Seeking Advice to Improve Fuel Economy

gtroach

Member
Joined
Dec 25, 2009
Location
Shelbyville, KY
TDI
2006 Jetta 1.9L
Ok, I’ve been reading some of the posts and decided I needed to ask some questions of my own.

I purchased a 2006 Jetta TDI in March 09 with 29,500 miles on it. The car is closing in on 50,000 now. I purchased the car because I got transferred and it’s an 85 mile drive for me now to the office. The car is my daily driver so dependability, mileage and an easy ride are very important. This is my first VW and diesel and I'm really pleased with it. I’m getting 40-43mpg now but want to dial it up to around 50mpg.

The car is all stock with the six speed auto.
I’ve got new Copper CS4 tires and keep them inflated to 36psi.
The car has been serviced per the owners manual with oil changed every 10,000 (but I going to a 5,000 interval this next go)

I’m on well maintained state highways and interstate for the most of my commute. I set my cruise as often as traffic allows. I’m nearly always within five mph of the posted speed limit.

I don’t want to spend $1,000 to save $100 but know I will have to spend some cash and can expect to reap some savings.

I’m considering a K&N cold air intake right away and a new exhaust system with large pipe and a Magnaflow exhaust.

For those out there with experience, what are the PRO’s and CON’s of each of these options? Will it increase my mileage?
How hard is installation of the K&N?
Are there other items I should consider?
Are there items I should avoid?

Thanks much.:)
 

Plus 3 Golfer

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ARIZONA
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Und tschüss! 2009 Jetta 12/23/2012
Welcome. There are many threads on improving fuel mileage. Some say a mild tune while driving conservatively will increase mpg. Do the recommended maintenance (really no need for 5k oil changes) and go easy with your right foot both the go pedal and brake.


You have a CAI and your stock air filter and exhaust are just fine.
 

vdubJettaTDI_2010

Well-known member
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Dec 13, 2009
Location
Georgia
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2010 Jetta Sedan
I agree with 40x40, the Air Intake is not worth the money.

My example is I have one on my 06 Jeep. I really don't have that much of a boost in fuel economy, mainly horsepower for jeeping which eats fuel.

Plus, a Jeep Magazine, did a review of leading Cold Air Intakes, which was very humbling. Makes me want to take my Intake off sometimes.:(


Good luck with your TDI.
 

gtroach

Member
Joined
Dec 25, 2009
Location
Shelbyville, KY
TDI
2006 Jetta 1.9L
OK, after spending the last two hours looking at a myriad of threads, many of which seem to quote each other, it seems the concensus is the OEM intake and filter work pretty well. Well enough not to support the cost and effort to change.

For those using the scangauge, what are the top two benefits?

Is a mild tune a good second option?

Thanks
 

nicklockard

Torque Dorque
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Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
gtroach said:
OK, after spending the last two hours looking at a myriad of threads, many of which seem to quote each other, it seems the concensus is the OEM intake and filter work pretty well. Well enough not to support the cost and effort to change.
And the consensus is correct on this one. Aftermarket air filter setups are good for making nicer 'vroom vroom' sounds and nothing else on this platform.

gtroach said:
For those using the scangauge, what are the top two benefits?
1. Real-time diagnosis such as monitoring coolant water temps, as failed thermostats are quite common and can eat up 5-6mpg in winter, less in summer. I've diagnosed 2 failed ones that I would not have otherwise caught because the dash gauge lies badly, and I would not have had a reason to do a Vag-Log of CWT.

