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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 July 30th, 2016, 18:11   #226
TDIFan1989
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Okay, sorry for spaming this post with other things but I did have a strange thought bubble.

How would battery quality/alternator performance affect your fuel economy? Would it affect fuel economy? I ask because in addition to my other upgrades, I changed my old battery due to starting issues and am thinking it may have also factored into my increased MPG.
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Old February 12th, 2017, 20:31   #227
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Great info! Love the "Italian Tune up"
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Old February 17th, 2017, 16:13   #228
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Quote:
Originally Posted by oilhammer View Post
I've put this together in an effort to help some folks diagnose what may be a loss of fuel economy (MPGs) with their TDIs. Keep in mind, many of these items can work against your car in concert to add up to a sizeable increase in fuel consumption over time, so please don't dismiss any one item because it may be just one small part of the puzzle, but an important part nonetheless!

Tires: this goes beyond simply air pressure, although that is an important part. Tread design is another, as well as the proper size and load rating. When in doubt, look at your car's tire information placard. It will have the proper size, load, and speed rating. Going from the proper 91 load to an 89 (an all too common mistake) can take a 1 MPG hit all by itself over the same model tire. Low Rolling Resistance (LRR) tires are becoming more popular, and are usually marketed as such. Still, keeping the pressure up, and the rating correct, is very important.

Alignment: if the alignment of the car is off, the tires can 'scrub' as they roll down the road. This causes excess friction and drag, which causes the engine to have to work harder. Checking the alignment with proper equipment is the only way to be sure everything is in specification. Worn bushings and steering components can cause the alignment to be out.

Trim pieces and shields: the car was designed to be both slick on the top AND the bottom. Missing shields under the car can not only make the engine take longer to reach operating temperature, they can also cause extra wind resistance when travelling down the road, and the faster you go, the worse it becomes. Missing grill inserts, missing lower splash shields, missing/damaged fender liners, can all contribute to this problem.

Thermostat: if the engine cannot reach proper operating temperature as quickly as possible and maintain it, it will cause more fuel to be used. Don't assume the gauge (or light in the New Beetle and latest Jetta sedan) is enough to tell you the engine coolant is warm enough. The only sure way to know is with a scan tool and watching the coolant temp data. Thermostats don't last forever, and one that cannot do its job properly needs to be replaced. If it gets really bad, the engine controller will flag a fault, however it has to be pretty bad before that happens.

Timing: Both the VE TDI and the PD TDI are sensitive to timing. Just a few degrees can make a substantial difference. If the timing belt was installed wrong, your timing will be off. Period. While there is some sliding scale here, as some timing settings favor power over economy, keep this in mind when you set the timing after the belt is installed.

Air cleaner/air flow sensor (MAF): these items need to be in proper condition, and work in conjunction with the Exhaust Gas Recirculation (EGR) for proper engine function. A little bit off, or dirty, or poor quality/fitment can cause some adverse performance.

Lambda (oxygen) sensor (PD only): these can degrade and cause a slow response from the ECU in a similar (but not identical) fashion that a gasoline fueled car can, and can cause some loss of fuel mileage on PDs.

Intake/EGR clogging: while not the issue it once was, due to ULSD fuel, it is still something that should be checked for, especially on VE cars. This can cause a loss of power overall, and call for excessive fuel use since the air the engine needs to run cannot get in properly.

Brakes: many Volkswagens, especially A4 platform cars, have chronic stuck parking brake cables. This causes the rear calipers to drag, and your torquey diesel won't know it... it 'll just eat more fuel to move the car down the road. Also, brake pad perches can rust up, and cause the pads to sieze in their spots, dragging the brakes.

turbocharger: the "T" in "TDI" can't work properly if there is a vacuum/pressure leak, binding VNT/wastegate actuator, etc. While a fault will be flagged if it gets really bad, low boost can slowly creep up and rob you of both power and fuel economy gradually without you even knowing. Again, a scan tool checking requested and actual boost can help check the condition of your turbocharger system.

