New here, question about my 35 mpg fuel economy

Hi all, a good friend of mine referred me to this site. This may not be the right area for this question, but I'm a bit stumped. I drive about 70/30 hwy/city.



I bought a 2012 Golf TDI 2 door, 6 speed manual, a few weeks ago. This is my first diesel ever. 45000 miles currently on it. I absolutely love this car.



So far, every fill up I get right about 35 mpg (I fill up at half a tank), no matter how I drive. I calculate this by miles traveled and amount of gas to fill up. The in dash mpg states about the same 35mpg.


I started out driving it as I would my last car, 75mph+ on the parkway to work. About 35mpg on that tank.



Installed K&N air filter (I know this is bad now)



Second tank I never got over 70 unless I had to pass someone, About 35 mpg.



Had a new set of correctly sized tires installed, previous tires were slightly wider, not the correct size.



Went back to my regular driving habits, About 35mpg.


Anyone else had a similar experience? There is no check engine light on. I'm thinking the MAF is bad, either when I bought it or after I put on the K&N filter.


Any ideas or suggestions appreciated!

Depending on how you drive, 35 MPG could close, but still off what you should expect. I know people here see 38 or so in some driving conditions.

Do you know the age of the air or fuel filter? If not I'd replace those. And check tire pressures. VW suggests 38 all around. Some people run more, but you should see decent FE with 38 PSI.

< I calculate this by miles traveled and amount of gas to fill up.>

Maybe you should try diesel.

Indigo - thanks for the info! Air filter is new, but K&N so I'm wondering if the consistent mpgs is because of faulty MAF. Fuel filter is next on my list, but going wait until I have a VCDS. No idea on how well the maintenance was kept up, I have a feeling all the 40,000 maintenance items were skipped but don't know for sure. I did an oil change last week and it did look like it needed it.



Belome - thanks old habits die hard, this is my first diesel so with luck I'll learn to say that or fuel instead of gas

belome said:

< I calculate this by miles traveled and amount of gas to fill up.>

Maybe you should try diesel.

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merciless, should we do that by wight or by volume?
Might be stuff over here-
VW MKVI-A6 Golf family including Jetta SportWagen (~ 2010-2014)

But seriously, especially if family members or others are going to drive it, it's good to get in the habit of saying "diesel", never "gas".

One thing to check is to make sure your E-Brake is not dragging. Sometimes a problem on Dubs.

With the brakes cold, go on a drive for say 5 miles and use very little brakes. stop an check the temp at all 4 wheels and if you do not have a dragging brake, all 4 should be fairly cool and about the same temp.

Bob - Luckily its only me. Plus it has some sort of warning system on there should someone other than me drive it (or should I have a memory lapse) there is a warning thankfully!


Ol'rattler - thank you! I will check that.

If the K&N filter was new I doubt it affected the MAF. People here are dead set against K&Ns, but I think they cause MAF problems when not re-oiled properly. Still, I believe OE supplier filters are better.

If you don't want to wait for VCDS a lot of people (and shops) replace the fuel filter by filling the canister after inserting the new filter and putting the cover on, and cycling the key two or three times before starting the car.

And I agree on the dragging brakes. Pretty common on that platform, perhaps exacerbated by the time the car sat.

Thanks Indigo! I have been going back and forth about doing the fuel filter that way but if I can get the VCDS soon I'll wait. And I'll check the back brakes...already checked the front ones and they looked fine and thick. However the car does not stop on a dime so the rear ones may be dragging and therefore worn.

And I bit the bullet just now and ordered the VCDS from Ross-Tech. Should be interesting to use!

Good for you, well worth it for a car that new. And it's also the most economical believe it or not.

I feel like you should be getting better mileage, but if your 30% city is a lot of stop and go and sitting idling then that can be a real mileage killer. I haven't owned my "fixed" car for too long, but I don't think that your mileage is way off the mark. I think I've seen tanks of around 36-38 MPG in my wagon with the same engine.



I'll be curious to see what you find with you car.

Thanks Bob and Kite. My city driving isn't bad, but that could be part of the problem. At least I'm consistently getting better mileage than anything else I've owned, and I swear this car feels like it has just as much power than the 170hp eclipse I had previously. Must be all that torque

I get similar numbers to you out of my 09. I have logged over 60 tankfuls so it is pretty representative of what it gets real time. If I fuel up and hit the highway for a trip, it will read in the fifties for MPG so I can still have some bragging rights.



The car gets better mileage overall than any car I have owned in the past and I like the car. I doubt you will find anything wrong with VCDS but it is a necessary tool to have in my opinion. Ditch the K&N not just for potential MAF damage but mainly for dirt ingestion. They do not filter near as well as the stock filter.

Thanks pdq, that helps my feelings a bit. Since this is totally new to me, I'm paranoid about the car being in perfect shape, updated maintenance, good MAF, etc.

Mark1331 said:

...Air filter is new, but K&N so I'm wondering if the consistent mpgs is because of faulty MAF...

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Get rid of the K&N ASAP.

Mark1331 said:

...I did an oil change last week and it did look like it needed it...

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It's a diesel. Your brand new amber colored oil will look like that very soon after changing it. It is normal. Just change it and the filter every 10K -15K miles and you will be fine. Use only VW approved 507 spec. oil.

My car has been delivering 38 MPG over 5 fillups, so I think you're in range. I looked at the fuelly for our old JSW TDI and over 5k miles that I had bothered to enter it delivered 40 MPG on average. So a 2 MPG reduction because of the fix seems reasonable to me.



My MFD shows a long term mileage of 40 MPG so it appears to be optimistic by about 2 mpg.



My MK4 delivered 45-47 MPG no matter how I drove it. I do miss that car.

Thank you Sailor and Kite for your advice!

2000 Jetta TDI 5-speed, totally stock, no engine, injector, etc. mods. First 240,220 miles, every fill-up logged in a spiral notebook by previous owner, and myself. Overall 51.86 MPG, probably 70/30 hwy/city. Total mileage at last fill-up 240,220, total fuel used 4,632 gallons.


First fill-up was at 504 miles (dealer must have filled it at deliver) and it took 9.931 gal on 6/12/2000 at $1.439/gal
If my driving is exclusively "in city", it average 43 - 45 MPG, approaches 58 - 60 hwy driving.


Highest fuel price June 2008, 4.809/gal
Lowest fuel price December 2001, 1.179/gal