How Low Will It Go?

[Arifax]

I got my ('06 T-Spirit, 80k) Prius in August.

I had seen on the forums that mpg gets worse in cold weather.

Until last week when the temperatures dropped, I was getting just over 50mpg without any difficulty - more if I made a special effort at economy driving.

It's not exactly winter yet but the mpg has plummeted to 42. I sit at traffic lights expecting the engine to stop, but it doesn't - presumably trying to keep me warm! I have the a/c set to 20 degrees.

How much worse is it going to get? It is burning fuel almost as fast as I am shedding tears!

Geoff

[kithmo]

I had 39mpg last winter in the heavy snow/frost, leaving the car idling for 15 minutes to thaw it out before setting off every morning.

One trick with the heating is to put the car in eco mode, this lowers the output of the heater and the engine will cut out more readily when idling in traffic.

[Flaninacupboard]

The traffic light engine run for cabin heat is annoying. I turn the climate system off when i'm not running the engine, and wear a coat.

Last summer my best tank was 73.3MPG, in the winter on the same driving i was seeing high 50's.

Engine block heaters would help a lot, i will see how i get on this winter with the plugin kit installed and may fit one in the spring.

[Grumpy Cabbie]

Check your tyre pressures too. A big change in temps (like at the moment when it's gone really cold) will affect the pressures - air expands, contracts etc.

[timberwolf]

Has it already got down to winter temperatures in the North!?

I was surprised to see a little frost on the car this morning, but I haven't had to drive my car today.

That 42 mpg does seem low - is that a fill-up calculated figure or from the car's computer?

My lowest was 45.5 mpg (fill-up data), two winters ago (I didn't drive last winter), with a typical destination being about 7 or 8 miles away. I try not to do shorter distances as it seems to take about 3 or 4 miles for the engine to heat up to the 85 C operating temperature when it is freezing, and it only does that if the car is being driven - if you get stuck in start/stop traffic from power on, the engine may not get up to operating temperature.

I had one journey where the engine stayed in the low 40C whilst I was stuck on the M27, because the road surface was being cleaned, but the petrol engine was cycling on and off all that time (and it had just been in for a service at the local dealer - so I was thinking that they had done something to my car during the service).

As your car is 5 years old, one bizarre contribution to a low mpg might be the 12V Battery. I'd test your mechanical key just in case the 12V Battery does fail this winter, and brush up on how to safely jump start the car.

[Arifax]

One trick with the heating is to put the car in eco mode, this lowers the output of the heater and the engine will cut out more readily when idling in traffic.

I don't think I have an eco mode - just an EV button which turns into a purely electric car. It refuses to do so more often than not!

[Arifax]

Has it already got down to winter temperatures in the North!?

I was surprised to see a little frost on the car this morning, but I haven't had to drive my car today.

That 42 mpg does seem low - is that a fill-up calculated figure or from the car's computer?

My lowest was 45.5 mpg (fill-up data), two winters ago (I didn't drive last winter), with a typical destination being about 7 or 8 miles away. I try not to do shorter distances as it seems to take about 3 or 4 miles for the engine to heat up to the 85 C operating temperature when it is freezing, and it only does that if the car is being driven - if you get stuck in start/stop traffic from power on, the engine may not get up to operating temperature.

I had one journey where the engine stayed in the low 40C whilst I was stuck on the M27, because the road surface was being cleaned, but the petrol engine was cycling on and off all that time (and it had just been in for a service at the local dealer - so I was thinking that they had done something to my car during the service).

As your car is 5 years old, one bizarre contribution to a low mpg might be the 12V battery. I'd test your mechanical key just in case the 12V battery does fail this winter, and brush up on how to safely jump start the car.

Argh!

So much I don't know.

For example, how do you get a read out of the engine temperature?

My figures aren't personal calculation - just from the computer. I see it also lies to me. If it was honest, it would show the engine as running and charging the Battery when stationary at traffic lights, not displaying engine and motor off as it does.

Geoff

[timberwolf]

Sorry, I should have said, I'm reading the engine temperature with a gadget that plugs into the diagnostic socket located in the lower dash just above the brake pedal.

Erm, to be honest, the extra information is a bit of double-edged sword, it is nice having the extra gauges, such as engine temperature and rpm, but it can also cause consternation when the engine management system is in a mode (or should that be mood?) where it is doing something you haven't seen it do before.

[Arifax]

Sorry, I should have said, I'm reading the engine temperature with a gadget that plugs into the diagnostic socket located in the lower dash just above the brake pedal.

Erm, to be honest, the extra information is a bit of double-edged sword

That's as may be, but I want one!!

Where do you get them from?

Arifax

[johalareewi]

Scangauge 2 is the best for a Prius because you can customise the X gauges to get lots of extra data. There is lots of help over on Prius chat for programming extra features.

http://www.scangauge.com/

[johalareewi]

I don't think I have an eco mode - just an EV button which turns into a purely electric car. It refuses to do so more often than not!

Press the ECO button (the one next to the EV button).

[Arifax]

I don't think I have an eco mode - just an EV button which turns into a purely electric car. It refuses to do so more often than not!

Press the ECO button (the one next to the EV button).

I have an EV button and next to it a switch-sized indentation in the plastic but no switch.

Can I have yours?

