Morning guys,

Thought I'd just throw another question out there to you all. I've had my 2020 Focus Estate 1.0 MHEV 155 now for the last month, and would be interested to hear what fuel efficiency/fuel tank range people tend to get with their vehicles, especially other hybrid owners.

I've noticed fuel efficiency in my car is acceptable, but as soon as I put the fans on for ventilation, the mpg takes a hit, with the AC activated, the range of the tank then drops off significantly, to the point it makes the car quite uneconomical. You can almost see the counter dropping when sat in traffic etc. For a 10mile journey once, the fuel counter lost 30miles with AC on a gentle blower speed, the outside temp being a balmy 20 degrees.

Just seeing if anyone else has encountered such a drop with their cars? I've tried eco mode and that does actually seem to improve fuel economy etc, anyone else drive regularly in eco mode to improve mpg/range?

I didn't keep mine long enough to get through a tankful, but they are so frugal at idle that using the AC in traffic does increase the fuel consumption considerably.

My non-Ford has a display to show how much fuel is being used by things like AC or heated seats.  It's more than most people think.  Though I also find many drivers don't consider an idling engine to be using any fuel at all which seems very odd to me!  The same people that moan about a 9w LED bulb left on in the house are happy to sit in an idling car for half an hour...  

The other problem with using AC is that the radiator fan is always cooling the engine, so it struggles to get up to temperature, further increasing the fuel consumption.

AC really isn't to be used for short journeys or stop start traffic unless you're happy to accept the economy hit for it.

Hi Luke,

On my 125 hp mild hybrid I get the following (in litres)

Idling no AC about 0.4 l/h 

Idling with AC about 0.9 l/h in mild weather 20-27 deg Celsius outside

Idling with AC about 1.1 l/h in hot weather 35-40 deg Celsius outside (radiator fan is on full speed in these conditions)

City driving in hot weather with AC on I believe the worst ever was around 8 l/100km (so that is 35 mpg UK according to online converters)

On open road I have never exceeded 6 l/100 km (47 ish mpg) but this is again the worst. Normally my car takes about 5.2-5.5 l/100km with AC on (54 mpg - 51 mpg)

I am quite gentle with the car and I don't push it. However, my cruising rpms are always around or above 2800, so maybe consumption changes if I keep it at other rpms. But somehow I found that this is the sweet spot as in 5th gear I am cruising at about 110 km/h at 2800 rpm and in 6th gear I am cruising at around 130 km/h at 2800 rpm so that is how I ended up driving like this 😄

 

Much appreciated for the feedback guys. I haven't recalled my previous vehicles being so thirsty with AC on, but maybe I just hadn't really been paying much attention to them. 

For most of the 30 or so years I've had cars with aircon/climate control, I've subscribed to the view that the benefits of leaving it on permanently to keep seals lubricated and avoid re-gassing, outweighs the fuel consumption penalty (if any - I can't say I've particularly noticed).

Does MHEV change the situation? I'd be interested to hear more on this from other MHEV owners.

I don't really understand that.  We've had a few of the same cars, but I did notice an MPG hit when using AC.  

I think it's the engine size that makes the most difference in this case.  If you've got a large conventional petrol engine, the AC percentage increase is less noticeable because it already takes a large amount of fuel to keep that idling at stoich.  On a 1.0, especially with stratified injection, it can keep ticking over using very little fuel.  But add the drag of the AC pump and the drag on the alternator from the rad fan, and it's added as much load to the engine as if you were creeping in traffic while not actually moving anywhere.

I would say it's worth trying a tankful with the AC switched off to see what the difference is.  I am genuinely interested to know whether modern cars are still the same.  The most modern car I've done that test with was a 2012.