300TE Poor fuel economy - PeachParts Mercedes-Benz Forum

ps2cho · #1 06-14-2011, 11:08 AM

Time to tackle it again...
This has been an ongoing issue since I have bought the car. I've kept track of all mileage and the average I get around town+freeway is 15-16mpg. On long trips between states, I get 19-21mpg.
Bought car 2006 @ 66k, I'm now at 107k

Spark plugs are OE H9DC0
New wires, rotor, cap, ovp, (used) coil
New o2 sensor, Duty cycle is closed loop 50%
New injectors + seals
No vacuum leaks of any kind all hoses replaced
Rebuilt Fuel distributor + EHA
All filters and fluids
No fuel smells or any sort of fluid loss.
Head has been rebuilt.

About the ONLY item I have not replaced (although checked volts) is the airflow potentiometer....Voltage came out to spec.
I guess also the idle control valve?

I plan to flow test the fuel system to make sure that comes to spec, but I can't imagine its bad since I've replaced everything including the distrib!

Any other ideas or suggestions?

I KNOW I should be doing better than this. I would be much more content if I was getting ~20mpg average and I believe I should be.

tjts1 · #2 06-14-2011, 11:13 AM

3500lb car with no lock up TQ and mechanical fuel injection. Sounds about right.

ps2cho · #3 06-14-2011, 02:17 PM

Quote:

Originally Posted by tjts1

3500lb car with no lock up TQ and mechanical fuel injection. Sounds about right.

From what I read from other members, they get around 20mpg and up to 25/26 on long freeway runs. Unless they are grossly overexaggurating, I see a problem somewhere.

My 260E gets about 21mpg avg regardless of how I drive. I accept that as reasonable, but I don't see a wagon losing 6mpg compared to it....The 2.6 vs 3.0L is offset by the rear-end ratio too...

I average roughly about 240mi to a tank before light clicks on. My 260E gets about 320mi before the light clicks on.

ps2cho · #4 06-25-2011, 01:00 PM

bump....

Also I notice once in a while the car will surge at idle around 300-400rpm and I can see the economy gauge swing like crazy. Something is going on here.

lkchris · #5 06-25-2011, 01:07 PM

300TE has lower axle ratio than 300E, so it's not just the aero and weight that make fuel economy different from sedan.

The W124 is the last of the "dinosaur" E-class. A nice W210 wagon with the new V6 and the 5-speed transmission will turn maybe 2700 rpm at 75 mph versus the 3500 rpm yours turns. The L-Jetronic is better than K-Jetronic, too, and it's a lot more efficient engine.

duxthe1 · #6 06-25-2011, 01:51 PM

FWIW, those #s are pretty close to what I get in the 4-Matic wagon unless I really pull the fuel out of it. Even then I've only gotten a maximum of 3mpg avg over the baseline through 1 tank. Have you peeked under the car to see what ratio diff you have? My 4-M has 3.29s.

ashedd · #7 06-25-2011, 02:42 PM

Quote:

Originally Posted by ps2cho

From what I read from other members, they get around 20mpg and up to 25/26 on long freeway runs.

Umm.... no. I don't see those kinds of numbers. I get 22 on the highway, down hill. roughly 18 in the city. The wagons seem to push a lot of air.

Hit Man X · #8 06-25-2011, 03:02 PM

FWIW my 300SEL just gave me 15.4mpg last fuel up... combined. I usually drive it 65mph freeway at the most. I have hit 20-21mpg freeway only before, but this is just driving around 65mph. City only is pretty abysmal, I think I have kicked back 11-13mpg with the A/C on.

Same motor, similar gearing (3.46:1), similar weight. This car screams to have a five speed manual for the extra efficiency in lower gears, no stupid second gear starts, and overdrive. Too bad we never received that here.

Your economy is fine. Oh I have been running 87 in this car for about 18 months with no ill effects.

ashedd · #9 06-25-2011, 08:32 PM

Quote:

Originally Posted by Hit Man X

Same motor, similar gearing (3.46:1), similar weight. This car screams to have a five speed manual for the extra efficiency in lower gears, no stupid second gear starts, and overdrive. Too bad we never received that here.

I keep getting talked out of swapping this 5 spd stuff into my TE.

ps2cho · #10 06-25-2011, 08:44 PM

Quote:

Originally Posted by duxthe1

FWIW, those #s are pretty close to what I get in the 4-Matic wagon unless I really pull the fuel out of it. Even then I've only gotten a maximum of 3mpg avg over the baseline through 1 tank. Have you peeked under the car to see what ratio diff you have? My 4-M has 3.29s.

Where is the diff ratio stamped on it?

So these people claiming over 25mpg are BS'n or not calculating correctly?

sptt · #11 06-25-2011, 09:57 PM

I'm lucky to get 21 MPG highway. '91 300E. Different engine now, same result. Everything is now new in it. Don't see how it can get any better without a 5th gear on the freeway. That car is heavy! I get about 315 miles to the tankful with about 80% highway driving. When I refill, about 15 gallons.

tjts1 · #12 06-25-2011, 10:01 PM

Quote:

Originally Posted by ashedd

I keep getting talked out of swapping this 5 spd stuff into my TE.

Why? Thats the first thing I'm going to do when I find the right 300te or E320 wagon. I already have all the parts for the swap in my 190e 2.6. Part out the rest of this car. Manual plus EFI conversion and it should see high 20s in a 300te. I bet theres a lot of useless weight I can drop out of the wagon. I removed 100lb from my 2.6 and I still have full interior, AC stereo etc.

Quote:

Originally Posted by lkchris

A nice W210 wagon with the new V6 and the 5-speed transmission will turn maybe 2700 rpm at 75 mph versus the 3500 rpm yours turns. The L-Jetronic is better than K-Jetronic, too, and it's a lot more efficient engine.

I drool over those rare W210 wagons every once in a while but then I look at the headlights and think there is no way in hell I could drive that every day. W124 wagon looks so much more classy.

This + EFI (factory or MSQ) and 5 speed manual = perfect car for me. LHD of course

ashedd · #13 06-26-2011, 11:32 AM

I would do the swap for a m104, just not sure about the m103. Plus, I would have to figure out the flywheel. The swap I did on my 300d was straight forward, no index marks. I have a 190e 2.3(?) flywheel, I just don't think it would work. Other than that I have all the other stuff, I got two of everything when I was at the yard one day.

ashedd · #14 06-26-2011, 11:34 AM

Quote:

Originally Posted by ps2cho

Where is the diff ratio stamped on it?

So these people claiming over 25mpg are BS'n or not calculating correctly?

http://www.w124performance.com/docs/mb/other/differentials.pdf

Perhaps one could achieve 25 mpg with an m104.

tjts1 · #15 06-26-2011, 11:58 AM

Quote:

Originally Posted by ashedd

I would do the swap for a m104, just not sure about the m103. Plus, I would have to figure out the flywheel. The swap I did on my 300d was straight forward, no index marks. I have a 190e 2.3(?) flywheel, I just don't think it would work. Other than that I have all the other stuff, I got two of everything when I was at the yard one day.

You'll need a 2.6 flywheel with the 3 timing windows. The later 2.3 flywheel has 2 timing windows and none on the early ones. Its pretty straight forward after that. The pedal box, shiftier, linkage are all the same. The drive shaft is almost the right length.