Driving style: we hear this all too often here, but it bears repeating here. Driving the car too easy for too long can really mess things up in the MPG department. Keeping the pipes clean, by occasional spirited driving, can help to keep the EGR clean, the intake clean, the intercooler clean, the breather system functioning properly, and the turbocharger working correctly, in addition to keep the catalyst and (where equipped) Diesel Particle Filter (DPF) clean and in good working order. A good test on VE and PD cars is to do a floorboarding rolling start (once the engine is warm) and see if it belches out a cloud of black smoke. A healthy, happy TDI, even a mildly modded one, should NOT do this. If it does, and it goes away after doing this a few times, you know you were driving it too easy for too long. Some folks call this an 'Italian tune up'. Whatever you want to call it, it works.

Excess weight: we can call this a minor one, but let's face it, dragging 50 pounds of tools, a stack of bricks, your entire CD collection, your golf clubs, the collected works of Charles Dickens, and 70 bottles of water around in your car is not really necessary.

Hopefully some of the above listed items can help you track down a possible loss of fuel economy!
I prefer the diaries of Anais Nin thank you.....

But seriously, an excellent posting here fellas [and ladies]!!!
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Old May 22nd, 2017, 12:16   #229
2015vwgolfdiesel
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Originally Posted by applejacks View Post
I drive a 2014 Jetta DSG and there was a day when I couldn't get over 450 miles on a tank to save my life. Now I'm bummed out to not hit 525 and once I get my Green Diesel tune on the car, I fully expect to regularly hit 600 miles per tank. Once you really start paying attention to how you drive, you will begin to achieve better fuel economy. There really is an art to it.

-Limit your idling. Don't start your car until your seat belt is on and your things are situated in the car. I usually put it in gear about 30 seconds after I start the car.

-Plan your route and stops. For me, there are 3 ways for me to go to work. Once I changed my route a little, I saw an increase in mpg because of the other things that also fell into place.

-Look far ahead and anticipate. If you drive the same route to work, you will learn patterns. You will learn if you go x speed, you can hit the lights, or you will know that a red light will be coming up. Coast to the red light.

-Be 'that guy' who drives the speed limit and stay in the right lane so people can go around you. If you are coasting to a stoplight, let others go around you. Be ready for the dreaded stare at the red light, because you will likely see the person who flew around you at the stoplight sitting next to you.

-Unless you have a lot of downhills, the cruise control is your friend. Use it all of the time and learn how to play with it. This will be argued, but it has helped me a good bit.

-Use drafts, let the car in front of you move the air.


-Keep your car in great shape. Some people will use the max psi on the sidewall of the tire, I just use the factory recommended PSI as indicated by the door placard. I also use 6-8oz of Power Service additive every other fuel up. Little air dams and such that tend to begin to sag need to be zip tied or screwed back up. Also, if it doesn't belong in your car, don't keep it in your car. Weight is key here and it all adds up.

-Use the meters in your car. The real time MPG and the average MPG I have found to be fairly accurate. I keep my display set to average MPG and try to get it as high as possible on every trip. I also reset my trip odometer at every fill up so I can watch my miles climb.

These things might not mean much, but they all add up and will cost you nothing to do. If you really pay attention to your driving, your MPG will increase and achieving better fuel economy will soon become a game. Also, keep track of your fuel economy on paper, fuelly, or an excel spreadsheet.
Great post, but for the drafting. In my youth, it cost me a windshield.

From memory it might have been my 1956 Chevy
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Old May 28th, 2017, 18:35   #230
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[QUOTE=mohawk69;5072659]"I would suggest it is impossible to get 60 mpg out of any diesel car on a 3.8 liter US gallon and not many would make it on a 4.54 liter imperial gallon."
Wrong, wrong, and wrong. I've a 2003 TDI Jetta manual transmission. Here in Texas there is no diesel emission requirements. So. . .I defeated the EGR. This eliminates carbon buildup in the intake manifold. I also put 1/4 oz of straight (non additive) 10w oil per gallon with the fuel. This raises the cetane of the fuel. I look ahead to minimize the use of my brakes. I try to minimize the use of the A/C but in the summer in Texas that is a tall order. I've 146,000 miles on the car. My overall fuel economy for all 146,000 is 54.8 mpg. Speed eats into fuel economy. I once drove from Sedona, AZ to Austin, TX (1122 miles) on one tank of fuel to prove it could be done. That was 68.5 mpg.
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Old May 28th, 2017, 22:05   #231
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JW, that was an amazing feat of FE, I have to ask how fast were you driving?
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Old May 29th, 2017, 17:47   #232
2015vwgolfdiesel
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Exclamation Use drafts, let the car in front of you move the air. NOT