2. It teaches you what sorts of driving types and styles to stay away from in order to increase economy.

gtroach said:
Is a mild tune a good second option?
Yes, but for the cost it won't actually decrease your overall running expenses, but you can justify it to the significant 'other' because it actually helps FE for a given amount of (increased) driving fun :)


IMO, you should select a low rolling resistance tire in proper size/diameter for your vehicle when your vehicle is due for new tires. Keep in mind that your FE will go up as your newish tires (Coppers?) break in. FE always drops initially with new tires.
 

ruking

Top Post Dawg
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Location
San Jose area, CA
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2003 VW Jetta, 5 M, Reflex Silver: 09 Jetta, 6 Sp DSG, Candy White: 12 VW Touareg, 8 Sp A/T, Flint Gray
1. The best for your purposes is to remain stock.
2. Counter intuitively, the stock air filter filters better when it is so called dirtier b. do not open the air box to check, unless you are changing out the air filter. (you induce and increase the chances of silicon seal leakage).
3. I would stick with 10,000 miles OCI's. Even as I do 25,000 miles OCI's
4. K & N truly flows more dirt particles. It also increases the chances of MAF failure due to mineral oil contamination.
 
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chaloux

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Aug 15, 2007
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Gravenhurst, Ontario
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96 A6 Avant TDI Quattro, 04 Jetta Wagon
You also have to think about spending money to get better FE. How long is it going to take to make that $200 back from buying a SGII if you make it to 50mpg average?

My advice would be to use time instead. Find a tip that people commonly give and try it exclusively. How does it affect your MPG? If good, move on to the next tip. Of course, based on driving conditions and elements that are out of your control, you may need to evaluate a fuel saving method over a few tanks.

All that being said, I want maximum FE and my car is chipped and I upgraded my nozzles (a mild tune)... I will never gain that $550 back in fuel economy increases, but it sure does put a smile on my face.
 

chaloux

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Location
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96 A6 Avant TDI Quattro, 04 Jetta Wagon
Okay, I'll correct myself a bit. If you spend $250 and jump from 44mpg to 50mpg (consistently), and fill up twice a month, it'll take you almost two years to make that money back. NOT never ;)

Just sayin'.
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
quote from OP
"I’m on well maintained state highways and interstate for the most of my commute. I set my cruise as often as traffic allows. I’m nearly always within five mph of the posted speed limit."

Five mph on what side of the "posted limit"? And what is the posted limit??
Speed is the big thing in steady speed driving. Once you pass 60 mph, (probably lower in actuality)all other things being equal, you will come close to Ermie Roger's rule: For every 10 mph increase in speed you will loose 5% mpg. If you're getting 50 mpg @ 60 mph and increase to 70 you can expect 45mpg. Not actual numbers, but the percentages seem quite representative of what I have observed over 4+ years. Slow down and see the mpg's go up.
Tire pressure. 40+ psi makes for a noticeable improvement over 30 psi. You can tell the difference in one tank. Check them regularly.
Anticipate traffic conditions and/or your "flow". If the pack up ahead begins to stop/slow coast up to there to keep moving. Same with traffic lights. Slow down/coast up to them and keep moving whenever possible. Getting up to speed consumes the most fuel, so the idea is to keep it moving.
The Scan Gauge is a great tool for discovering what works/what doesn't, but it's very sensitive to any changes in your driving style/routine as well as any changes (Injection timing, quantity, etc) you make to the car if you mess around w/VCDS. I really like mine and wish I could afford one in every vehicle I own.
A "tune" or injector upgrade sometimes makes for better mpg, if you can restrain your right foot afterwards.
There are several excellant threads with lots of good tips in this section, you just have to search (I know, its not very good) and do a lot of reading. And the OP has an automatic, even though it's the six speed, its not a manual so don't expect too much.
One other thing-start keeping very accurate records of what mpgs you really get every fill. It lets you know trends, and none of this "I'm getting about XX-XX mpg". Then you know when you're improving, or not.
 
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ruking

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Location
San Jose area, CA
TDI
2003 VW Jetta, 5 M, Reflex Silver: 09 Jetta, 6 Sp DSG, Candy White: 12 VW Touareg, 8 Sp A/T, Flint Gray
As other have said, the next phase is to put some more factors in your favor. Not in any order but here are a few to kick off the discussion.

