'13 Passat TDI SE Reduced MPGs

Dcwhybrew

Well-known member
Joined
Nov 22, 2014
Location
Oklahoma
TDI
2013 Passat TDI SE
My 13 Passat TDI SE has recently dropped fuel mileage from 40-42 to 37ish. I am driving the same route every day. Two weeks ago I had the 100k mile service completed. I had new tires installed last weekend. Today I had the alignment checked. We have had consistent weather (sunny). This is odd. If it continues next week I will schedule an appointment to have the brakes checked (to make sure one of them isn't dragging). Other thoughts?
 

ZippyNH

Veteran Member
Joined
Apr 22, 2015
Location
Southern NH
TDI
2015 JETTA TDI SE
New tires...can you post the old type and the new type...some very high treadwear tires have high rolling rest...thus lower mpg till thet are worn...
You went from about 2/32 of rubber to 8/32 or so as a guess...
So you are more "squish" so less efficient rolling....
Then add into it the tires are Slightly larger till thet wear, you are using slightly more tq, and covering slightly longer distance with each rotation....just a few fractions of a % here and there....but they all add up!
 

Dcwhybrew

Well-known member
Joined
Nov 22, 2014
Location
Oklahoma
TDI
2013 Passat TDI SE
Did they install any software updates as part of the service?
I asked them about any software updates. The service advisor denied that they installed any. Interestingly, a lady I work with has a VW Jetta TDI. I believe when she hit 100k miles (like I just did) her car had reduced mpgs after being serviced. I still wonder if the dealer did install a software update or cleared out some performance parameters that had been stored in the ECU.
 

Dcwhybrew

Well-known member
Joined
Nov 22, 2014
Location
Oklahoma
TDI
2013 Passat TDI SE
New tires...can you post the old type and the new type...some very high treadwear tires have high rolling rest...thus lower mpg till thet are worn...
You went from about 2/32 of rubber to 8/32 or so as a guess...
So you are more "squish" so less efficient rolling....
Then add into it the tires are Slightly larger till thet wear, you are using slightly more tq, and covering slightly longer distance with each rotation....just a few fractions of a % here and there....but they all add up!
The old tires were the Continental Contiprocontacts with 4-5/32. The new tires are Michelin Primacy MXM4s with 9.5/32
 

HBarlow

Veteran Member
Joined
Nov 3, 2012
Location
Crosby County, TX
TDI
2009 Jetta Sportwagen, 2016 Audi Q5 TDI
My VW dealer has performed the required service every 10k miles since I bought my VW TD used four years ago including the 100k and 110k. I noticed no change following service.
 
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