Out today for a city drive, and one store stop for "goodies."

On the first leg, using the inter-city free ways, (with speed limit at 60 MPH ~~ I was going 65) ~~ a fast mover passed me on left at approx 90. He/she moved directly in front of me, (one of the center lanes)

Then a really fast mover did the same from my right side. He/she also moved directly in front of me, and was over taking car number one.

Car number one blew a tire. All I could see was smoke (about 1.5 seconds) and then flying tire alligators.

Car number one did a hard left one and a half lane side motion, then hard right, crossing approx 2.5 lanes, then hard back left, then hard right again before being able to slow down (any) and get it off the right shoulder, at about 40-ish.

Car number 2 seemed fully in control, but hit the brakes full. More smoke.

I have always driven with a close eye on rear traffic; so I was in full forward attention, knowing I had no rear (or side) worries. All I had to do was watch the alligators. No deviation from straight forward was appropriate.

At 5 mph over the speed limit, that's all the consideration I care to give moderate speeders or hyper speed city folks

Speed kills

Hyper speed (with weak tires) is nuts X 10
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Do the fix, pocket $8,000-ish 6, 776 miles on the clock, Pristine condition
BB = $25,625, but VW is not paying for PRIME condition nor ULTRA low miles.
Net bases in my 2015 Golf = $12,495
NADA-KBB for older CPO Golf TDi 2014 = $18,250
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Old May 30th, 2017, 07:47   #233
2015vwgolfdiesel
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Quote:
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..... snip....
Driving style: we hear this all too often here, but it bears repeating here. Driving the car too easy for too long can really mess things up in the MPG department. Keeping the pipes clean, by occasional spirited driving, can help to keep the EGR clean, the intake clean, the intercooler clean, the breather system functioning properly, and the turbocharger working correctly, in addition to keep the catalyst and (where equipped) Diesel Particle Filter (DPF) clean and in good working order. A good test on VE and PD cars is to do a floorboarding rolling start (once the engine is warm) and see if it belches out a cloud of black smoke. A healthy, happy TDI, even a mildly modded one, should NOT do this. If it does, and it goes away after doing this a few times, you know you were driving it too easy for too long. Some folks call this an 'Italian tune up'. Whatever you want to call it, it works...... snip....
Hi oilhammer

As I am a "consecutive" driver, I am at risk of driving too easy too long.

On a few-several occasions I did (and do) "dynamite" the ol' girl. So far so good. No smoke at all.

I only do this at a time where traffic is low; and pick locations where I feel there will be no Police watching as I move quickly to 80-ish, and then brake back to legal

