Shell vs Super market petrol !!

[Paddy]

I'm not a tester but a bit anal about recording stuff - maybe I should become one.

Old car got better petrol consumption wise over the 75K miles and 8 years I had it - started at 37 MPG and ended at about 43 MPG - averaged 42 MPG over the 75K miles. Small petrol engined warm (ish) buzzbox.

Current similar car has only done 4.5K but started at 41 MPG, dipped to 37 MPG over the winter and is now doing about 41 MPG again.

So, in answer to the OP, cold weather may well account for some of those 80 extra miles.
School holidays help as well and we've just had easter - less traffic so fewer holdups.
And the heart attack induced by paying for a visit to the petrol pump may have resulted in more economical driving!

HTH

Cold air or cold damp air gives a better performance and improves economy. With Diesel you need hot fuel, cold damp air. Think about it.

[ctdctd]

Cold air or cold damp air gives a better performance and improves economy. With Diesel you need hot fuel, cold damp air. Think about it.

No it does not - or at least as part of the whole car driving package.

I have 10+ years of fuel economy records showing winter is worse.

[Paddy]

No it does not - or at least as part of the whole car driving package.

I have 10+ years of fuel economy records showing winter is worse.

What I said is basic physics of how engines perform. Cold damp air compresses more than warm air. On hot days, engine performance decreases. It is best tested on a long straight road without traffic.

In winter you are getting less MPG because of other factors, you are probably changing gear more, using the car on short journeys instead of walking.

[tranceporter]

Nope. It's because the fuel vaporises in summer leading to less mpg

[Normie]

Would one of these gizmos help track fuel effeciency?

OBDII Bluetooth Car Diagnostic Cable - Black + Blue + Orange (DC 12V) - Free Shipping - DealExtreme

Along with a copy of Torque or something similar on your phone/Ipad/laptop.

[stek]

Shell vs Super market petrol !!

Would one of these gizmos help track fuel effeciency?

OBDII Bluetooth Car Diagnostic Cable - Black + Blue + Orange (DC 12V) - Free Shipping - DealExtreme

Along with a copy of Torque or something similar on your phone/Ipad/laptop.

You can get wifi connections now!

[b0redom]

In winter you are getting less MPG because of other factors, you are probably changing gear more, using the car on short journeys instead of walking.

Plus using the heating more, lights, heated rear windscreen, heated seats? All that requires more power = running the engine at slightly higher revs = less MPG.

[Paddy]

Plus using the heating more, lights, heated rear windscreen, heated seats? All that requires more power = running the engine at slightly higher revs = less MPG.

That’s why manufactures disconnect the alternator when they do the MPG figures

[Troll]

That’s why manufactures disconnect the alternator when they do the MPG figures

I thought we were going 24volt systems on cars so things like power steering & AC pumps could be run off battery rather than driven off the engines

[VectraMan]

What I said is basic physics of how engines perform. Cold damp air compresses more than warm air. On hot days, engine performance decreases. It is best tested on a long straight road without traffic.

Why would the amount it compresses make a difference?

Cool air is denser - i.e. has more oxygen molecules. All modern cars have sensors to detect the air pressure or temperature going into the engine and can squirt in more fuel to keep the ratio the same. More fuel + more air = more power. Whether that produces better MPG too I'm not sure.

The real question is why does a 2 litre car use more fuel trundling along slowly than a 1 litre car? If they could just solve that, then we could all have twin-turbo 5 litre V8s and still get 60mpg on a trip to the shops.