2015 Jetta post phase 1 of fix MPG

dodgeit

Member
Joined
Dec 4, 2016
Location
South Carolina
TDI
Jetta
Car is as peppy post fix, but suffers on the top end a bit. Nothing to worry about, but mileage is down 6 to 8 mpg ( hand calculated ) depending on where I fill up. Pre-fix 46 at the worst and 49.93 at the best. 39 and 40.5 now.

On a side note the Lie O meter is closer to being right. Mileage driven is combined interstate 60 mile per day and around town on the weekends.

Curious as to what others are really seeing. Dealer said -2 to -6 is the norm post fix of all cars they have done.
 

93celicaconv

Veteran Member
Joined
May 22, 2013
Location
Wisconsin
TDI
Turned in my 2010 Jetta TDI Cup Edition to VW, DSG, Nav, Sunroof / Replaced with a 2015 Passat TDI SEL Premium
Car is as peppy post fix, but suffers on the top end a bit. Nothing to worry about, but mileage is down 6 to 8 mpg ( hand calculated ) depending on where I fill up. Pre-fix 46 at the worst and 49.93 at the best. 39 and 40.5 now.
On a side note the Lie O meter is closer to being right. Mileage driven is combined interstate 60 mile per day and around town on the weekends.
Curious as to what others are really seeing. Dealer said -2 to -6 is the norm post fix of all cars they have done.
For a 2015 with the EA288 engine (new TDI), at least for the 2015 Passat, there was no MPG change pre- vs. post-fix. I am surprised your Jetta is exhibiting this kind of mileage setback. Although, you may be comparing winter cold fuel efficiency against your overall average from earlier. During the same month(s) of driving pre-fix, are those months much different than the same months post-fix?
 

dodgeit

Member
Joined
Dec 4, 2016
Location
South Carolina
TDI
Jetta
For a 2015 with the EA288 engine (new TDI), at least for the 2015 Passat, there was no MPG change pre- vs. post-fix. I am surprised your Jetta is exhibiting this kind of mileage setback. Although, you may be comparing winter cold fuel efficiency against your overall average from earlier. During the same month(s) of driving pre-fix, are those months much different than the same months post-fix?
My winter fuel mileage was always 46 - 47 before
 

93celicaconv

Veteran Member
Joined
May 22, 2013
Location
Wisconsin
TDI
Turned in my 2010 Jetta TDI Cup Edition to VW, DSG, Nav, Sunroof / Replaced with a 2015 Passat TDI SEL Premium
My winter fuel mileage was always 46 - 47 before
Probably safe to say Wisconsin winters and South Carolina winters are not the same. In Wisconsin, fuel economy normally drops by 20%-25% of that in summer. Your past history shows a far less winter fuel efficiency drop. I've only had my 2015 Passat TDI SEL Premium since mid-November, and it was already pretty cold here then. I don't know what the mid-summer fuel economy will be yet.

That said, VW clearly stated the fuel economy impact on Phase 1 2015 EA288 engines would be minimal, if any (0-2 MPG loss possible). If yours is that much different with no other possible factors other than the Phase 1 repair, I would suggest you take your car back to the dealer service shop to find out if something isn't quite right with it.
 

joshhol

Well-known member
Joined
Sep 5, 2017
Location
AP
TDI
2014 JSW TDI 6MT no sunroof, 1976 MBZ 300D & 1963 MBZ 220S; sold 2013 JSW TDI 6MT
I was having a similar issue with my Gen 1. I got the fix right as we headed into the coldest few weeks of the winter (Illinois). My mileage sucked. I was really disappointed with the fix and kicking myself for not taking the buyback. However, some encouragement from forum members said to wait for warm weather. On a recent mild day, I was able to get reasonably good mileage. My theory, and it's just a guess, is the emissions system didn't really "try" all that hard before during cold weather. Now I suspect it's working harder to reduce emissions during the cold and it's sapping our mpg's.
 

dodgeit

Member
Joined
Dec 4, 2016
Location
South Carolina
TDI
Jetta
Well the weather has warmed abit here and the Lie O meter is pointing towards a better figure. Will know when I fill up in a couple days. Have 460 miles on tank and it hasn't moved off the the half mark yet. Fingers crossed it is the computer relearning the fuel curve, causing the low mpgs. Flash sets fuel map to X then computer starts to adjust map based on engine needs and driver input. At least that is the way gas ECM works.
 

Smashed Ixnay

Veteran Member
Joined
May 7, 2010
Location
Auburndale, FL
TDI
2015 Passat TDI SEL
I'm happy with the mileage, but the first full tank the gauge was off by 2mpg. I don't know if having the car sit 1 hour was the cause of that. My wife had to use the car one day and got to work real early, so she was in the parking lot for 1 hour idling. It hurt to hear that since I was doing a great job at finally figuring out my mpg for a tank of diesel. I still was able to get about 45mpg on that tank.
 

dodgeit

Member
Joined
Dec 4, 2016
Location
South Carolina
TDI
Jetta
Filled up yesterday and can report an improvement to 43.97 mpg hand figured. So that's progress. I have noticed in my area that particular filling stations will have high BTU (high MPGs) fuel in their tanks for a month or so, then start filling their tanks with a lesser BTU fuel. This last tank full was at the same chain store but different location.

I will report back on this tank as well.
 

dodgeit

Member
Joined
Dec 4, 2016
Location
South Carolina
TDI
Jetta
New update: Car has settled into 41 to 43 mpg (calculated) per tank. The lie O Meter still shows wild swings day to day, but this stems from Cold temps in the morning to warmer temps in the afternoon. In the morning it shows 41 mpg and on the afternoons that are warm it gets into the low 50's. So it is clear the new tune (post fix) is not a fan of cold temps.

On a side note the Service mgr at the local VW location told me that intake manifolds are sooting up on post fix cars, causing poor MPG. They are being replaced/cleaned under warranty. Only way to know is when you get a CEL. I don't think this is my problem cause MPGs tanked soon as I got the fix.
 
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