Fuel economy - what am I doing wrong?

eagle

Veteran Member
Joined
Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Hi, all.

I'm not new to TDIs -- I owned a 2006 Jetta TDI DSG from 2006 to 2010, and managed 38 mpg over the 60k miles I tracked (out of the vehicle's 65k total miles). Best tank was 56 mpg (real), and on trips I easily got high-40s.

About 2 months ago I bought a 2013 Jetta TDI DSG, and my average economy has been 26.8 mpg, with a max of 30.6 (all highway), and with decreasing fuel economy with every tank. I have tried various things to improve my economy (varying my driving style) but nothing seems to work.

My 1.8T had a lifetime economy of 26.7 mpg over the time I tracked it (109,255 miles out of 160k total miles). Best tank was 35.0 (real), so I do know how to get economy out of a car.

Any ideas on how I can figure out what I'm doing wrong?

Is it hopeless to expect good (TDI-level) fuel economy out of a "fixed" 2013 Jetta TDI w/ DSG?

Thanks.
 

Mike14VW

Member
Joined
Jun 13, 2019
Location
Wilpo
TDI
2014
Not the only thing you can do but change the fuel filter. I have a 14' non DSG and gained 4 mpg's.

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35 Yr Dsl Veteran

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Ft. Pierce & Lake Placid, FL
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2012 Touareg TDI Sport
Not the only thing you can do but change the fuel filter. I have a 14' non DSG and gained 4 mpg's.

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I changed the fuel filter of my '98 Jetta TDI every 40K miles, instead of recommened 20K, but never noticed a bit of change in MPG with filter change. Should have NO effect on MPG. All that happens when your filter starts clogging is decreased fuel flow, and therefore power. Just as if you go to a lower throttle setting. You should actually get better MPG with less acceleration & speed.
 

Mike14VW

Member
Joined
Jun 13, 2019
Location
Wilpo
TDI
2014
Yeah idk, never had it happen b4with changing the filter, the car had sat for a year up to the fix. I had been tracking it since I purchased the car was averaging 43-44 almost every fill up. Changed the filter after half a dozen fill ups and has stayed at 47-48 every fill up.

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Mike14VW

Member
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Wilpo
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2014
Maybe just a fluke but I did nothing else differently.

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eagle

Veteran Member
Joined
Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Last week I had it at the local shop for an oil change, and had thought of also replacing the fuel filter. I probably should have done it. I did the oil change because I don't know what type of oil the used car lot put in it, and I figure that an oil change is cheap insurance to know that it's the right oil.

Anyway, you can see all of my vehicles Fuelly:
- 2013 TDI: http://www.fuelly.com/car/volkswagen/jetta/2013/unixdude/925014
- 2006 TDI: http://www.fuelly.com/car/volkswagen/jetta/2006/unixdude/137846
- 2003 1.8T: http://www.fuelly.com/car/volkswagen/jetta/2003/unixdude/124470

My car was a VW buyback and it sat for 18 months according to Carfax. Maybe I should just have the filter changed -- no telling whether VW did it, and if they didn't it's probably gunked up.
 

Mike14VW

Member
Joined
Jun 13, 2019
Location
Wilpo
TDI
2014
Screenshot of my fuel log is attached. In the first 6 fill ups the only fill up that dropped below 40 was fuel I got at sheets. Do what you want, I was amazed that I gained that much from changing the fuel filter. It is a 6 speed and I do drive it to get the max mpg I can. My driving style has not changed all that much since the filter was changed. I used to have an 84 rabbit and I changed the fuel filter every year or two (was like $8 for the canister and easy to do). I tracked the mileage and never gained any mpg. This car I took to the VW dealer and had it changed because of all the electronics, still looks easy just did not want to mess anything up, if its possible.


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35 Yr Dsl Veteran

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2012 Touareg TDI Sport
Screenshot of my fuel log is attached. In the first 6 fill ups the only fill up that dropped below 40 was fuel I got at sheets. Do what you want, I was amazed that I gained that much from changing the fuel filter. It is a 6 speed and I do drive it to get the max mpg I can. My driving style has not changed all that much since the filter was changed. I used to have an 84 rabbit and I changed the fuel filter every year or two (was like $8 for the canister and easy to do). I tracked the mileage and never gained any mpg. This car I took to the VW dealer and had it changed because of all the electronics, still looks easy just did not want to mess anything up, if its possible.


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You get much better MPG in HOT weather vs. COLD weather. This could be the answer.
 

Mike14VW

Member
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Location
Wilpo
TDI
2014
You get much better MPG in HOT weather vs. COLD weather. This could be the answer.
I understand that but middle of may almost into June is when I gained 4 mpg, like switch of a lite bulb....at this time of year, where I'm from.... we should already be out of the winter grade fuel and into warmer temps.... maybe an increase has nothing to do with fuel filter but that would have been the only thing that changed.

