The MPG Thread to end all MPG Threads - FUELLY!

[andrewjtx]

Originally Posted by Delibes

-Fuel leak?
-Fuel filters?
-Bad glowplugs?
-Valve adjustment?
-Dragging calipers?
-Fuel sending unit?
-Bad injectors?
-Thermostat?
-IP timing?
-Bad fuel?
-Too fast?
-Tires?

Search on this forums and you will find a wealth of information!

Trust me, I have.

Glow plugs are great / nearly new with <15k on them
All filters are regularly checked/changed
Valve adj was done <15k ago
Compression is good
start up (even cold) is great
No smoke
Good power / throttle response
Engine sounds great
My 30-mile RT commute each day is on a mixed speed road ranging from 45mpg-65mph with a few lights interspersed.
Brakes aren't dragging

The only things at this point I have not exhausted are:
Injectors
IP timing
Replacing the cheap Michelins

I'm also coming off a bout with non-optimal oil and flushing in a few rounds of 15w40. The next OC at 171,500 I will be doing another valve adj, timing chain check and replacing a few leaking seals (turbo return, filter housing). If those items don't show some improvement, I'll be pulling the injectors for Monarch nozzles and pop/balance testing.

I just starting running the A/C again and that's where I'm getting the 18mpg.

[PhantomCadillac]

Maybe sticking odometer?? Keep a close look when it comes around on the .9 sometimes they stick there awhile and then release.

[andrewjtx]

Originally Posted by PhantomCadillac

Maybe sticking odometer?? Keep a close look when it comes around on the .9 sometimes they stick there awhile and then release.

You know. That's one thing I absolutely haven't checked. I also might borrow a GPS from a friend and verify.

Come to think about it, I was pulled over the other day (no ticket) for doing 70 when I swear I was doing 60.

Update: just ran out for lunch and the trip odometer rolls over smoothly.

[andrewjtx]

Double checked mileage from house to work today. Google maps says 12.4, my odometer says 12.2. At that rate (if even google is accurate) I only lost about 10 miles on the odometer for the last fill up. Which would've only provided a net gain of <1mpg.

[Delibes]

Originally Posted by andrewjtx

Double checked mileage from house to work today. Google maps says 12.4, my odometer says 12.2. At that rate (if even google is accurate) I only lost about 10 miles on the odometer for the last fill up. Which would've only provided a net gain of <1mpg.

If it only happens with the AC on, try taking a look at the compressor. If it happens all the time, it may be the injectors... try adding injector cleaner and get back to us with the new mpg tankfuls! Hopefully that should improve slightly, more and more over time.

Other than that, it's great to see fuelly getting populated by Mercedes enthusiasts. Keep it up!

[Delibes]

Originally Posted by andrewjtx

Double checked mileage from house to work today. Google maps says 12.4, my odometer says 12.2. At that rate (if even google is accurate) I only lost about 10 miles on the odometer for the last fill up. Which would've only provided a net gain of <1mpg.

Any updates?

[Yak]

Originally Posted by andrewjtx

Trust me, I have.

Glow plugs are great / nearly new with <15k on them
All filters are regularly checked/changed
Valve adj was done <15k ago
Compression is good
start up (even cold) is great
No smoke
Good power / throttle response
Engine sounds great
My 30-mile RT commute each day is on a mixed speed road ranging from 45mpg-65mph with a few lights interspersed.
Brakes aren't dragging

The only things at this point I have not exhausted are:
Injectors
IP timing
Replacing the cheap Michelins

I'm also coming off a bout with non-optimal oil and flushing in a few rounds of 15w40. The next OC at 171,500 I will be doing another valve adj, timing chain check and replacing a few leaking seals (turbo return, filter housing). If those items don't show some improvement, I'll be pulling the injectors for Monarch nozzles and pop/balance testing.

I just starting running the A/C again and that's where I'm getting the 18mpg.

What size tires? Wider tires will make a real difference due to resistance, and larger tires will make a perceived difference based on the math.


If larger, your odometer will read low, so will your speedometer; which sort of sounds like what you've got. Check the link for some example sizes and rotations/mile

http://www.buicks.net/shop/reference/tires.html

[snookwhaler]

Originally Posted by andrewjtx

You know. That's one thing I absolutely haven't checked. I also might borrow a GPS from a friend and verify.

Come to think about it, I was pulled over the other day (no ticket) for doing 70 when I swear I was doing 60.

Update: just ran out for lunch and the trip odometer rolls over smoothly.

I originally thought this of my car. I checked it again and again and based on the readings of the pump and ODO, I never got over 21 to 22 MPG. As it turns out my car had the speeo/odo swapped out at some point in time. It was 17% off!!

Needless to say... After using a GPS for a few weeks and then going some distance over "measured miles" on the interstate... I found the problem and corrected it.

I used to be really "anal retentive" about checking my mileage. But, that was when I was still driving my Passat TDI's. I sold those cars years ago... No more spread sheets, etc... I just check my vehicles mileage every few months to see "where I am at". If it is the same, I go on. If it changes, then I know something is wrong and I start troubleshooting. Usually the problem points itself out before it ever gets to that point.... There are much more important things in life to worry about.