Then repeat. as needed to be sure

Again, Thanks
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Do the fix, pocket $8,000-ish 6, 776 miles on the clock, Pristine condition
BB = $25,625, but VW is not paying for PRIME condition nor ULTRA low miles.
Net bases in my 2015 Golf = $12,495
NADA-KBB for older CPO Golf TDi 2014 = $18,250
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Old May 30th, 2017, 19:35   #234
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JW, that was an amazing feat of FE, I have to ask how fast were you driving?
47 mph maximum. I coasted down all hills of course and sometimes the speed got much higher while coasting. It was August and I used no A/C. Oh baby it was miserably hot. However as I said it was a one time stunt to prove it could be done.
Speed and wind direction eats into FE. If I never exceed 55 mph I can always exceed 60 mpg. If I'm on I-10 (80 mph) with the A/C blowing the mileage drops to a horrific 48 mpg.
One more point. With new tires my odometer reads about 2.6% low. In other words if I role up 100 miles I've really gone 102.6 miles. As the tires wear this inaccuracy decreases.
I'm convinced the ALH is the best diesel VW ever made. It is a shame it's not made anymore.
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Old August 17th, 2017, 13:15   #235
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68.5 mpg? What did you do--remove all the seats, cover the wheels with cardboard, inflate the tires to 70 psi? I'm struggling with that. My wife and I drove from Wythville Virginia to Oshkosh, Wisconsin on one tank of fuel in our 2004 Jetta TDI Station wagon with a five speed. With a side trip into Milwaukee the total distance was 805 miles. I kept my speed in the 65 to 70 mph range with the ac on at times. 800 miles on a tank was a goal for me and I really filled the tank in VA. We just bought a 2015 Golf Sport Wagon TDI with a 6-speed and got 53 mpg on our first tank. Planning on a trip to WI in September and hope to improve on the FE.
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Old August 17th, 2017, 13:19   #236
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If you hypermile and do some really kinda dumb things you can get some crazy high MPG. But they are generally unrealistic figures because they are achieved under and unrealistic set of circumstances.

I got 61 MPG out of my modded '98 Jetta TDI at 2002 TDIfest, but I drove it in a manner that I would not normally drive. Not even close, LOL. And to be real truthful, it was miserable. Especially considering the same car, driving "balls out", would hit 50 easily.
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Old November 3rd, 2017, 14:02   #237
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In my ALH with a big turbo and nozzles with the A/C on and doing 80 MPH, 48 MPG would never be considered "horrific, I would consider that quite the gift. I spend 99% of my time driving in town, and if I am really careful I can get Torque Pro to tell me 44-45 MPG but that is driving 35 MPH in 4th gear.
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Old November 4th, 2017, 18:26   #238
1.9ZOOK
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Would bumping the IQ number up a bit,say from 3.2 to 3.8 change the milage much?
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Old November 27th, 2017, 05:52   #239
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Quote:
Originally Posted by oilhammer View Post
.... snip.....
Driving style: we hear this all too often here, but it bears repeating here. Driving the car too easy for too long can really mess things up in the MPG department. Keeping the pipes clean, by occasional spirited driving, can help to keep the EGR clean, the intake clean, the intercooler clean, the breather system functioning properly, and the turbocharger working correctly, in addition to keep the catalyst and (where equipped) Diesel Particle Filter (DPF) clean and in good working order. A good test on VE and PD cars is to do a floorboarding rolling start (once the engine is warm) and see if it belches out a cloud of black smoke. A healthy, happy TDI, even a mildly modded one, should NOT do this. If it does, and it goes away after doing this a few times, you know you were driving it too easy for too long. Some folks call this an 'Italian tune up'. Whatever you want to call it, it works. )
....well the chickens have come home ~~ me thinks

... this ol' gezzer gentle-slow-moderate TDi driver drove over to see Mom yesterday expecting 55-ish MPG on the dash idiot gage. 156 miles round trip.

.... middle part of the 13.2 gallon tank

..... was expecting 55-ish MPG ... Out side temp = 65-ish

.... 47.9 MPG ~~ Only one note was a 10-15 minute construction delay with car at idle --- watching the idiot it did not drop THAT much.

..... wonder how much Italian foot this Irishman needs to help get it back.
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Do the fix, pocket $8,000-ish 6, 776 miles on the clock, Pristine condition
BB = $25,625, but VW is not paying for PRIME condition nor ULTRA low miles.
Net bases in my 2015 Golf = $12,495
NADA-KBB for older CPO Golf TDi 2014 = $18,250
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Old December 30th, 2017, 06:03   #240
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Anyone do a EGR delete on a 1999 1.9TDI and there fuel MPG drop in half???? I use to get 1000 kms to one tank of fuel and since i took my EGR valve out and put in the race pipe now i'm only getting 500 kms?? This is my first tank of fuel but doubt its going to improve.
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