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eagle

Veteran Member
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Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Yeah, I think I'll get the fuel filter changed. Can't hurt -- other than my wallet.

Current tank is showing 22.7 mpg on the computer which has proven to always be 10% high. I can't be that hard on it.

I'm the third owner of the car, and the second since VW had. The owner before me had it for two months, and I wonder if it was for fuel economy or hill hold or delayed throttle response... maybe a combination of all of those.

Thanks.
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
Something is wrong with your car. When is your timing belt due? Time wise it should be changed soon anyway. I would consider finding a trusted mechanic from our list (a known good one) and having the TB changed properly, with all the required parts and set as well as a full service of everything. 20 mpg is just totally unreasonable for a properly running car. I would have requested a full service when I was buying it, personally, and have advocated for this here many times. These cars have sat for long periods sometimes and could really benefit from a good once over redo. Are your regens happening as needed? What is the soot and/or ash load of the dpf filter?
 

eagle

Veteran Member
Joined
Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Something is wrong with your car. When is your timing belt due? Time wise it should be changed soon anyway. I would consider finding a trusted mechanic from our list (a known good one) and having the TB changed properly, with all the required parts and set as well as a full service of everything. 20 mpg is just totally unreasonable for a properly running car. I would have requested a full service when I was buying it, personally, and have advocated for this here many times. These cars have sat for long periods sometimes and could really benefit from a good once over redo. Are your regens happening as needed? What is the soot and/or ash load of the dpf filter?
Sorry, I don't know what regens are, and I don't know what a dpf filter is.

They changed the oil but as far as I know that's all they did. I do have a good mechanic - a company run by some local enthusiasts, and they are very fair to customers. Great place.

I'll remember your "full service" tip for the next time I buy a vehicle.

Not sure about the timing belt - I'll check that.
 

Lightflyer1

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Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
You really owe it to yourself to read up here a lot and get familiar with these terms and others. These aren't really cars that tolerate not being taken care of properly or unaware owners (the newer emissions models especially). Nothing against you but there are some things you should be aware of such as the dpf filter (filters soot out of the exhaust stream and requires a burn off every so often, happens automatically and requires replacement when it gets filled with ash. One of the extended warranty items covered.) Regens are when the burn off of the dpf filter happens. About 10 minutes at very hot temperatures every 200 to 300 or so miles depending on what kind of driving you do. City driving will have shorter intervals than highway driving will. I can't explain it all here in one post but there is a ton of info here already for you to read and learn. It also helps to know things to explain to your mechanic better what the issue is. Don't wait too long on that timing belt either. If it breaks for any reason the cost to repair the engine will be great. Good luck and hope you can find the issue. If your mechanic can't find an issue you may want to try one of our trusted mechanics who specialize in these tdi's.
 

eagle

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Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Yeah, it's pretty clear that the 2013 TDI is not the same thing as a 2006 TDI. I'll do some research and reading up. Thanks.
 

Lightflyer1

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Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
The 2006 wasn't the same as the 2000 to 2003 either. As they get more complicated there is more to learn. My first was a 2006 Jetta. I have owned about 7 since then of differing years and models.
 

eagle

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Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Yeah, I know that the 90hp model was different from our 100hp 2006 model. What I mean is that the differences between that 100hp 2006 model and the 140hp 2013 model make the new one practically unrecognizable from the old one. It's not simply a newer version of the same thing - it's a completely different thing.
 

Lightflyer1

Top Post Dawg
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2015 Beetle tdi dsg
Not so much in my opinion. Pistons still go up and down and turbo still blows air. Only the exhaust components have some new stuff that is really different.
 

ffemtp

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SE WI
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2001 Jetta GLS TDI Deceased 11/2012, 2004 Jetta GL TDI Sold, 2012 Jetta TDI (Retruned to VW), 2004 Jetta TDI GLS 5spd
This might be a statement of the obvious, so forgive me....

How about checking / changing the AIR filter? I would not assume the stealer changed that when they did the "fix" or prepped the car for sale. If the car sat for a year + you might just have yourself a critter nest in there. Less than 5 minutes and a screwdriver and you'll have that verified. :D
 

