[leej320d]

I have recently bought a bmw E90 320D LCI. During the first few days, my car was doing 65mpg in the motorway doing 75-80mph. However I took it for a run this week, during 120 miles run, the temperature is averaging 82-83 C with maximum 85 C.
I am base in UK, the outside temperature is around 1-2 C during my journey. the fuel consumption has been around 55 MPG on motorway at the moment.

Could it be the problem with thermostat ?

As seems the temperature should be around 90-92 ?

[Digitalize]

Where it's cold and the ambient is so low I'd not want to instantly say there's a fault, as the thermostats open at 88c, but I'd want to say the EGR thermostat has gone if there is a fault, it's too high to be the main one really.

The bigger influence will be that cold air is denser, more air in to the cylinder means more fuel to maintain the correct Air Fuel Ratio, so you'll be using more fuel in the cold weather. I'm struggling to get 40mpg in my early 320D at the moment.

[bishbosh]

An LCI will have the N47 engine, so no EGR thermostat. It's probably the cold weather, mine is struggling to get past 86 degrees but usually sees 91 in the summer.

[Digitalize]

Ah I didn't know the later engines dropped the EGR thermostat.

[hp88]

Also got the N47 engine in my 320d. Monitored the coolant temperature on the way home today as I thought my stat was on it's way out, after about 10 minutes I got a constant 90-91c.

[HighlandPete]

Originally Posted by leej320d

I have recently bought a bmw E90 320D LCI. During the first few days, my car was doing 65mpg in the motorway doing 75-80mph. However I took it for a run this week, during 120 miles run, the temperature is averaging 82-83 C with maximum 85 C.
I am base in UK, the outside temperature is around 1-2 C during my journey. the fuel consumption has been around 55 MPG on motorway at the moment.

Could it be the problem with thermostat ?

As seems the temperature should be around 90-92 ?

The thermostats don't normally just fail, they slowly deteriorate and open early. I'd suspect the thermostat is dropping back on its opening temperature. Cold ambient temperatures shouldn't change the ECT by much, (couple of degrees at most) once up to temperature and cruising along at speed.

When running my 330d, ECT slowly dropped back to low 80's over a few months. Replaced the main thermostat and then back to ~90C, even in sub zero winter temps.

[adammcf]

I did both thermostats in my 330D last weekend as the car was sitting in the 60s! All done now and its always in the 90s.