Fuel economy - what am I doing wrong?

Joined
Sep 20, 2019
Location
Salem or
TDI
Mk4 golf tdi bew vnt17
Poor fuel economy

My tdi is experiencing low fuel economy, 32 mpg in the past ive gotten 40mpg with a 2 bar map and vnt17 turbo.
Ive gotten a check engine light with intermittent excess fuel in the exhost and when i looked at my egr it was gunked up so i cleaned it. I was wondering if my problem a dirty intake or bad fuel injectors. Listed below will be my readings.
Mas air flow 300 mg/str
Boost pressure 1020 actual and specified
Ingection
Cyl 1 -.75
Cyl 2 -1.25
Cyl 3 2.87
Cyl 4 -.85
Fuel consumption 1.8 l/h
All above is at idle
O2 sensor 3.69 at idle and 16 when cruising at 45 mpg
 

eagle

Veteran Member
Joined
Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
I thought I'd update the group, and thank everyone who commented.

This weekend, I finally took a day trip to a nearby city, and my car indicated 45 mpg (real mpg ~40, but I didn't fill up and calculate it). My car has never indicated 45 mpg to me before, even on a similar trip I took right after I got it. That tells me that replacing the fuel filter fixed the fuel economy issue my car was having, and it also confirms that my short 5.5-mile-with-10-stoplights commute is the main reason my car produces only 25-30 mpg during my daily drive.

I guess a TDI wasn't the best purchase for my driving needs, but it should hopefully last me a very long time.

I note a drop in fuel economy of my other vehicle, a 2008 Honda Odyssey, about a year ago. I moved about a year ago, and now everything for me is a 7-minute, few-mile drive away, versus a 20-minute, 10+-mile drive like it was before.

As another poster commented: with a commute of only 5.5 miles, why do I care about fuel economy? Good question. For now, I'm off to enjoy my car and not care about its economy. I'll also make an effort to take a monthly day trip to a nearby city in order to give it some highway miles.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
Think of it this way, your TDI may only net you 25-30 MPG during your intense city driving, but a gasoline fueled version of the same car will only get about 15-20 under the same circumstances.

So it's all relative.

This is where hybrids really shine, because they offset the load of the engine under these inefficient stop and go situations with an electric motor driven by a battery that can recoup energy by regenerative braking. Of course, if there isn't any hybrid you'd care to drive then...
 
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eagle

Veteran Member
Joined
Apr 14, 2004
Location
North Carolina
TDI
2013 Jetta
Think of it this way, your TDI may only net you 25-30 MPG during your intense city driving, but a gasoline fueled version of the same car will only get about 15-20 under the same circumstances.

So it's all relative.

This is where hybrids really shine, because they offset the load of the engine under these inefficient stop and go situations with an electric motor driven by a battery that can recoup energy by regenerative braking. Of course, if there isn't any hybrid you'd care to drive then...
I get what you are saying, but my previous car was a 2003 1.8T Jetta. In the same driving conditions it generated 27 mpg, more than the TDI. that’s what started the whole thing.

And yes, no hybrid for me.
 
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oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
That is amazing, I would never have thought that. I do not do much city driving, but none of my spark ignited Volkswagens ever come close to my diesels. In most cases, they consume nearly double.

The only 1.8t I have ever had, and still have, is my 2004 Passat wagon, but it is an automatic and 4mo, so not a very good comparison. It struggles to get past about 23 on the highyway, LOL. No idea what it would get around town, but I never drive like that so it makes no difference.

The short lived Jetta hybrid is actually not an awful car to drive, really. And you can find them used for dirt cheap. The Ford C-max is another one, but again no longer available new. I do not really mind the Fusion hybrid either (again, going out of production) or the Camry. There is also a Corolla hybrid now. But in the case of some of these, the cost difference is substantial, so unless you drive a LOT in the city, you really won't save much money over just buying the more basic version of the same car. Although the hybrid Corolla is only about $4k more than the base version, which isn't too terrible.
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
My local Guru had a very short commute for a while and tends to idle his car a fair amount. His '12 Passat was getting high 20s summer, mid 20s winter. But if it were a 2.5 he'd probably be seeing FE in the teens. So as oilhammer says, it's all relative.

The older cars don't take a big a hit in short trip driving, probably because they're not working to keep emissions equipment warm.
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
I'll also make an effort to take a monthly day trip to a nearby city in order to give it some highway miles.
With that kind of short trip driving you better pay close attention to regens and not just some highway miles. You will be in big trouble with the emissions system. The dpf needs to clean itself and it is pretty often in that kind of driving regimen.
 

nucklehead

Veteran Member
Joined
Jan 30, 2014
Location
Ephrata Washington
TDI
2013 Golf TDI W/DSG
I thought I'd update the group, and thank everyone who commented.