35 Yr Dsl Veteran

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Ft. Pierce & Lake Placid, FL
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2012 Touareg TDI Sport
This might be a statement of the obvious, so forgive me....
How about checking / changing the AIR filter? I would not assume the stealer changed that when they did the "fix" or prepped the car for sale. If the car sat for a year + you might just have yourself a critter nest in there. Less than 5 minutes and a screwdriver and you'll have that verified. :D
A clogging air filter does NOT decrease MPG in a computer controlled, fuel injection engine. Only in the old days with carburetors would it have made any difference. The only effect will be less air flow and fuel flow to compensate, resulting in lower HP, top speed, and acceleration. Under those conditions, you will actually get GREATER MPG! :D
 

ffemtp

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Location
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TDI
2001 Jetta GLS TDI Deceased 11/2012, 2004 Jetta GL TDI Sold, 2012 Jetta TDI (Retruned to VW), 2004 Jetta TDI GLS 5spd
A clogging air filter does NOT decrease MPG in a computer controlled, fuel injection engine. Only in the old days with carburetors would it have made any difference. The only effect will be less air flow and fuel flow to compensate, resulting in lower HP, top speed, and acceleration. Under those conditions, you will actually get GREATER MPG! :D
I said nothing about mileage. I made a suggestion to check / replace the air filter. Period. Nothing more. I'll take a clean air filter over a dirty / clogged one any day of the week and twice on the weekend. :D:D
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
If something was wrong, such as retarded injection timing, it would be putting out lots of soot. He did not specify thusly.
This is a modern diesel engine with a dpf filter. It would be next to impossible for it to put out lots of soot unless the dpf filter was cracked or broken in some way. If it was putting out huge amounts of soot it would be almost unnoticeable except for the fact it would be doing a dpf regeneration really, really often, which would use more fuel resulting in decreased fuel economy, such as the OP has. This could easily be checked with an app or VCDS to rule it out. Checking for regen frequency and soot and ash load as well.

For the OP to have such low fuel economy they either drive in such a way to ruin economy or something is wrong with the car.
 

Fixmy59bug

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Joined
Aug 1, 2009
Location
Henderson, NV
TDI
2015 Passat TDI SE
What size tires does your 2012 have and what pressure are they at?

If I remember correctly, the biggest the 2006 would have had would be a 205/55-16 where as the 2012 could have up to a 225/40-18. Increased width means increased drag.

Also, with tire pressures, most dealers inflate them to what the door label says for comfort. Which, I believe, is 35 psi.

If you pump that up to 40 it still rides fine, wears fine, and you get increased fuel mileage.
 

eagle

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Location
North Carolina
TDI
2013 Jetta
To the earlier comment about the air filter, I checked it today, and while it is not brand new, it is clean and not clogged.

What size tires does your 2012 have and what pressure are they at?
They are 225/45-17. This is the "Premier" model, or whatever it was called, and it has the same size tires as my 2003 1.8T sport model had. I check them monthly and put them to the pressure listed in the door jamb, which I seem to recall is 33 psi, maybe it is 35.

If you pump that up to 40 it still rides fine, wears fine, and you get increased fuel mileage.
I used to do that trick in my 1.8T: it said 30 up front and 28 in rear, and I ran them at 32 front and 30 rear. I should boost the pressure in these and see what happens.

I have a fuel filter swap scheduled for Thursday, and I will fill up immediately after that. Based on what the computer says (it is always 10% optimistic), I expect this tank to be around 25 mpg.

Thanks.
 

scooperhsd

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Kansas City KS
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For comparision purposes, the only valid test for fuel consumption is to do it the old fashioned way - miles divided by gallons consumed.
 

eagle

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Location
North Carolina
TDI
2013 Jetta
For comparision purposes, the only valid test for fuel consumption is to do it the old fashioned way - miles divided by gallons consumed.
Absolutely, and that's what I do. In fact, I track with Fuelly.
However, I also track what the computer shows, and I have found it to be 10% optimistic. The computer currently shows 26.7 mpg for the tank, so I expect about about 24 mpg on this tank.
For comparison, here are my other cars: 2006 TDI and 2003 1.8T
 

eagle

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2013 Jetta
Yeah, I read that a while back. :) Most of it I understand, and what of it I understand does not explain my car's FE.

It does bring up a question. I see references to different kinds of TDIs, "PD" for example. I know that PD stands for Pumpe Düse, but I don't know which engine code corresponds to my car. Unfortunately the relevant wiki page isn't much help to the neophyte. How do I figure out which one my car has?
 

oilhammer

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outside St Louis (where it's safe)
TDI
There are just too many to list....
You have a "CR" family of engine, this simply denotes the type of fuel injection system, CommonRail.

VE came first, then PD, then CR, and now.... nothing [for us] :(
 

eagle

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Location
North Carolina
TDI
2013 Jetta
You have a "CR" family of engine, this simply denotes the type of fuel injection system, CommonRail.

VE came first, then PD, then CR, and now.... nothing [for us] :(
Thanks. I'm starting to understand that page a little more now. Looks like mine is one of the "2.0 R4 16v TDI CR" varieties, specifically probably one with one of the following ID codes, whatever that means: CFHC, CBEA, CBAB, CFFB, CBDB, CJAA.
 
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