XC70 D5 poor MPG

[lotuscorty]

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.

[apersson850]

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).

[lotuscorty]

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.

[lotuscorty]

Originally Posted by apersson850

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).

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

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

[volvoski]

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.

[lotuscorty]

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.

[taz]

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.

[Gazdkw]

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

Not sure If mine has the swirl flap or not

[Kev0607]

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.

[lotuscorty]

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??