XC70 D5 poor MPG

[lotuscorty]

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

[Kev0607]

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

[XC90Mk1]

Originally Posted by Kev0607

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.

[IronJaw]

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.

[lotuscorty]

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

[Sotosound]

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. )

[lotuscorty]

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???

[V70Zig]

Originally Posted by lotuscorty

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...

[Sotosound]

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

[Kev0607]

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.