stickygreen

My CDI was only able to muster about 28.5mpg on a 100 mile drive yesterday, most of which was spent at 90 mph. Even when traveling around 70mph, I've barely been able to break 33 mpg on the highway. Seems like others are getting better mileage out of their CDI's. Does California have crappy diesel fuel too?

Raj
'97 e320
'05 designo e320 cdi
'85 535i

MBE55AMG

I think the 90 mph is to blame.

Green E-300 DT

Seems that you're not getting very good mileage indeed .

Are you tires air up properly?

Do you wind it up all the time, or allow the low speed torque to do all the work?

How about second gear starts?
I've found that using second gear to start up from rest in my older 300 DT helps here.
There is no need to wind 'em up. Make that low speed torque work for you.

Don't expect very good mileage at 90 mph!

As far as California fuel is concerned, we have the best in the country.
What brand are you using?

Arco will usually yield a trifle less, but it is really hard to record any difference.

Is this tank average mileage or off-of-the-computer?
With other vehicles over the years, I have discovered that computer
mileages are usually not as accurate as actual tank mileage.

Best to take the averages of several full tanks.
100 mile tests are not at all accurate.

Do you usually fuel up at the same pump with the Designo parked in the same position?

Many are inclined to "stetch" the truth if you get my drift? :p

These are little considerations but can and do make a difference.

Do you really fill it up completely and take the extra several minutes to make
sure that all the bubbles are gone and that the tank is really full each time?

Please keep us posted.

Spartan

Yup, it's lousy mileage alright!

OBVIOUSLY the wife is not pushing hard enough.....

cyclerider

I made a trip to Arizona last month, and saved all of my fuel receipts. In almost 3000 miles of highway driving between 70 and 80 MPH with the A/C on and using cruise control 90% of the time, I got 37.72 MPG.

The onboard computer had calculted my average speed at 61 MPH (I had a small amount of city driving in Phoenix) and showed only 35.6 MPG.

I was pleased to get almost 38 MPG, but was surprised that the onboard computer missed the mark by over 2 MPG.

stickygreen

yup...
Use the torque for the most part on the highway. I only wind it up if necessary when passing.
Nope, always leave it in "S" mode. I'm not so sure that 2nd gear starts are good for that clutch pack.
Always Shell or Chevron. I dont always use the same gas station, and have never thought to use the same pump. But my mileage readings are based on the OBC, not calculated mileage. I had figured that by now, they would have figured out a way to display an accurate reading on the OBC.

I'll due a more "scientific" mileage test next time around and post results. If my OBC reads similar to cyclerider's, then I might be getting 30+ mpg @ 90mph!

Raj
'97 e320
'05 designo e320 cdi
'85 535i

marcos

I think that the gearing is slightly different in the USA compared to Europe but I always manage to get 31 - 33 when cruising at around 90 mph, including any stop starts. Through France I set cruise at 145 for nearly 50 miles and got 24 mpg which I thought was pretty cool.

TPAbnz

Do you happen to know what your cetane numbers are?

kort677

your gallons are larger than ours

Spartan

In the last 1.25 years, I had TWO diesels E-class that are EXACTLY the same. Here is what I got from both of them in the last year+ and 14,000 miles.

City-Saburban....25-27 MPG,

Highway.....35-36 MPG at 75 MPH. 42MPG at 60MPH

Note: All figures are US mpg.

Note 2: First car had 11,000 miles and second 3,000 miles so figures should improve by a MPG or two after 20,000 miles or so.

Note 3: My highway miles are always done the same way. Set the car at 75 MPH and just sit back, relax and read the newspaper, enjoy a cappuccino. Occasional, I peek over the paper to make some course corrections or pass another truck.

E55AMG99

Automatics do have clutches but they are not used when the vehicle is starting out like a manual. They are to minimize shock during gear engagement. The "slippage" during accelleration from a stop is provided by the torque converter which does not have any wear items. So, starting out in second gear will reduce clutch pack wear since there is one less shift.

Back to your low mileage problem. Reduce the speed and watch the mileage go up. My GMC 2500HD gets 18mph when I can keep it 65 or under but only 15.5 if I take it up to 75-80.

mbnj

You set your cruise control for 145 MPH in France?? What is the limit? I don't think I've ever been in a car going more than 110 let alone cruising at 145!

Spartan

He's mixing his miles with his kilometers.....the same way I mix sushi with beer......

145 kph = 90mph

mbnj

Thanks, Spartan. I wondered but since he was quoting MPG I figured he had his number consistent!

CE750

At 90 mph I can get about 33mpg... at 66mph I get 40mpg..

But then I have Renntech tuning, and that could play into it..

You should easily be getting the 37 highway at 65mph that EPA got.. I wonder if your California Diesel is low in Cetane? 40 is bare min, and 45 is ideal... I add Redline 85+ additive to every tank... besides adding to the lubricity of the diesel, it also boosts cetane by 4 points for a 1/2 bottle per tank.

marcos

No definately 145mph which equates to about 233 kph. Things are changing now with the French Police but on the Peage ( toll ) roads it used to be possible to overtake the Police at high speed and they wouldn't do a thing unless you were driving stupidly.

marc777

This is what my desiel achieved in France.

Thats an average of 75mph for 9 1/2 hours - average mpg (UK) 38mpg.

Marvellous.

Spartan

Within 5% of what I get with a new car. It should match as the car get's worn in.

As for the 9 1/2 hours....YIKES....don't you need a bladder brake? Or are you related to the cat family?

marc777

:p :p :p

The trip was 9 1/2 hours of driving and the average was 75mph - allowing for pee breaks, fuel, traffic jams, tolls etc etc

Marc

Fastbuck

An avg of 75mph is good going Marc. Good effort!!! Well done goes to the CDI as well for the 38mpg, truely outstanding.

CE750

This is a Old, I know.. but I'm reposting it here for the benefit of the thread..

khaug

This is what my desiel achieved in France.

Thats an average of 75mph for 9 1/2 hours - average mpg (UK) 38mpg.

Marvellous.

Since you're in the UK, I assume those are Imperial gallons. A US gallon equals .833 Imperial gallons, so your 38 mpg would be 31.6 miles per US gallon.

Our CDI has done 38 calculated mpg on its best tank of fuel (Lansing, MI to USAF museum in Dayton, OH and return) and 32 mpg overall. The Goodyear 18" tires now on the car have degraded the mileage by about 8%, however, so my days of great mileage are over.

mbnj

I must be the only one totally impressed that he drives with his cruise control set at 145mph

Green E-300 DT

Not exactly, although if I were to spend more time searching, I might be able to give you exact numbers.

C A R B has their requirements, but there are various brands that exceed that minimum I'm sure.

I would say that there are many brands that are in the high 40s up to the low 50's.