First off is to know what RPMS that your max torque and HP comes on, and the RANGEs. This is an RTF Manual exercise. Simply, the lowest RPMS giving you the max torque is one optimum point. So for example my max torque (#155 # ft) 2003 TDI is @ 1,750 rpms... to 2,250 rpms. While the use of the scan gauge can be more precise, you can use this knowledge to time after time make the best fuel usage decision for (the obscessive complusive minded) EVERY time; to not at all.

This has multiple threads and there is a size able skeptical audience, but higher TP is better than lower TP. I say start @ 85% of max side wall pressure and then adjust (for whatever reasons) . Since the two most common H rated tires are @ 44/51 psi max side wall pressure, we are talking (85% * 44/51) 37/38 psi to 43/44 psi. Again for example, I got 112,300 miles on a set of oem GY LS-H's (according to this thread and others a distant third rated and crappy oem tire) with 85% of max side wall pressure of 44 (38-36 PSI fronts and 38-34 rears) I of course would be more than interested to see how many folks got app 112,300 miles from the OEM recommendation of 26 psi TP or 59% of max side wall pressure.
 
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in2dwww

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USA
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2013 Passat TDI SEL, 2010 Jetta TDI Sedan 6MT - sold
You could go the Prius route and install the Jetta Lip spoiler, which supposedly reduces drag. My TDI came with the lip spoiler, and my MPG's are (probably) negligibly better.

But weight is the key issue. I would start with the wheels. Do you have 16" or 17" wheels? Are you running wider than the standard tire width?

One wild and wacky thing you might want to consider is replacing your stock rims with the wheel/hubcap setup from the Jetta S model. I haven't done this, but it's likely to reduce weight and give you a skinnier tire profile that will reduce drag. Don't forget about the spare tire - if you're really going for the gold, chuck that too and replace it with an inflatable temp doughnut spare.

Again, these are drastic measures that I wouldn't do, but they are worth mentioning.

Beyond drastic measures, you should consider driving style. Completely lift off the accelerator when traveling downhill. Lift off sooner when approaching stop signs and red lights. It sounds like easy advice to dish out, but in practice, it's impossible to abide by when in traffic.

In colder weather, I'm convinced that the air is denser and trying to find more MPG's in the winter is like trying to find the quarter in the fountain at the poor house. I have some tips on how to increase cold weather MPGs at:http://www.topgearage.com/?p=646

If I didn't need the back seats, I'd probably go so far as to remove the rear seat bottom cushion and headrests. Trim back every ounce possible.

You could also try adding some cetane boost to your next full tank. I found some in a gray bottle at my local auto parts shop. Only 4 ounces to 1 tank is supposedly able to increase cetane and increase lubrication in the fuel system. It's possible that the extra cetane over several tanks will make a difference.
 

donDavide

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Severna Park, Maryland USA
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2003 Jetta ;2006 Golf; 2015 Jetta S
All good info here. Also consider using a 505.01 instead of a 507.00, lots of info here even though this is not a fuel economy recomendation.
 

Blackbomber

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Wolcott, CT
TDI
2002 Automatic
Definately do not deviate from the 10K Oil change intervals. That is bad economy. Remember that VW specified your 10k interval before ULSD fuel was mandated in USA. Quite frankly, with the ULSD, you can go even further. I have been doing 15k, for over one year, and if you pull my valve cover, you could eat of the inside of my 167k engine.

After that, maintain your tire pressures (many recommend a higher pressure around 40psi or thereabouts) and drive with an eye on economy. Keep only the necesary junk in your trunk. Visit ecomodder.com for more info on hypermiling techniques.
 

billyz

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Location
Austin
TDI
2010 Jetta sportwagon tdi
I see it mentioned to run higher tire pressures. Like 40 psi instead of 35 psi.
I understand why this would decrease rolling resistance, but won't the tire wear out in the middle prematurely? Replacing tires should factor into the economy equation.
 

jettawreck

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Northern Minnesota-55744
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billyz said:
I see it mentioned to run higher tire pressures. Like 40 psi instead of 35 psi.
I understand why this would decrease rolling resistance, but won't the tire wear out in the middle prematurely? Replacing tires should factor into the economy equation.
Actually no it won't. My Goodyear Eagles have 80K miles on them and still have a good ways to go. Most belted tires won't be worn with some modest over-inflation.
 

in2dwww

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2013 Passat TDI SEL, 2010 Jetta TDI Sedan 6MT - sold
Actually, increasing tire pressure will create a harsher ride.

