Horrible MPG, but car runs excellently? 2012 Jetta Sportwagen

[coolusername]

If they are anything like dealers in the UK. Then without a CEL your unlikely to get anywhere.

You can imagine it. Hundreds of customers walking through the door. Blaming their MPG on exhaust

I'm optimistic, my dealer's been good to me. They spent two weeks last summer hunting down an occasional no-start that ended up being a slightly loose plug connection near the fuel pump, and then they replaced the crank position sensor and somehow got it all covered under the Dieselgate warranty. And I had a nice, covered rental during the time period.

 

[turbodieseldyke]

What happens if you disable the ODB port?

Probably sets off the reddest flags, sending you to a nitpicking, ball-busting referee.

 

[powermandan]

Probably sets off the reddest flags, sending you to a nitpicking, ball-busting referee.

In UK, they just abort test and move onto next one

 

[coolusername]

did you find soot in the tailpipe ?

Is this sooty? I can barely get anything on my tissue paper unless I scrub it round inside the exhaust pipe, but it still doesn't look quite right. I can't tell if it's just dirty from normal use or anything different.

 

[Shoveltrev]

so grey ash is good anything black is not. its really just another symptom. vw service bulletin sayspull the egr filter off of the dpf and check it for sooot. if there is any soot in the egr filter the dpf is compromised . . thats how they are supposed to do it anyway. my stock cjaa regens every 450 or so miles and thats half as much as yours and i do a lot of in town driving. a lot . like 300 out of those 450 miles .just my observations

 

[Shoveltrev]

something else you can check is do a cold soak test of all your temp sensers. egts coolant and iat. after it sits overnight they all should be within 10% of each other .

 

[Full Circle]

The EPA CARB CA clowns are choking the S+!t out of your engine.

 

[briandin]

I have a 2011 JSW CJAA which was entering regen mode often, and then through a code. The dealer determined it was a faulty thermostat and replaced under the CPO warranty the car was under at the time. The fuel economy improved substantially after that. Not saying that is the issue. My car has 114K miles and now I am bringing it back one last time (the magic 54,000 miles from the post sale dieselgate emissions remedy tolls in exactly 1,825 miles) due to a fuel leak (pretty sure its an injector seal). Both of these issues have affected fuel economy but each only to the tune of about 3-5 mpg.

 

[ZippyNH]

Interesting you said "new tires"...
They stock size? Rims?
Usually new tires is a couple mpg hit...more rubber, more squirm, and slightly bigger diameter....plus the cheapest or ones that give you super long life can be worse. Not saying it's all you problem, mpg issues can be a death by a thousand cuts....
One dragging brake.... roof rack... slightly wider tires.... Heavy aftermarket rims that can sometimes make extra drag (yes big open style rims for cooling)....sometimes plastic air dam parts missing or broken, driving style, fuel....look at the details...lots of little issues equal a big issue
Good luck....