64lusso

Hi Folks,
I am new here and am currently driving my Mom's 2006 E 320 CDI. My sister and I helped her buy it in late 2005 and she gave up driving earlier this year, it had a few small issues which we have attended to but as of today it has a little over 17,000 miles on it! So we have a 10 year old Mercedes that is barely broken in yet.
This car is the I6 pre Blutec and was made prior to the low sulfur fuel regulations going into effect. I have taken it on a few trips and was a little surprised that I was only able to average 35mpg on the interstates according to the cars computer.
I am not interested in high performance tuning but wonder if there is something that I could or should do to make it perform better with today's fuels?
Thanks in advance for your help,
Jay

DennisG01

Can you find the gov't specs on what it was "supposed" to be? How does it compare? However, that sounds about right - or at least what I would expect to see on that car. Also, you need to hand calculate it - it's more accurate. For what it's worth my dash gauge is about 2mpg lower than what I really get on the highway.

boardboy330

You can tune it for around $500 and it should net you 3mpg minimum and about 5mpg avg increase. We drive ours 50K miles a year so it is a no brainer. For you, it might be different.

64lusso

According to the window sticker that came with this car it was rated at 37 highway and 27 city. I don't drive with a heavy foot and haven't seen either figure close to that. Most of my current driving I would classify as suburban so it would be hard to do an accurate hand calculation unless I take it on another trip given it will go 600 plus miles on a tankful!
As far as tuning it for current fuel, I know I couldn't do it but if I decide to keep the car I would definitely like to do that. How would I go about having it done?
Jay

Plutoe

If you ever decide to sell the car-----let me know

LAS_Bluetec

The computer can be off. Check miles driven against gallons of fuel used.

DennisG01

Well, in comparison to the window sticker, you're only 2mpg off. That sounds pretty much in the right ballpark to me? Driving style, weight in the car, ambient conditions... all affect mileage. Plus, did you see the part where I mentioned my dash gauge is typically 2mpg shy of what I really get? If that holds true, it puts you right back to what the window sticker says.

What speeds do you drive on the highway? Best mileage, from my experience, is going to be 55-60mph.

I really don't think there's anything wrong, based on the information provided. It sounds like it's doing exactly as it was designed.

Always hand calculate - whether highway or city.

Also, just for giggles, I looked at Edmunds for your year... they list 23/33 mpg?

shedkept

Ours has 125,000 on it. Gets 41-42 on the interstate and averages 32 regularly.

sand8

The engine has not fully broken in yet. Normal city driving will get around 28-33 mpg. Highway can be 35-40 mpg if the car mileage is over 50k.