2004 E320 CDi - Running Temperature & mpg

[Razoo]

2004 E320 CDi (3.2 litre, straight-six)

I have noticed during this period of very cold weather that my mpg has dropped by about 10% on my work journey. I used to average 40-41mpg but, for the past couple of weeks, I have only been getting 36 to 37mpg.

The car also seems to take a long time to warm up, so I have started watching the engine temperature gauge closely.

This morning the ambient temperature was -1.5 degrees C. Six miles into my work journey, my engine temperature gauge was showing 60 degrees C. The highest it got to on the whole 22 mile journey was 80 degrees C, although it seemed to keep cycling up to 80 degrees and then dropping back to 75 degrees, and then rising to 80 degrees again.

I estimate that once warmed up, the engine temperature averaged around 78 degrees C (assuming of course, that the temperature gauge is accurate).

I guess 80 degrees C is about right as a running temperature, but I'm wondering if replacing the thermostat might give me a quicker warm-up period. Any thoughts, anyone?

Could someone tell me the correct thermostat and confirm the ideal running temperature for my E320 CDi?

Thanks,

Razoo

 

[psmart]

There have been several threads running on this subject this winter and basically its normal. Winter months are colder, meaning denser air, which whilst beneficial to the engine, the car has to push through greater air resistance. Also, as its colder, and as diesel engines are more efficient, less heat is created by the engine and more wasted in cooling by ambient air and the radiator. If your not doing high speeds or thrashing the car, you can block off part of the radiator (take special care not to block off the air-con, intercooler or oil-cooler).

As an example, its -10'c here and has been below 0 for last few weeks. Driving the C220cdi or the ML270cdi to work they never get above 60'c, in comparison, the petrol 500 is full temperature around half way to work.