Low Fuel Milage

Hello,
I purchased a 2012 Golf 2 Door TDI about a years ago and I have not been getting the best fuel mileage. I have been getting 33-35 mpg on the interstate (80 mph) over the last 10k miles. The car is stock other than GTI front and rear bumper with an neuspeed cutback exhaust. If I do 65-70 mph I can get up to 38 mpg. I have replaced the fuel filter a couple times thinking that could be the problem, but no change after filter changes. The car has great power, no smoking, or rough running. What ideas can you all share for why I am getting under 40 mpg? I have considered doing some emission deletes, but I live in a county with emissions testing. Any and all ideas / suggestions will be greatly appreciated.
Thank you
Kevin

Improperly designed exhaust systems can cut into fuel economy pretty significantly. What was cut out of your system? Any parts missing that had sensors plugged in?
On long cross-country runs covering three or four time zones, my '12 (6M, 2-door) averages a hair over 40 mpg running at the posted limits. I generally add Power Service White.

Tires are another consideration, if you have super sticky rubber, or underinflated tires.

Nothing has been changed with the exhaust or emissions system other than the nuespeed cat back exhaust. Tire pressure was checked prior to starting my last 2,500 mile trip with new pirelli all seasons. I got 33 mpg average (hand calc’d) on the trip with cruise control at 80 mph.
Thanks
Kevin


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I think your answer is in your post. You're going 80 mph.

ksing44 said:

I think your answer is in your post. You're going 80 mph.

Click to expand...

Is your guys fuel mileage that now doing 80?


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Your mpg sounds about right for a fixed CR TDI. I’m getting those number on the regular. If I do all highway on a tank and go 65mph I can get 38-39mpg on that tank.
Once my warranty is up I’m fixing the fix. Enjoy your warranty until that point.

Fuel economy drops off pretty drastically above 75 or so. Passats and Jettas have more slippery shapes. Traffic in Idaho, Wyoming, and Montana tends to flow at about 75 even when posted limits are higher. I've heard Texans run pretty fast.

I just bought a 2012 golf, 4 door 6 speed manual and drove it back from Vegas to SLC. I had the cruise on 80 most of the way, 85 for a large portion of it, and almost never went below 75. The display showed 40.8 mpg, when I filled it I calculated 39.8 mpg. The car has 90,000 miles so it should be fully broken in. All the emissions fixes were completed on 9/20/18

That's low mileage. My '12 Golf (sold) averaged about 43, and I saw 47.7 on a run from Michigan to MA, running at 80+ for a lot of the trip, A/C on the entire time. I only had one or two tanks below 40 MPG. Mine was a manual, don't know what yours is. And it was pre-fix, but it doesn't seem the fix has had a big impact on FE for most. I wonder if something else is affecting your FE.

That mileage seems a bit low, but within reason especially if you have a DSG which does a couple MPG worse on the highway I believe. I'm seeing about 37-38 mpg for my mixed commute - hand calculated.

I notice that you live in CO. If you're in the mountains and driving up and down grade a lot that will definitely hurt your mileage compared to people who live in the flatlands.

Anecdotal evidence seems to be that the fix cost about 2 mpg. That feels about right (or wrong!) to me.

Just couple thoughts...
Different bumpers that look more agressive front and back..... So I bet ya there is more drag....
Similarly wider or high performance non low rolling resistance tires can cost you..1-3 mpg...more if "summer" tires...and a "hi" performance exaust...by definition that's more hp, and that's lower mpg....ok you get mostly sound on a turbo car...but still...
High-speed...40 mpg at 80 isn't bad stock...so modded 35+ isn't unexpected...bet you would do 40 at 70...
Enjoy your car...you bought a faster looking/faster sounding car than stock...I would have expected lower than average mpg.

I love these questions... 80 MPH?

