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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old April 9th, 2018, 07:52   #1
Join Date: Mar 2013
Location: Vancouver, BC, Canada
Fuel Economy: 40-42
Default Consistently low MPG

This may be long winded. My car (2002 Golf, 5 speed) has never got great mileage. I bought if from a VW mechanic in Newfoundland June 2012 with 90,000km. He bought it from an old lady, I gathered there was some catastrophic failure of the engine which made her not want to fix it, just buy a new one. The VW mechanic bought it, fixed it, drove it, then sold it. I'm assuming the timing belt failed.

Anyways, driving it in Newfoundland on mostly short commutes resulted in low mileage (36-38mpg). Now the car is with me in the Vancouver, BC area. The mileage hasn't improved too much, still high 30's. Over the past year I started fixing the car. Things like suspension rebuild, new rear brakes (and e-brake), cleaned intake, EGR removed, CTS, thermostat, etc. Mileage remained much the same, keep in mind my commute in Vancouver was short as well.

Next step was .216 nozzles and stage 3 Malone tune. This made the car fun to drive and didn't really effect MPG at all.

Finally, I'm now living outside of Vancouver. So my commute will be roughy 130km round trip. It is a mountain highway (hills, turns, downshifting, etc.) I was hoping to see a decent jump in MPG but my first tank since my longer commute gave me 39.5 MPG. Yesterday (after filling up and calculating MPG) I made my first attempt at playing with the VCDS. I was getting a decent amount of black smoke when accelerating hard. My timing was just above the max specification, I dialled it back to 56ish. Its in the middle of the upper portion of the graph. My IQ was also lower than I would like, in the neighbourhood of 3.2 I think. I moved it to 4.2. Hopefully this produces some improvements.

One final thing. I have a roof rack, which is a necessity to me for biking. What kind a mileage hit do you think that would cause? I would like to get mid to low 40's, any suggestions would be appreciated. I'll attach a photo of my bike rack as soon as I remember how.

Last edited by munly; April 9th, 2018 at 11:29. Reason: spelling
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Old April 9th, 2018, 07:59   #2
Join Date: Mar 2013
Location: Vancouver, BC, Canada
Fuel Economy: 40-42

Picture of bike rack...
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Old April 9th, 2018, 19:43   #3
Join Date: Jul 2016
Location: Vancouver

Bike rack will eat 50-100km to a tank on the highway pretty easily, drag is the square of velocity in m/s (110kph = double the drag of 80). I get 40-42mpg (5.6-6L/100) from north delta to the shop in my bew with 225 tires, should be able to exceed that in an alh.

Brake drag is another thing to check, I'd check coolant temp with a digital scanner too, my gauge will read 90 when I'm at 70-73.

Dealers - malonetuning.com/dealers
We made a free VCDS Log Viewer!

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Old April 9th, 2018, 22:21   #4
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Join Date: Aug 2005
Location: British Columbia
Fuel Economy: 4.6/5.6 - 5.3/6.7

Is the fuel temp sensor working properly? Check that and the coolant temperature with VCDS. When I had an ALH that went and created mileage about what you are getting. I used to get about 5.2 highway (45 usmpg) with an old Thule on old OEM racks running 105-110 indicated. Unless you drive with the bike up there all the time I think you should be doing better.
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Old April 10th, 2018, 06:59   #5
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Join Date: Feb 2017
Location: Denver (ex MN)
Fuel Economy: 35 to 50

Short trips and low ambient temp will keep your mileage around what you are getting. That is what I get here in MN in the winter especially when I have a lot of short trips. Every mile your engine spends not at 190f is lowering your mpg avg. My fuelly is around 44mpg as in the last year I have done about 7k miles in road trips at constant speeds. This is not representative of my mpg as a whole(42 is normal). I also have a Frostheater that I use in to help with warmup times. Check what Wilkins said too as I had a bad thermostat last summer and when it was cold I would not get to temp lowing my mpg.
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Old April 10th, 2018, 19:35   #6
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Join Date: Dec 2004
Location: Houston, Texas
Fuel Economy: 52/45/40

With just a roof rack without a bike I got a penalty of about 10 percent driving around. I would recommend you ditch the rack and put the bike inside. It will fit fine in the back seat area with the front wheel removed.
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Old April 14th, 2018, 18:31   #7
Join Date: Mar 2013
Location: Vancouver, BC, Canada
Fuel Economy: 40-42

thanks for the info everyone. the coolant temp was 90 degrees celsius when i was gathering data with VCDS. how do i check the fuel temperature?

also, this tank i have 300km with a little more than a quarter tank used. so the adjustments with the IQ and timing seems to be beneficial.

i'll report back when i burn though the whole tank. thanks.
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Old April 22nd, 2018, 19:23   #8
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Join Date: Jul 2014
Location: DFW, Texas
Fuel Economy: 45 mpg avg

I have your same car and have been frustrated hearing others getting better mpg than mine in the past. I had my turbo actuator replaced recently trying to cure the smoke at startup issue. It corrected the smoke, plus I got the unexpected bonus of an increase of about 5 mpg. A new acuator only costs about $115, so the payback is quick, its worth a try. I also have a roof rack with bikes and the 10% drop in mpg is about right when the bikes are loaded. Considering the high mpg these cars get I can’t complain about the drop in mpg with the bikes.
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Old April 22nd, 2018, 19:55   #9
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Join Date: Nov 2005
Location: VA/OH

short trips=low mpg, same with gas engines. roof rack won't help either. I went from driving mostly country to city driving and my mpg went way down.
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Old September 9th, 2018, 11:44   #10
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Join Date: Jun 2009
Location: Finland

Check your torsion value block 4 and idle fuel consumption block 15?.

Idle fuel consumption should be 0,4-0,6 l/h.
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