Newbies and Vets: Tips for better fuel economy!

ruking

Top Post Dawg
Joined
Mar 27, 2003
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
Since the poster has a 2010 TDI/DSG, perhaps the best advice is to accelerate between the max torque rpm range: 1,750 to 2,500 rpm. Why? The maximum torque range just happens to be where the TDI is the most efficient.

Now I do not personally do this on a 09 TDI with DSG, but I am ok with the current range of 40-47 mpg, till it breaks in between 30,000 to 60,000 miles. At that point it will be at max PSI and the mpg will be @ the best.
 
Last edited:

Fuz

Member
Joined
Jun 29, 2010
Location
Apex, NC
TDI
2005 Passatt TDI
FUZ and plap - welcome to the club!
Keep the car in gear, the ECU cuts fuel when you don't have your foot on the accelerator, which means you're using no fuel at all when you're going down the hill.


-BB
Thanks BB,
What I have noticed is a significantly decreased engine drag when I shift into neutral though...making it easier to maintain speed or even continue accelerating while in neutral on downhills. I just wonder if it's hard on the tranny.
 

ruking

Top Post Dawg
Joined
Mar 27, 2003
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
Thanks BB,
What I have noticed is a significantly decreased engine drag when I shift into neutral though...making it easier to maintain speed or even continue accelerating while in neutral on downhills. I just wonder if it's hard on the tranny.
The real question is why would you want to put it in neutral when it is designed to stay in gear? This is assuming of course you have an automatic.
 

Fuz

Member
Joined
Jun 29, 2010
Location
Apex, NC
TDI
2005 Passatt TDI
The real question is why would you want to put it in neutral when it is designed to stay in gear? This is assuming of course you have an automatic.
Yes, it's an automatic. The reason for shifting to neutral is that I can feel the reduction in drag from the engine in gear. I can achieve higher coasting speeds downhill in neutral than when in Drive. I've seen in other posts that the engine consumes less fuel in neutral (such as at a stoplight).
- Fuz
 

ruking

Top Post Dawg
Joined
Mar 27, 2003
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
I have not studied the comparisons and contrasts of how a TDI in Passat vs Jetta's (03/09 in my case) works, but the reverse is true. (I have manual/ DSG so NO automatic but it is true for man/DSG aka no fuel draw in gear or D/S) Off throttle coasting in D creates a " no fuel" draw situation. You might not notice it tank to tank but cummulatively the idle time in neutral does add up.
 

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
Yes, it's an automatic. The reason for shifting to neutral is that I can feel the reduction in drag from the engine in gear. I can achieve higher coasting speeds downhill in neutral than when in Drive. I've seen in other posts that the engine consumes less fuel in neutral (such as at a stoplight).
- Fuz
The simple answer is you will use less fuel if you shift into "N" @ stop lights and where you can coast farther than staying in gear . IF you can coast just as far by staying in gear , like going down a grade that will make you gain too much speed then staying in gear is the way to go .

If there are a lot of stop lights shifting into "N" can save quite a bit of fuel . This also reduces built up cooling system & trans heat , wear inside of the trans by reducing wear & friction
 

Tom Servo

Veteran Member
Joined
Jul 9, 2000
Location
LA (Lower Alabama)
TDI
2005 Gol TDI, blue and falling apart
Is there any advantage/disadvantage to shifting into neutral to coast down some hills on country roads? Am I impacting the transmission?
If there are a lot of stop lights shifting into "N" can save quite a bit of fuel . This also reduces built up cooling system & trans heat , wear inside of the trans by reducing wear & friction
I'm curious. The way I read Fuz's question, it sounds like he would be shifting into Neutral to coast downhill, but that doesn't mean he will necessarily be coasting to a stop. That means putting the transmission back into Drive while the wheels are moving at a considerable speed.

So I have to ask, can that harm the transmission by shifting into Drive at highway speeds? I've never owned an automatic transmission so I dunno how they act. I have shifted some autos into neutral at speed and back into drive and one (a Ford) seemed to shudder pretty harshly, while a GM truck was smooth as butter, kind of rev matching to the highest gear for smoothness.
 

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
While I wouldn't suggest doing it if you aren't pushing on the throttle when you re-engage the trans , shifting in or out of "N" should be no more stressful than just staying in gear .

