MPG?

[mrmick53]

Hi again.

I do like posting on here, I find everyone very helpful and no snide remarks.

Could anyone explain why for the first couple of months that I had my Corolla I was getting 75 even 76 MPG occasionally but for the last month it has gone down to 70?

Once again thanks in advance to all that reply.

Mick

[FROSTYBALLS]

Lower temperatures adversely affect fuel consumption.

[Gerg]

I'm assuming that this is temperature related, and nothing else has changed.

In the colder weather:-

When in stop/start traffic the engine will shed heat faster in the cooler air of winter, the engine has to run on for longer between shutdowns to maintain the engine temperature and catalyst at their pre-determined working temperatures (the cat. core won't work properly below about 500 C, I understand). Not so much of an issue on faster roads.

The engine will also turn on to service the car (cabin) heater, if it is set at a temperature that 'normal' engine operation can't maintain whilst powering the car.  So there are definite petrol savings in winter by turning the heater down, and turning the heated seats on.  Or wearing a coat.

The engine and transmission oils will be marginally thicker when cold, so more drag.

The gap between ambient temperature and engine working temperature is greater, so the warm-up phase is extended. From a cold start, an engine priority is to get the catalyst warm as quickly as possible to reduce emissions, one of the techniques for achieving this is to adjust the car's engine timing to intentionally send unburned fuel to hit the cat., where it heats it up.  But the MPG suffers.

At the other end of the scale(!), the longer nights and wetter weather that go with this time of year, mean that your headlights and wipers will be on more, consuming power, and driving through surface water will involve slightly more effort! 

Don't overlook the fact that as your MPG numbers increase, the actual volume of fuel you are saving for a given MPG increase goes down.  This can effect your judgment of what is happening.

Looking at the same thing the other way - 50 mpg lowering to 40 mpg is a (slightly) bigger volume increase in extra fuel used than 60 mpg lowering to 50 mpg etc.  As your MPG number gets higher, then small changes to the amount of fuel used make a bigger hit to the numbers!

I'm sure there are loads of others,  This is just to get you started.

[scar]

Comments are based on the latest model Yaris hybrid.

My wife has found her mpg has dropped recently as well. I expected this and the drop will increase when the temperatures fall even further. She has had the car from new and its 2 months old. It started off with 72 mpg, this is now 69.6mpg a small drop but indicative of the onset of colder weather.

I am still delighted with the mpg and performance. I would expect to see 65mpg when the winter chill sets in. Not too shabby !

My previous car was a Honda CRV petrol manual (now a RAV4 hybrid) that dropped 8-10% mpg in the colder weather. 

My wife had the corolla on test for a day, lovely car but she wanted the more compact Yaris for town driving.

 

[TonyHSD]

Hi, as mentioned cold weather is the major factor in fuel consumption and next that comes are wet roads, and wind and if you have winter tyres on or low tyres pressure. These combined together can negatively affect your fuel efficiency a lot. Nothing to worry about. 👍

[mrmick53]

Thanks all for all of your replies, interesting reading. Enjoy the rest of your weekend.

[AndrueC]

..and if you want snide remarks you only have to ask 😉

[bigblock]

On 11/1/2020 at 9:50 AM, mrmick53 said:

Hi again.

I do like posting on here, I find everyone very helpful and no snide remarks.

Could anyone explain why for the first couple of months that I had my Corolla I was getting 75 even 76 MPG occasionally but for the last month it has gone down to 70?

Once again thanks in advance to all that reply.

Mick

If your car is brand new then 70 mpg is excellent. You must have a very good understanding on hybrid driving skillls. As previously mentioned the cooler weather does have an effect on mpg. It may improve a little more as the engine beds in possibly.

[AndrueC]

It also depends on the kinds of journeys. Unlike conventional ICE vehicles hybrids do better when pottering around at low speed. One of our members is a taxi driver who was getting around 80 mpg in their day job then they took a long trip and I think only got about 60 mpg.

I remember once when I was caught in a jam on the A55 outside Abergele for nearly an hour - stop start where the top speed was barely walking pace. When I first reached the jam the car was showing something like 64 mpg after having driven about 160 miles at 60 mph. By the end of the jam it was showing a couple of mpg better. During the jam the car was using the Battery to move and switching the ICE on to recharge the Battery periodically. It makes sense because crawling at walking pace shouldn't require as much energy as cruising at 60 mph. However an ICE is very inefficient at low RPMs and a hybrid's Battery allows it to run the engine at a more efficient RPM thereby reducing the losses.

And model makes a difference. I have an Excel HB and the wider tyres are reckoned to cost 10% in fuel consumption. In summer I usually average close to 70 but in winter it can drop below 60.