XC70 D5 poor MPG
 

2010 XC70 geartronic 205 D5 currently reading 23 mpg on the OBC. Recently had a boost pipe fixed, drives well, no codes or issues, just drinking fuel. Granted mostly about town, but economy is worse than the old Xc90 I just replaced with this.

It has been suggested that changing the thermostat may help, but since it is costly to replace, is there anything I can check before doing this? What temp should it run at?
Anyone else had the same issues? Thanks

Has it been serviced recently? If not, that might be a good place to start with a new fuel filter, air filter etc.

I was going to suggest air filter and service. That said I don’t believe that alone could make that poor consumption.

What tyres are fitted to it? Certain types of tyre can effect MPG. Also it’s worth jacking up each corner and rotating the wheels to check you’ve not got a binding brake. I’ll assume you’re not driving round with a roof box on, but if you were that wouldn’t help MPG.

Has been serviced and made no difference, genuine parts too. Tyres are Pirellis and are not m&s or winter, however I don't believe tyres would make it that bad?
Thermostat argument seems the most plausable?
If the car is driven at all spirited it is very low 20's, although it hasn't had a good run of over 40 miles in a while

Most diesels engines are slower to warm up than petrol engines when under a light load, so your car might not hit full working temperature during short journeys. That'll hit MPG.

Having said that, I've also found that diesels very quickly hit working temperature if they're whizzing along at higher speeds.

It's also possible that your old XC90 got up to working temperature more quickly because it was a heavier car, and the engine was under a heavier load at all times.

(An early XC90 auto that I borrowed once had a very short first gear, which I suspect was needed in order to get that very heavy vehicle moving.)

If your thermostat is dodgy then I'd expect the car to either overheat or to take an age to reach full working temperature, even on a fast road.

So, what does the temperature gauge say?

Others members may offer a different perspective and, as ever, YMMV. (And it clearly does. :) )

Car seems to take a while to warm up, (heaters anyway when it's cold) anf it doesn't have a temp guage to see what it is doing. Anyone know what the operating temp is for the D5 205???

Not sure on the operating temp......but the cheapest way to find out is with one of these - EML327 OBD2 Bluetooth Adaptor and a app such as Torque on your phone. It'll give you the info you need for the stat opening/closing due to the temp readout.
Once connected you can see what the coolant temp is and how it rises and falls.

Vida Dice is the dogs...If you have a few quid to spare.....as it can do so much more.........worth it in my opinion though.

Hope this helps.................................I also have no temp gauge...:angry_smile:

They brought the temperature gauge back in later V70s, and I'm glad that they did. :)

I know the earlier D5 models had swirl flaps, I'm presuming yours does too? A broken link/connecting rod as an example could affect your mpg because the car isn't getting the right fuel/air mixture.

Have a look at the 7th picture in this thread. The plastic connecting rod, just near the yellow wiring in the picture can simply disconnect through wear & tear.

https://www.volvoforums.org.uk/showthread.php?t=275786

So, its had a service & hasn't made much of a difference. The tyres are a decent brand, what about the tyre pressures out of curiosity? I know it may sound trivial, but low pressure can effect fuel economy & its something that many don't bother to check. I'm not implying that you don't by any means, but its true.

However, a VIDA diagnostics readout might reveal the potential culprit & would probably be your best option to see if there's any fault codes storing in the system. Its a guessing game without that really.

As these cars age the message is that serious owners need to own their own VIDA/DiCE to quickly identify the causes of performance deterioration. Even if you had to buy a second hand laptop to run the program, the outlay is not likely to be much more that £100 for everything including a car charger so you do not have to worry about the battery state of the laptop.

The car has been on VIDA and there are no codes to suggest anything is wrong, the only historic one when an intercooler pipe was split. I will have to do some running and check temps etc. But ai don't know what temp is the normal running temp? I would assume about 90 like most cars??

Don't think my engine has the swirl flaps?? Going to run it today with diagnostics connected and see what temp it's sitting at. Anyone know what it should be?? Thanks.

90 sounds about right. Funnily enough I stuck my EM327 in this morning and connected via Torque app on my phone.
I didn't do a long run as such, but the temp rose to nigh on 90 then dropped slightly and rose again before dropping again and continued this throughout. Stop starts, pick up the paper,Tesco and a visit to my sister some 8 miles away.

Hopes this helps.

What you need to know is how long does it take to reach that operating temp.
I'm off work this week and come Tuesday will be going away for a couple of days......I'll post at what mileage I reach the operating temp and the time it took, speed, etc. as it all factors in....so does the outside temp.......

Euro 4 engines onwards have them as far as I know, so yours should too.

V70Zig Thanks for the info. If you could let me know how long it takes to reach operating temp that would be really helpful.
I ran it today but only for a few miles and it was nowhere near 90. I'll check it on a longer run. Thanks.

Kev0607 I'm not sure my engine has? On the older engine I am aware of where the flap lever is, however nothing on mine. The engine is a D5244t10

No swirl flaps on this engine

My cold start this morning -
Outside temp 11, coolant temp 11 before startup.
First 2.5 miles to get out of town 30 mph max. Then onto dual carriageway 60 mph.
Having covered 5.5 miles in 9 minutes the coolant reached 91 before dropping back to 87 - 88 - 89, 88 - 89 consistently for a further 6 miles.

My average consumption at opening was 27.9 according to the dash. Finally it's pretty flat round here.

Nothing in Vida re a swirl flap motor for yours.....there is for mine. So Olaf is probably right.

And today - same destination, but missed out the dual carriageway and went through the villages so a lot of speed bumps and 30 mph speed limit.