I've seen an AMG Driving Academy video that explains why Mercedes AMG cars run on very low tire pressure (27psi).

They created a demonstration with a German dude and two tires. One tire was at 27psi, the other was at 35psi. He was explaining that traction and control is reduced with the higher psi, and demonstrated this by picking up the 35psi tire and dropping it from 6 inches to a foot in the air. It bounced several times. Then he took the 27psi tire and dropped it from the same height. It basically hit the ground with a thud.

The demonstration was designed for AMG drivers - so that they get the maximum grip and handling by inflating to the proper psi.

If you inflate your TDI to 35psi, that's the ideal pressure to which the car was calibrated. If you go lower or higher, the ride quality will be affected. MPGs will also make a difference as well.

I always stick to the label on the door.

There is a video on the autonetwork, and I'll have to find it. Some man from Audi is riding around the back of a Q7 TDI explaining that VW/Audi did extensive testing in the US for the TDI and found that diesel fuel quality was absolute crap when compared to Europe. He said that minimum cetane in Europe is 52 and in the US, each station at any state had levels mainly around 35, but would fluctuate to the 40's and nothing was consistent.

Basically, quality diesel fuel is the issue at hand, not tire pressure.
 

in2dwww

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2013 Passat TDI SEL, 2010 Jetta TDI Sedan 6MT - sold
I found the video! This is 26 minutes long, and the audio gets scratchy for a few minutes, but it's worth the time. They talk about the Audi TDI, the research in the United States, and what they will do to improve MPG...

http://www.topgearage.com/?p=652
 

dclark

Veteran Member
Joined
Nov 27, 2005
I can think of two things that can help:
1) If you are using 5-40w, find a 5-30w that meets your specs. I am not familiar with your year car, so I don't know if that applies.
2) Get Mich Energy a/s tires when your cooper tires are worn. These will give anywhere from 2-4 mpg improvement. I have them and like'em.
 

Blackbomber

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Location
Wolcott, CT
TDI
2002 Automatic
Bias ply tires will develop center wear with overinflation. Radials do not. A wide tire (such as AMGs are equipped with) will require less pressure than a narrow one, since the weight is distributed across a larger surface. More square inches = less pounds per square inch to support the same weight. Not really apples to apples, but I will check out that vid. I'm sure I'll learn quite a bit. Yes the higher PSI will create a harsher ride, no doubt. I used to run 42psi (for quite a while). I found almost no difference in economy between 35psi and 42 on my ALH Automatic with stock 195/65/15's, so have gone back to factory recommended pressures. I didn't mind the harsh ride, but I felt wet road traction was comprimised. I mainly wanted to stress that the pressure should be monitored. It changes with ambient temperature, and a LOWER than recommended pressure will increase comsuption as well as cause tires to wear prematurely.
 

nicklockard

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Location
Arizona
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SOLD 2010 Touareg Tdi w/factory Tow PCKG
Blackbomber said:
A wide tire (such as AMGs are equipped with) will require less pressure than a narrow one, since the weight is distributed across a larger surface. More square inches = less pounds per square inch to support the same weight.
Wrong. The footprint in square inches is the same no matter what tire widths you run. It is determined by the weight of the car and nothing else. With wider tires, your tire contact patch is shaped more like:



__________________
|...|....|....|....|....|..|
|...|....|....|....|....|..|
|...|....|....|....|....|..|
___________________


Whereas a narrower, higher profile tire's contact patch is shaped like:

_____________
|....|....|....|...|
|....|....|....|...|
|....|....|....|...|
|....|....|....|...|
|....|....|....|...|
_____________

but both have same area, just different shapes.

