to shove a lot of water out of the tire path, and this process consumes a lot of energy (fuel).

 

These types of spikes can be very well smoothed out by adding a weighted average line, as in my graph.

Mine was computed by figuring average MPG over several tanks ahead and behind. For best results, figure total miles divided by total gallons for those several tanks, don't merely average the individual tank MPGs. But there are numerous different ways to do it, e.g. some more technical folks may wish to apply gaussian weighting factors to each element. Others may prefer a simple moving average. Some signal processing folks may even have an FIR filter toolkit available to apply.

 

For comparison, (my) Fuelly graph. It's not that flexible though; as far as I can see it's either a few recent, or all:


But yeah, good in July, not so good in January.

 

heat is for wimps.

 

Weather in foxboro and philly today looks like the eastern seaboard is having a heat wave.

It was only 55 here today and overcast .

 

46 here, we were in sorts and tees.