1. Warm car up.
2. Get on freeway and set cruise to speed limit 55, 60 mph (no faster than 65)
3. Zero out the fuel totalizator to zero.
4. AC should be off and no cargo or passengers.
5. Drive about 10 miles on flat and level highway, light winds.

You should see 50 mpg.

Get off freeway, get back on freeway going back from where you started, get back to speed, cruise control set,
reset MPG counter and repeat. If you did not see 50 MPG on first leg set 5 mph slower speed. DO NOT SPEED.

If you can not get 50 mpg at 55 mph you have something wrong. Make sure your tires have 40 psi min.

The question is legitimate. And the OP definitely has a problem.

Maybe things are different in TN, but on the freeway I use for my commute the left lane runs at 80-90 when traffic allows. Speed limit is 60. Anyone driving the speed limit creates a significant backup (and is, in my opinion, a hazard) and is treated aggressively by other drivers (tailgating, passing and cutting in close to the car, etc.). Sometimes driving the speed limit isn't wise.

There is usually a state trooper presence on this road, too. They tend to ignore anyone driving less than 80, and even those driving over 80 if there's a group of people going that speed. Best part is you're allowed to drive in the breakdown lane during peak periods. And the breakdown lane is often the fastest moving lane. Merging is fun.

My ALH gets between 46-50 MPG in driving that includes my commute. So something's amiss with the OP's car.

If you can make the drive to Golden then see anuthee at https://www.dieselland.net/

Great results improving fuel economy in those cars, no "deletes" needed.

Ive had 2 sportwagons, used them original stock, "fix #1" stock, fix #2 stock, tuned, tuned and deleted, with egr, and without, and mine have always gotten over 40 mpg. posible its your catback, might be causing your turbo to over boost.. guy who tuned my first car told me going with a 3 inch downpipe caused issues, not enough back pressure allowed the turbo to overboost and the engine to cut fueling, easy to see where having your engine management system fighting itself could really mess with your mileage, especially when you are talking only 10-15%, no idea if this aplies to whats up with yours, but its a possibility

My last 10 fill-ups in my 2010 Golf TDI with the fix. I have about 165K miles right now. I spend time on the PA Turnpike, 35 miles each way on my commute, between 70-80 miles per hour. I also work from home some days and do errands close to home on weekends.

Last 10 tanks:


on Flickr

my 2010 Golf TDI. Some of the variability over time is because my commute changed to a shorter drive for a while about 2 years ago, now I'm back to the longer commute but I also work from home some days. I also drive a bit faster now during the commute, because they raised the speed limit and everyone is going faster.

7 years of averages, 2010 - 2017


on Flickr

ksing44, thanks for sharing. My mileage is mirroring yours for 2017. I attribute most of it to my relatively short commute that is also includes a very long downhill/uphill run of a couple miles. I'm at 37.1 MPG on 9 fill-ups. I would love to be averaging 40, but I think it will take a tune to get me there.

^^I guess a tune could get me back to a 40 mpg average or maybe staying in the slow lane on the highway and not using my car for too many shorter trips. Those earlier years were dominated by mostly highway driving at about 60-65 mph. The speed limit was increased on the highway I travel and I spend my time in the fastest lanes. I also have more frequent short trips. And the much more frequent and longer short duration regens most certainly have an effect on mpg.

On a single trip that's all highway, mid 70s mph not sustained at 80 mph for long duration, I still get into the 40s for average mpg. But even then I'm sure it's a few mpg less than it was before the fix. Then as soon as I mix in some shorter trips the average mpg for a tank of fuel typically drops into the mid 30s. And there is nothing "wrong" with my car.

When the extended warranty is done, I might try the delete thing to breath a bit of new life into the car and to have some fun before it's over and I move onto a GTI. By then my Golf TDI will 10+ years old and probably have ~200K .

Slow down. 80mph is killing your fuel economy. Air resistance (drag) is exponential, not linear. My commute is highways, between 55-60mph, and I can get 50+mpg with my 2012 TDI 6MT.