Geoff

[Grumpy Cabbie]

I don't think I have an eco mode - just an EV button which turns into a purely electric car. It refuses to do so more often than not!

Press the ECO button (the one next to the EV button).

I think he's got a gen2 2006 Prius. They don't have the eco mode (well I don't think they do).

[timberwolf]

Scangauge 2 is the best for a Prius because you can customise the X gauges to get lots of extra data. There is lots of help over on Prius chat for programming extra features.

http://www.scangauge.com/

Yep, I have an SGII. I would say it was functional rather than pretty, but it is relatively compact. Some features to think about when looking at these devices is whether they work well with hybrids, a) do they keep on displaying info when the internal combustion engine (ICE) has stopped, and B) can they display any custom information such as HV Battery Amp, or Battery State of Charge.

Or if you have a spare laptop, you can could go the DIY route, with OBDII dongle/adapter and some linux software.

[johalareewi]

I have an EV button and next to it a switch-sized indentation in the plastic but no switch.

Can I have yours?

Geoff

Whoops.

[Habu]

I regularly get as low as 8mpg!!! If the traffic is moving albeit slowly then no probs but if it's stop / start traffic over a long stretch, like the M62 at rush hour, then each time the drive Battery goes flat the engine will kick in racing and the mpg plummets Saying that, I can regularly hit 70mpg in the summer too.

[kithmo]

One trick with the heating is to put the car in eco mode, this lowers the output of the heater and the engine will cut out more readily when idling in traffic.

I don't think I have an eco mode - just an EV button which turns into a purely electric car. It refuses to do so more often than not!

Sorry, I was thinking Gen 3, didn't notice your sig with 2006 in it. You'll have to go with turning the heater off when stood in traffic then.

[cbcdesign]

Its pretty sad if people are going to whine about their cars only getting forty to the Gallon in Winter! Its still prefectly respectable compared to other cars on the roads. You should Drive Jags for a few years and you will learn to appreciate 40MPG!

I think some Prius owners could be well on their way to becoming obsessive compulsive over fuel consumption with these cars!

The day I turn down heaters to save a few MPG is the day I give up driving altogether!

[Arifax]

Its pretty sad if people are going to whine about their cars only getting forty to the Gallon in Winter! Its still prefectly respectable compared to other cars on the roads. You should Drive Jags for a few years and you will learn to appreciate 40MPG!

...

Fair comment, but it does get to you after a while!

I traded a 14 year old Mercedes S Class (which was developing compression problems) for my Prius. I was struggling to get 14mpg and thought 40mpg would be heaven (cutting £100 off my average monthly fuel bill).

After a few months at 50mpg, I can't help resenting a drop to 40 mpg and have to remind myself that 40mpg was what I aspired to!

Jags? I love them. My heart belongs to Jags and my head belonged to Mercs. I alternated. Best car I ever had? A V12 Jag (when I could get all 12 firing). "12" meant mpg on a good day as well cylinders.

Geoff

[johalareewi]

+1

I was getting around 30mpg in my previous car and was hoping to get 45mpg in the prius.

Now I get in the 60s for mpg in the summer, i do feel a bit miffed that I am in the low 50s in the winter.

[sjrainsford]

My Gen 2 bottomed out at 49mpg last winter. Summer driving has seen 54. I tend to just drive it and not the most economical way.

[Grumpy Cabbie]

My worst tank was 39 mpg (displayed 41mpg) in the middle of the bad winter 2009/10. (I left the car running to keep me warm between jobs).

[Opifex]

When deciding to buy the Prius I had been calculating the savings based on 60mpg average. I collected the car on 14th December last year and was very disappointed by the first few fill-ups which were around 49mpg. Heretical thoughts passed through my mind, such as why didn’t I buy the BMW.

Smiles came in January with the warmer weather (in France) and the mpg immediately started to rise. Average from May to September was 57.5mpg, with one fill-up that reached 69.99mpg.

So, I haven’t quite managed the 60mpg I’d hoped for but not too far off. Trouble is if the mpg gets down to 55mpg I start to get depressed about it until SWMBO reminds me that the old Saab’s average was about 31mpg.

I have to admit I’ve become a compulsive mpg watcher.

[Grumpy Cabbie]

You sure you have 0w20 in your car? You should easily be getting mid 60's on a run if you take it steady. Our road trip to France last year came back with an average of about 64 mpg including some stretches on French motorways! ;)

[Opifex]

You sure you have 0w20 in your car? You should easily be getting mid 60's on a run if you take it steady. Our road trip to France last year came back with an average of about 64 mpg including some stretches on French motorways! ;)

Didn't notice any difference after the recent service which said 0w20 on the job sheet so I assume the oil has been right all the time.

Perhaps the answer is in taking it steady. Roughly a third of the miles this year have been on French motorways cruising at 75mph and rising to over 80mph on occasions. A large part of the rest has been local trips of a few miles when the car hasn't had a chance to warm up properly. Neither of which are ideal conditions for the Prius to show it's abilities.

I've found that if I drop the motorway speed the mpg does rise rapidly but it's very difficult to cruise at less than 70mph when you have a speed limit of 80mph and 800 miles of relatively empty motorway in front of you.

At the other end of the scale I did see an indicated 80mpg after a 50 mile trip cruising along rural roads. :)