This weekend, I finally took a day trip to a nearby city, and my car indicated 45 mpg (real mpg ~40, but I didn't fill up and calculate it). My car has never indicated 45 mpg to me before, even on a similar trip I took right after I got it. That tells me that replacing the fuel filter fixed the fuel economy issue my car was having, and it also confirms that my short 5.5-mile-with-10-stoplights commute is the main reason my car produces only 25-30 mpg during my daily drive.

I guess a TDI wasn't the best purchase for my driving needs, but it should hopefully last me a very long time.

I note a drop in fuel economy of my other vehicle, a 2008 Honda Odyssey, about a year ago. I moved about a year ago, and now everything for me is a 7-minute, few-mile drive away, versus a 20-minute, 10+-mile drive like it was before.

As another poster commented: with a commute of only 5.5 miles, why do I care about fuel economy? Good question. For now, I'm off to enjoy my car and not care about its economy. I'll also make an effort to take a monthly day trip to a nearby city in order to give it some highway miles.

My first TDI was a new 2013 Jetta Premium. Over 3.5 years of driving 22k miles I averaged 40.1 mpg combined driving. I really loved that car, but I sold it back to VW because they offered me almost $1k more than I paid for it OTD! Hard to say no to that. When I heard the 'fixed' TDI's were back on the market I went shopping, and picked up my 2013 Golf TDI. I expected similar MPG as I got with the Jetta. I was disappointed, MPG was right around 35-36, with one 'exceptional' tank of 38. Golfs should get better FE than the heavier Jetta. It wasn't happening. I track all my FE via Fuelly so those numbers are accurate.

I decided to search for a decent economy tuner, and read a lot about Kerma and Malone. Kerma had the flash unit that lets you install the 'fixed' tune should you need to take a trip to the dealer. Everything appears stock unless you can read the OBD port. All the smog gear is there, and mostly works like it should.

Since I have a great warranty I decided this was the way to go. My first full tank on the tune netted me 43.1mpg. That's more like it! My last tank was a 10% bio-diesel fillup, FE dropped to 42.3mpg. Regens are about like normal, every 300 miles or so. I don't drive the Golf in summer much for short trips, the Miata is more suited to that 10 mile trip to the golf course 4 days per week. With fall being cold I'm back in the Golf for that 10 mile (one way) trip for golf, and I'll need to listen for regens, but I expect the FE to be somewhere around 38 or so during the cold months. My overall driving is 60 highway 40 city. If I interrupt a regen on the way to/from, I can take the long way there/home. Highway speed (60mph) for about 15 miles. It worked for the Jetta, should also work for the Golf since the running gear is identical.

The Kerma tune has really brought the fun back in driving the Golf. I can probably burn off the front tires very quickly if I chose to. It'll bark the tires up until it shifts into 3rd gear. No need for Sport mode since it feels faster in Drive than Sport. Kind of odd until you remember that all the torque happens in the high teen RPM's, and not at 3500RPMs.

So I'm getting better FE and the engine puts out way more power than the stock 'fixed' OEM tune. As long as I can get at or over 40mpg per tank I'm happy. Whenever someone mentions that it'll take years of driving to get the price of that tune back I just hit the accelerator! I get it back little by little every time I feel the wonderful torque of that 2L diesel motor. Can't imaging owning anything else now. It's almost as much fun as the Miata, except nothing is quite like a vert.
 
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Jetta_Pilot

Top Post Dawg
Joined
Apr 14, 2005
Location
West Hill, Ont. Mexico mid October 2019 to end of
TDI
2015 Passat Highline TDI Candy White (SEL Premium) gone 2002 Jetta TDI
Regenerations most definitely continue at idle on my 2012 TDI Sportwagen. It's easy to observe if you monitor the exhaust gas temperatures.

That's what I do with my Scangauge. I have sat in my driveway and let it idle for a few minutes until the EGT was down to in the 300 deg range.
 

Jetta_Pilot

Top Post Dawg
Joined
Apr 14, 2005
Location
West Hill, Ont. Mexico mid October 2019 to end of
TDI
2015 Passat Highline TDI Candy White (SEL Premium) gone 2002 Jetta TDI
That tells me that replacing the fuel filter fixed the fuel economy issue my car was having, and it also confirms that my short 5.5-mile-with-10-stoplights commute is the main reason my car produces only 25-30 mpg during my daily drive.

I do not profess to be an expert, but I highly doubt changing the fuel filter would make the difference.


It only would if you are experiencing problems trying to accelerate, your engine sputters trying to get up to speed which may indicate a completely plugged filter.
 
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