Outside temp 3, coolant temp 5.

So it took 6.6 miles and 17 minutes to reach temp, then acted as yesterday.

Just shows you that outside temp and speed come into play.

Hope this helps.

Ok, so did a short run today. Outside temp 6 car was 22 as had been run previously. Did about a 15 min run, short bit of town and then dual carriageway for about 8 miles and couple of miles of town again. Highest reading I got was 67, so comparing that, it would seem that the thermostat seems to be stuck open, so I guess that will be the next job to replace that!!
Thanks for all the help.

The main factor in thinking the thermostat is that when I was slowing from 70, etc. the temp would go down (although it was a cold wind) so next step change it and sew what happens.

Normal running temp is 88°C.
Due to free air flow in these engines, coasting for longer distance, like downhill for a kilometer, will reduce the temperature a few degrees, if it's cold outside.
To reach running temp in a reasonable time during winter (below zero), the diesel fueled auxiliary heater needs to run in parallel. Not sure that was fitted to UK cars, though.

My XC70 D5 AWD automatic can come as low as 6 l/100 km during long-distance driving at modest speeds (80-100 km/h).

The main factor in thinking the thermostat is that when I was slowing from 70, etc. the temp would go down (although it was a cold wind) so next step change it and sew what happens.

Well I am getting less than half the mpg you are getting!

Not sure if my car has an auxiliary heater though??

Our XC70 gives around 28/30 mpg around town. We get 40 on a 70 mph motorway run. We have noticed that when the car hasn’t had a run for a few weeks the mpg suffers. Give it a good clean out run and it improves 1/2 mpg again. It always raises its mpg after a service / oil change too.

Thanks. That's more what I would expect from it, seeing as my old XC90 did about the same. But low 20's about town is a bit extreme, would expect that more from a petrol model. A previous V70 D5 I had would do high 30's about town albeit manual gearbox on that.

I have the same problem on mine as its a Polestar model WITH the swirl flaps fitted & I ended up replacing these thinking this was why the car only averages 30-31mpg. It did improve it a little bit as I also cleaned all the black, gunky crap out of the EGR & connecting pipework too! Bust the link arm when refitting the flaps.....Damn! So had to go get a new one from The Stealership's. I've replaced the thermostat (can get this on its own for about £15.00 from Euro Car Parts). Piece of p*** to fit. So I'm at a loss on whats up as I can get about 42mpg at 60mph on a motorway/dual carriageway.

Mine averages around 29-32 around town and 40ish on a motorway run.

Not sure If mine has the swirl flap or not

Is it a big job to change the thermostat on the P3 D5’s? There’s not much coverage of it on YouTube from what I can find, just the older models seem to be shown.

Looks to me to be a fair bit of work. It is a complete unit round the back of the engine, egr and related gubbins need to be removed to access. Unless someone knows any different??

Yes, I’d be intrigued to know. Thermostat replacement on earlier P2 models looked a doddle. I’m not sure about the euro 4’s though (2008 onwards), but I can’t find any videos on the job in hand.

The later engines have a complete thermostat manifold which has to be replaced. The days of undoing three bolts, pulling out the old thermostat and replacing it with a cheaply bought new one are gone and it seems that Volvo do not expect you to routinely change the thermostat to ensure that it always is working at its best but to wait until it fails before getting involved with a lot of spannering.:sad_smile:

When you say ‘later engines’, what years do you mean? Or do you mean the P3 shape in general?

I only speak from what I have read on the forum while worrying about the high cost of changing the thermostat on my 2012 XC70 which I would do routinely if it wasn't for the expense and great difficulty in doing myself. I don't know exactly when the change in design happened but it seems to go back as far as 2009. See this for information: https://www.volvoforums.org.uk/showthread.php?t=197671

According to Vida replacement instructions it's a doddle on mine :teeth_smile:

But for lotuscorty it'll be a pain as yes the egr, throttle body, air box, battery etc have to be removed according to vida.........

The guy on here has some useful videos, sadly stat change isn't.....be cheeky and message him to do one....stat change that is.

Would you mind posting the Vida instructions? :regular_smile:

When searching for the thermostat for my Dad's V70 P3 D5 (57 plate), it brings up the attached image as being the correct part. It looks like the one that's a pain to change?

My Dad's car is the same as yours V70Zig (No Polestar though, standard 185bhp D5). Its six months older, but its the facelift shape. Does this look like the correct part?

It does look the same as mine, you can get Vida without the Dice from the bay for as little as £1.49 and run it on your pc or less than a tenner if you want the disks.
It's a pain to print them from my lappy, scan and then upload to here so as a quicky here are just the pics....the only special tool is a 19mm deep socket to remove the sensor. Just follow the rad top hose it's front left hidden by the engine cover.

Just to be clear, how do we know if it needs changing at all?

Its just a case of monitoring the coolant temp? I have a bluetooth reader attached to the car so it's pretty easy to read

D5 is just a badge denoting a 5 pot engine, there are engine variants for the D5 and might not be the same, putting the correct info into Vida should give you the right info.

I too have a bluetooth reader, because I don't have a temp gauge ! I have the torque and the car scanner apps on my phone to see actual temp.
From lotuscorty's posts it looks like his has unfortunately stuck in an open position which will fool the ecu into over fuelling.
Quickest way to to check without any apps or diagnostics connected is to start up from cold (overnight) and feel the top hose from rad to engine as it should remain a lot "cooler than the bottom hose" if it's getting warm after a couple or 3 min it's more than likely stuck open or partially open.

Welcome anybody's views on this post just in case I'm wrong....oh and there is a thanks button if I'm right...............