SEC1939

I just purchased a used 2005 E320 CDI wih 15k miles. I have made two -three long hwy trips and averaged 32-33 mpg after reset & doing actual pump refil calculation. Speed range 65-75 mph in midwest

Cruise on & off no difference. tail wind or not. Tire pressure is fine. I am hoping to get what others do high 30's even 40 mpg's

Any ideas? I do not want to hear the dealer say this is normal.

Thanks In advance

DslBnz

I think that kind of mileage takes real commitment. A real light foot. Take Jeremy Clarkson's recent run in the Audi A8 diesel for example. He managed to get 32 mpg or so, and he was driving purely for economy, using inertia on hills to help him gain speed. That was in a 4.2 liter V8 twin turbo diesel, however. Decrease the displacement to the 320 CDI level, and you would get a car that got 39 - 40 mpg.

Besides that, everybody in Europe averages just about that (32 mpg) in every year CDI from 1999 - 2005. I never understood why, exactly the American versions are touted as getting better than their highway EPA ratings when their European counterparts can't even come close. They must be driving like Old Lady Fritz.

The combined avererage is IN FACT 32 mpg. So you should see an average of 32 mpg. Sometimes above, sometimes below. Do not forget, you're pulling a 4K lb + car!

I've never driven one for an extended interval, but I know with a diesel most of the mileage comes from fuel quality. Which is highly variable in this country.

DslBnz

Take RunInColorado's post for example. He never took the car over 55 mph! The ideal cruising speed for economy. He averaged 37.8 mpg, admittedly with the climate control on and the engine still green.

https://mbworld.org/forums/diesel-forum/142349-first-trip-06-e320-cdi.html

That seems to be the norm.

SEC1939

I did read about winter vs summer blend & that summer blend would yeild better results. Perhaps my local guy has winter fuel still?

I assume truck stops would have the freshest fuel. I know all fuel comes from the same source with different additives blended at time of shipment but is there a brand that has the best additives?

Has anyone over inflated tires by a pound or two? I am at recommended 28 psi fronts 30 rear

Thanks

RunInColorado

I would assume that 32-33 would be the norm at 65-75. The 37.8mpg that I posted a while ago was unrealistic unless you plan to only do 55mph and really focus on trying to get the best possible economy out of the car. Remember the hybrid chant: Perfect planning leads to perfect passing. Having driven the car around the city, unless you drive like a grandmother in a buick the fuel economy drops very quickly (perhaps I am rather lead footed). The type of terrain also makes a huge different. I took my C230 to VA on 77 and on the interstate averaged 24mpg (low for me doing the speed limit). Comming back on the same road and nearly identical conditions resulted in 32 mpg. I have heard some people over inflating the tires by a couple of psi to get a couple more mpg. However, I personally think its better to keep the tires inflated per MB specs.

jimbo1mcm

With tire pressure 32f 35r, I get about 33 mpg in my 05 CDI with 14,000 miles on the engine. That is highway driving at about 74mph. I think you will nudge it up a bit with summer fuel, but not much. You are not going to get high 30's or 40mpg in this car. Relax and enjoy.

H-townbenzoboy

I don't what brands use additives, but I do know for sure that truck stops indeed have the freshest fuel. With so many big rigs coming in, there's a high turnover rate. Compared to your regular gas station with diesel pumps, who knows how many diesels come in on a regular basis, it's probably "stale", and has water in it, and possibly fungus (commonly and mistakenly called algae.)

cyclerider

How many miles were your long highway trips, and what was the outside temperature? My car seems to return better MPG when it is hot outside than when it is cold and wet.

lkchris

Your car is EPA rated at 37 highway.

EVERY Mercedes publication and EVERONE else says "you'll probably get less."

There is talk of EPA making its testing more realistic.

Best we've ever seen on our '06 CDI is 34 on long highway trips, and that's just on multifunction display.

NO car rated EPA 37 highway is going to get 40.

TPAbnz

32 - 34 highway mpg for me too. Great power and enjoy every minute of it!

cyclerider

On my last trip to Arizona, I did nearly 3000 miles of highway driving between 70 and 80 MPH with the A/C on and using cruise control 90% of the time and got 37.72 MPG. This was calculated by the total of my fuel receipts, not the computer in the car.

The onboard computer had my average at 35.6 MPG and my average speed for the entire trip at 61 MPH.

CE750

Oh yeah?

I averaged 66mph for 12 minutes or so, and the OAT was about 100 degrees F, and an elevation of 1100' and I got 40.0mpg.. And that was before the engine was properly broken in, I expect to exceed that now. The I-17 that I traveled on was more or less flat for that 15 mile stretch.

Variables are.. I use Redline Additive WITH EVERY TANK.. 1/4 bottle, and I have RennTech tuning with about 10% more power.