Experiencing Decreased MPG 2010 GLK W/ 85K Miles
Thread Starter
Junior Member
Joined: Jul 2013
Posts: 34
Likes: 2
From: Cincinnati, Ohio
GLK 350 2010
Experiencing Decreased MPG 2010 GLK W/ 85K Miles
Hello fellow GLK Drivers -
My 2010, 85k mile GLK is experiencing decreased MPG. Was seeing a stable 20 MPG overall, my mixed city/hwy driving is averaging now a little under 17 MPG.
I have never had spark plugs changed - could this be culprit? Air filter?
Asking for potential causes and paths to troubleshoot! Thanks in advance for the advice and expertise
My 2010, 85k mile GLK is experiencing decreased MPG. Was seeing a stable 20 MPG overall, my mixed city/hwy driving is averaging now a little under 17 MPG.
I have never had spark plugs changed - could this be culprit? Air filter?
Asking for potential causes and paths to troubleshoot! Thanks in advance for the advice and expertise
Senior Member
Joined: Jul 2014
Posts: 422
Likes: 61
From: South East US.
2015 GLK350
I assume you have a GLK 350. When is the last time you had a tune up? Spark Plugs, air filter, winter mix gas, wheel alignment, change in driving habits/route can all be contributing factors. It could be any of many things.
Super Member
Joined: Aug 2011
Posts: 861
Likes: 38
From: Philly area
350 GLK, C280
Winter fuel is oxygenated and gives lower mpg. Depends on state and location. Increase methanol gives lower mpg. Don't know where you live but biggest problem right now is the low temperatures. Vehicle needs to run richer when cold and adds fuel when air is dense. If yo do short driving, less than 15 minutes mpg will be very poor in winter.
MBWorld Fanatic!
Joined: Jan 2009
Posts: 2,780
Likes: 115
From: Northern NJ
GLK 350 / Porsche 993
I only get 20-22 on highways. Lucky to get over 15mpg in winter with town driving. I'm a bit heavy on the gas and tranny is always in "S".
btw do you measure or rely on the computer? I noticed that computer can be off by 2-3mpg sometimes.
btw do you measure or rely on the computer? I noticed that computer can be off by 2-3mpg sometimes.
Thread Starter
Junior Member
Joined: Jul 2013
Posts: 34
Likes: 2
From: Cincinnati, Ohio
GLK 350 2010
Thanks all! I live in Southern Ohio and it's been the coldest winter in decades. Typically I was getting 340 miles to a tank of premium gas - now getting 280 ish. The explanations make sense - it was the advent of the really cold weather that I noticed the mileage drop
Super Member
Joined: Aug 2011
Posts: 861
Likes: 38
From: Philly area
350 GLK, C280
NYCGLK, if the NYC stands for the Big Apple, I am surprised you get any millage! Last week, I was stuck in the Lincoln tunnel traffic for an hour because they closed a tube. Glad I don't do that every day! Talk about low mileage.
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MBWorld Fanatic!
Joined: Jan 2009
Posts: 2,780
Likes: 115
From: Northern NJ
GLK 350 / Porsche 993
I don't drive in NYC much, I take bus to work. But yea I've had low teens while stuck in LT once.
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