Erratic mpg.
 

Hello all, my 2013 S60 D4 163bhp 5 cyl has recently developed an intermittent fault. It used to deliver upwards of 50mpg with ease all the time, but now I'm struggling to get above 40mpg. Sometimes it runs fine still, but at other times it takes a big hit on the fuel consumption. When it's running fine it'll idle at 0.1gph, but when it's running bad it idles at 0.3-0.4gph. I know when the car is doing a dpf regeneration and its not that. With it being erratic I was thinking a sensor might be faulty, but I wouldn't know where to begin. Can anyone point me in the right direction of where to start looking/checking please? Thanks in advance of any replies.

How do you know that no dpf regeneration is going on?
I bet it is... your model can with the torque app read out the dpf temperature.
Or egr shutoff and throtle restriction
Try it :)
Also if regeneration is going on and your idling the regeneration is halted after a certain time idling activating again after some rpm/load

If there was overfueling at idle there would be higher rpm.... diesel engines
have massive air fuel ratios

When I say its erratic I mean sometimes from one set of traffic lights to another. One set of lights it'll be doing 0.1gph, the next it's 0.3-0.4gph and then back to 0.1gph. When a regen is going on the mpg takes ages to return to 99mpg when I take my foot off the accelerator, whereas when it's not it's shoots up to 99mpg rapidly. There's definitely a fault somewhere other than a simple regeneration. Thanks for the reply 5cylinder. I'm thinking of buying a vida/dice to see if it'll help get to the bottom of this.

I've got the torque app already, I'll check out the temps and stuff. Been a while since I've used it and thought it was pretty rubbish, but I'll give it a try.

if you think the torque app is rubbish i dont think you will get along with vida it is comprehensive but quite difficult to use it takes a long time to be good with vida :regular_smile:

Ofcourse vida is much better for fuel corrections and sensor callibration etc
But torque is handy for obd2 faultcode use and some sensor readouts and daily use since the phone is already there in the car.... a laptop and dice is a bit bulky for daily simple readouts

i have both and torque is handy ,alarm settings , regeneration alarms and monitoring airmass tweaking during regeneration
And ofcourse quick faultcode readouts during acute problems on the way

Ofcourse vida is needed for most deeper problems , but those are much more rare

You can alter the readout from miles pro gallon to for example gallon/distance
Gives much more accurate readouts ...... with no regeneration and depressing pedal ther is fuel cutoff without regeneration WITH regeneration with pedal depressing there will be fuel usage

Even better with torque you can easily alarm and see when a regeneration takes place on your phone in the backround.

If there are no obvious obd2 codes (with torque) then further investigation with vida is needed if its not regenerating

Aircon use wil also impact idle fuel consumption/difference at the traffic lights in a massive way if its coupled or decoupled at idle!
One traffic light aircon decoupled compressor.... next it could be coupled and loading the engine
The indicator if the aircon is on is no way to know if the compressor is engaged or not..... if its off then you know its always off

You'll be better off with Car Scanner Elm Obd2 app, it shows DPF soot in grams in most Volvo engines.

Just select 2008+ profile for 5-cylinder engine, or 2014+VEA profile for 4-cyl VEA engines (where you get engine oil level in mm). DPF soot and other sensors are in All sensors menu.

Are you calculating the MPG properly, or relying on the dash display?