AC MPG Impact

Beefcake 4000 · Apr 13th, 2018, 10:06

I've been getting really poor mileage <25mpg from my V70 petrol, the aircon has been on auto since I got the car and never really though much more about it.

This morning on the way into work, flat level piece of motorway, car in cruise control at 60 mph with the instantaneous fuel read-out showing (I know this isn't lab conditions) and AC switched off. Fuel read out was 40ish +/- 0.5, then i hit the AC auto button and read out dropped to 33 ish.

I know there are all kinds of factors at play and it was only a very short test. I'll finish this tank with the AC on then do atleast another tank with the AC off (where possible) and compare.

Does anyone have any similar experience?

old onions · Apr 13th, 2018, 11:59

If your next test does show the same significant difference I will certainly be copying you in the future.

Every time i have tried switching the a/c off I get misting up of the windows and screen , so I have been somewhat reluctant to do it, but if my mpg improves as much as yours then that might be a price worth paying.

BTW my mpg is currently in the range of 28 mpg (fully laden with 4 kayaks on the roof and 4 paddlers all with lots of kit) to 34 mpg (solo running)

JRL · Apr 13th, 2018, 13:13

Maybe get the aircon tested and refilled if it needs it? The compressor might be having to come on and off continually due to a low level of refrigerant. I'm no expert on AC mind you!

big_yin · Apr 13th, 2018, 14:07

Quote:

Originally Posted by old onions

If your next test does show the same significant difference I will certainly be copying you in the future.

Every time i have tried switching the a/c off I get misting up of the windows and screen , so I have been somewhat reluctant to do it, but if my mpg improves as much as yours then that might be a price worth paying.

BTW my mpg is currently in the range of 28 mpg (fully laden with 4 kayaks on the roof and 4 paddlers all with lots of kit) to 34 mpg (solo running)

My air-con is currently not working as it needs to be refilled but don't suffer from misting up windows. How is your cabin filter ?
Any coolant loss ?
I was suffering from misting windows when a heater matrix was leaking on my P1 V70.

Brendan W · Apr 13th, 2018, 15:59

The rule of thumb for me is modern cars can maintain 60mph with around 20kW or less. A typical a/c compressor is capable of absorbing 3kW or more.

Dippydog · Apr 13th, 2018, 19:34

Up to a certain speed[possibly 40mph? but can't remember exactly]it is more economical to open a window than run the aircon.Above that speed the situation reverses and aircon becomes more economical than having a window open.They did used to say that running the aircon could make up to a 5% difference in fuel consumption.

oragex · Apr 14th, 2018, 19:49

Remember reading it ads 5-10% to the fuel consumption

The compressor pulley bearing does wear and may seize after 150K miles

Clan · Apr 14th, 2018, 20:57

Quote:

Originally Posted by Beefcake 4000

I've been getting really poor mileage <25mpg from my V70 petrol, the aircon has been on auto since I got the car and never really though much more about it.

This morning on the way into work, flat level piece of motorway, car in cruise control at 60 mph with the instantaneous fuel read-out showing (I know this isn't lab conditions) and AC switched off. Fuel read out was 40ish +/- 0.5, then i hit the AC auto button and read out dropped to 33 ish.

I know there are all kinds of factors at play and it was only a very short test. I'll finish this tank with the AC on then do atleast another tank with the AC off (where possible) and compare.

Does anyone have any similar experience?

on 4 separate journeys of 100 miles over 2 days on the same route about 10 years ago with a S60 it worked out AC was 3 mpg less economical .

newtonuk · Apr 15th, 2018, 08:13

On a regularly repeated 400 mile journey I can get 51-52mpg with AC off, but 48-49 with it on.

Beefcake 4000 · Apr 30th, 2018, 17:29

Highly unofficial, unscientific results are in. 40 litres of fuel, one tank with AC on Auto, one with AC off, similar driving journey and style etc.

with AC on Auto; 234 miles from 40 litres = ~26.3mpg
with AC switched off; 237 miles from 40 litres = feck all difference

Oh well, atleast I can be comfortable again.

