Why such a big difference?

In the UK we do not have the thermos but i agree that a warm return trip would make a big difference.

 

One additional thing to keep in mind is that when dealing with higher mpg numbers, variation can appear larger than it really is. For example, a 15% change in mpg for a 25mpg car will result in a tighter variance than the same 15% change for a 50mpg car. The end result is still a positive savings in fuel regardless of the variation.

 

Hallo Adrian,

Temperature has a big impact on fuell economy, especially on a hybrid.
So in winter there is a big penalty on short trips.
If your Prius is new, it also is at it`s least efficiënt, because it needs to be "broken in", the engine is still new and all parts need to wear in on another.
I have a Toyota Auris Hybrid, yes, it`s made in the UK!
Here in the Netherlands we almost have no hills, so most of the time it`s flat as a pancake.
I have the car since October 28 and so far I drove about 3800 kilometers.
And I notice a slow increase of fuell economy.
Today I had to fill it up again, and for the first time my average fuell consumption was a little better than 20,2 kilometers per liter.
Now let`s go back to your question, why such a difference?
A Toyota Hybrid, No matter if it is a Prius or an Auris, is programmed to maintain the ICE at a given minimum operating temperature, and even if your battery is fully charched, the ICE will run in order to reach this temperature.
You can notice this, because you can run only short distances in EV.
It also does not shut down at stops for traffic lights, you must allready have noticed this.
But when the ICE is warmed up, it will shut down at every stop you make.
On the Toyota Prius Forum here in the Netherlands, I read about Prius owners who improved their fuell economy by blocking the grill.
Also on this forum you can find information about the benefits of grill blocking, and it makes sence.
The wind coming in through the grill cooles the ICE down on the outside, and as soon you drive in VE like it will loose heat quickly!
Therefore I have blocked my grill, and I noticed the ICE warmed up a lot faster, and longer distances can be done in EV.
But read about it elsewhere on this forum, before you consider to block your grill.
It also depends on ambient outside temperatures, in summer the ICE and your inverter would heat up to much, in winter it would be fine.
Greetings, and have lots of fun with your Prius,

AEO

 

It has suprised me just how hilly some areas are, and i never noticed in my other cars! Once you're used to driving it, have a look at the HSI. you'll see when going up even a small hill the HSI is a lot higher than when coming back down - it makes a big difference since being in the middle of the HSI gets you ~75mpg, and being 75% up it gets you 50mpg.

Glad you're enjoying it! UK/Europe seems to be finally embracing the hybrid, they accounted for over 8% of all European Toyota/Lexus sales in 2010!

 

Simple, not really, but you had a tail wind going "home" and headwind going "there".

 

How much time was the car parked between legs of the journey? If parked only a few hours, the engine would use noticeably less fuel for warmup on the return.

Also, how much elevation difference exists between the two ends? From my rule of thumb of 1 gallon of fuel equaling about 10000 feet of climb, a 400 foot elevation difference is enough to explain the difference you saw, without any warmup differences.

 

I don't do much on the motorway, but in the summer we did go down to cornwall. 60mph all the way got us 71mpg. On the way home we did try 70 for a bit and it was more like 60mpg. Cruise control and Eco mode all the time for us. Generally we aim to go everywhere at 60.

Did you get the radar cruise package as well? that would be great for following lorries for a relaxing drive!

 

Yep, even when you're pushing it a bit it's still way better than a diesel! What was your previous ride?

 

Yeah i am stuck on Auto now! Will never bother with a manual again. There's a been a few people at my work running the numbers on the company car scheme, and figuring with a 2nd hand prius and 25p a mile for fuel they will be laughing. Both figuratively and literally at the guys stuck with X5's for another three years

 

The higher temps make a huge difference. last summer i managed a whole tank at 73mpg, and with the same driving i had a winter tank at 55mpg.

I'm hoping with my PHEV to get tanks in the 90's this coming summer