Oh, and gtroach, check out this great Tire Rack review of fuel economy tires:

http://www.tirerack.com/tires/tests/TireTestServlet?tireMake=Michelin&tireModel=Energy+Saver+A/S

Personally, I'm going to mount a set of the Yokohama dB super E-spec's in 195/65 to my 318ti next week.

 
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donDavide

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When I pumped up my Tires after listening to the Hypermile dude ( I am refraining from name calling) at 2008 TDifest I got worse mile and my trip was mostly down hil on the way back. A my opinion on Michilens is overpriced and overrated and switching to 5w-30 from 40 will not yield that much difference at all. Been there nad done that.
 

Blackbomber

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Location
Wolcott, CT
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2002 Automatic
Nick, cite your sources, if you don't mind. I have heard the same as what you said, but in the context of motorcycle tires. More accurately, the section of an MC tire really doesn't contribute much to the contact patch. For autos I have read both, so am going with what seems correct to me. I would think that if the diameter of two different tires is equal, the length of the contact patch would be the same regardless of width.
 

nicklockard

Torque Dorque
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Arizona
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SOLD 2010 Touareg Tdi w/factory Tow PCKG
Blackbomber said:
Nick, cite your sources, if you don't mind. I have heard the same as what you said, but in the context of motorcycle tires. More accurately, the section of an MC tire really doesn't contribute much to the contact patch. For autos I have read both, so am going with what seems correct to me. I would think that if the diameter of two different tires is equal, the length of the contact patch would be the same regardless of width.

My source is college physics 211. Actually you can learn this in HS physics text too:

Pressure is force/area. Force is mass*acceleration. In this case acceleration = 9.81 ms^-2 also known as 'g'.


So pressure is then

......(mass of car)*g
________________________
....area of contact patch

Since g is a constant and the mass of your car is constant then that mathematically forces the contact patch area to remain a constant. Only the shape changes. Put another way: the downward force imposed by Earth's gravity is the same no matter what size/profile tire you have mounted. Low profile tires have more width so they handle side-to-side forces better (more rubber to resist sliding). But they also poke a larger hole in the air and add to aerodynamic drag.
 
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Windjammer

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Cinti, OH
TDI
MK4 & Mk5
nicklockard said:
Since g is a constant and the mass of your car is constant then that mathematically forces the contact patch area to remain a constant.
Not exactly. Try putting 5psi in your tires & then 50psi tell us if the contact patch area is the same.
 

nicklockard

Torque Dorque
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Aug 15, 2004
Location
Arizona
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SOLD 2010 Touareg Tdi w/factory Tow PCKG
Who said anything about stupidly under-inflating your tires?
:confused:

If you had reading comprehension you would be able to tell the discussion point was begun when Blackbomber asserted: "A wide tire (such as AMGs are equipped with) will require less pressure than a narrow one, since the weight is distributed across a larger surface. More square inches = less pounds per square inch to support the same weight."
I pointed out that it wasn't true. I neglected to state every obvious thing like you don't change pressures between the two examples. The comparison/contrast was between tire aspect ratio's not between different inflation pressures. But methinks you're more interested in comparing weenie sizes.

Troll.


For anyone interested in improving fuel economy, follow the link in my signature to Tire Rack's recent review.
 
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Blackbomber

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Wolcott, CT
TDI
2002 Automatic
Nick, thanks for the response. It's been a LONG time since I studied technical college physics (still have the textbook, though). Your explination is logical for a given vehicle, but contradicts what many people (obviously including myself) have been taught from an automotive perspective. Perhaps I had it backwards, and the lower tires create the larger contact patch, instead of the larger patch requiring lower pressures. I think I need to spend some more time to wrap my mind around it, though. I'll clam up until then.
 
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