Apr 13th, 2018, 10:06	#1
Beefcake 4000 New Member Last Online: May 4th, 2018 09:20 Join Date: Mar 2018 Location: Emsworth	AC MPG Impact I've been getting really poor mileage <25mpg from my V70 petrol, the aircon has been on auto since I got the car and never really though much more about it. This morning on the way into work, flat level piece of motorway, car in cruise control at 60 mph with the instantaneous fuel read-out showing (I know this isn't lab conditions) and AC switched off. Fuel read out was 40ish +/- 0.5, then i hit the AC auto button and read out dropped to 33 ish. I know there are all kinds of factors at play and it was only a very short test. I'll finish this tank with the AC on then do atleast another tank with the AC off (where possible) and compare. Does anyone have any similar experience?

Apr 13th, 2018, 11:59	#2
old onions Member Last Online: Sep 2nd, 2023 16:06 Join Date: May 2015 Location: Greenwich, London	A/C effect on fuel consumption If your next test does show the same significant difference I will certainly be copying you in the future. Every time i have tried switching the a/c off I get misting up of the windows and screen , so I have been somewhat reluctant to do it, but if my mpg improves as much as yours then that might be a price worth paying. BTW my mpg is currently in the range of 28 mpg (fully laden with 4 kayaks on the roof and 4 paddlers all with lots of kit) to 34 mpg (solo running) __________________ Andy G 2006 V70 SE 2.4 Manual Last edited by old onions; Apr 13th, 2018 at 12:00. Reason: poor proof reading

Apr 13th, 2018, 13:13	#3
JRL Master Member Last Online: Aug 25th, 2022 16:37 Join Date: Jul 2013 Location: Derry	Maybe get the aircon tested and refilled if it needs it? The compressor might be having to come on and off continually due to a low level of refrigerant. I'm no expert on AC mind you! __________________ 2008 S60 D5 SE LUX

Apr 14th, 2018, 19:49	#7
oragex Premier Member Last Online: Jul 26th, 2021 21:24 Join Date: Jun 2013 Location: Coldnada	Remember reading it ads 5-10% to the fuel consumption The compressor pulley bearing does wear and may seize after 150K miles __________________ Several Volvo Repair Videos https://www.youtube.com/playlist?lis...ECTts0FSVSOT_c

Apr 13th, 2018, 15:59	#5
Brendan W Premier Member Last Online: Apr 2nd, 2024 19:50 Join Date: Dec 2007 Location: Wexford	The rule of thumb for me is modern cars can maintain 60mph with around 20kW or less. A typical a/c compressor is capable of absorbing 3kW or more.

Apr 13th, 2018, 19:34	#6
Dippydog Premier Member Last Online: Apr 25th, 2024 17:55 Join Date: Jun 2016 Location: S****horpe	Up to a certain speed[possibly 40mph? but can't remember exactly]it is more economical to open a window than run the aircon.Above that speed the situation reverses and aircon becomes more economical than having a window open.They did used to say that running the aircon could make up to a 5% difference in fuel consumption.

Apr 15th, 2018, 08:13	#9
newtonuk Junior Member Last Online: Oct 25th, 2023 14:33 Join Date: Feb 2012 Location: Wakefield	On a regularly repeated 400 mile journey I can get 51-52mpg with AC off, but 48-49 with it on.

Apr 30th, 2018, 17:29	#10
Beefcake 4000 New Member Last Online: May 4th, 2018 09:20 Join Date: Mar 2018 Location: Emsworth	Highly unofficial, unscientific results are in. 40 litres of fuel, one tank with AC on Auto, one with AC off, similar driving journey and style etc. with AC on Auto; 234 miles from 40 litres = ~26.3mpg with AC switched off; 237 miles from 40 litres = feck all difference Oh well, atleast I can be comfortable again.

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