These aren't mechanically shifted transmissions , those could be pretty unhappy if you did this . The computer that controls the trans uses a speed sensor & throttle position to decide which gear is appropriate for the given speed . They design the trans to handle being shifted into & out of "N" with ease which is why the button isn't required to be pushed to do so . So going down the road @ say 60 and you shift into "N" then back into "D" will shift you into the appropriate gear then re-lock the torque converter . The old VW/Audi E-mode automatic could do this with ease .
 

Fuz

Member
Joined
Jun 29, 2010
Location
Apex, NC
TDI
2005 Passatt TDI
I'm treating this Automatic much the way I treated my manual, and I'm not sure that's ok, which is why I'm asking.
You are correct that I shift into N at highway speeds and then back into D after coasting down a long hill. Mostly I do this on country roads. I normally do not press the throttle while re-engaging.
I've heard various answers by folks about what consequences this can have, and I'm wondering if anyone on here has experience with it.
Fuz
 

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
I'm treating this Automatic much the way I treated my manual, and I'm not sure that's ok, which is why I'm asking.
You are correct that I shift into N at highway speeds and then back into D after coasting down a long hill. Mostly I do this on country roads. I normally do not press the throttle while re-engaging.
I've heard various answers by folks about what consequences this can have, and I'm wondering if anyone on here has experience with it.
Fuz
As long as you are not slamming the power to it while shifting back into gear "D" It should be no more stress on the internals than regular shifting , automatic & manual . Is that the answer you are looking for ??

How does it react to you doing this ?? Does it seem to search for correct gear to match your speed or does it just go back into high gear ????
 

Fuz

Member
Joined
Jun 29, 2010
Location
Apex, NC
TDI
2005 Passatt TDI
That is the answer I was "hoping" for. Some folks whom I would not consider mechanics advise that it is bad bad on the tranny.

The vehicle reacts pretty calm when I drop it into D from N.
Here's an example of how I've handled it: In my daily commute I get to one stoplight that is at the top of a long hill heading into swift creek basin. If the light is green when I get there and I'm doing 40-45 mph, I let off the accelerator and drop it into N. The RPMs drop and you can feel the gears release and the subsequent reduction in drag. The car can easily maintain speed and even accelerates near the bottom of the hill until I'm doing ~ 55mph. Once I get on the flats, I drop it back into D - it feels like it's going into the highest gear. I watch the rpm ease back up and then gently start on the accelerator again.
If I leave the car in gear while going down the same hill I notice that it doesn't roll as easily down the hill. I take that to be the natural drag that being in gear causes.
This whole thing is of course about eeking out the best MPG for economy sake. And it would not be economical to eff up the tranny.
 

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
That is the answer I was "hoping" for. Some folks whom I would not consider mechanics advise that it is bad bad on the tranny.

The vehicle reacts pretty calm when I drop it into D from N.
Here's an example of how I've handled it: In my daily commute I get to one stoplight that is at the top of a long hill heading into swift creek basin. If the light is green when I get there and I'm doing 40-45 mph, I let off the accelerator and drop it into N. The RPMs drop and you can feel the gears release and the subsequent reduction in drag. The car can easily maintain speed and even accelerates near the bottom of the hill until I'm doing ~ 55mph. Once I get on the flats, I drop it back into D - it feels like it's going into the highest gear. I watch the rpm ease back up and then gently start on the accelerator again.
If I leave the car in gear while going down the same hill I notice that it doesn't roll as easily down the hill. I take that to be the natural drag that being in gear causes.
This whole thing is of course about eeking out the best MPG for economy sake. And it would not be economical to eff up the tranny.
Then the wear could actually be less for miles traveled over the life of the trans . You are doing what the E-mode automatic of the 80s did automatically to improve lower speed stop & go travel . On that old design there was a lot of lost energy that was recovered by doing this . Your trans is many times by a factor of 6-10 times more efficient so there is less to be gained by doing this . But there should still be at least a couple of mpgs to gained from doing this .

I owned two VWs , Quantum TDs and 3 Audi 5000TDs that did this over the years . On all they could make as much as a 12 mpg difference from staying in D or using E . In D the cars would get ~28-30 mpgs pretty consistantly . In E they could break 40 mpgs on lower speed city loops going in & out of gear automatically .
 

jpv

Member
Joined
Sep 12, 2010
Location
alberta canada
TDI
2005 passat gls wagon
As far as im aware, soilers are designed for race cars. The spoiler creates down force which gives the car better traction in the corners thus allowing them to go around the corners significantly faster. The down side is that they creat huge ammounts of drag in the straights. F1 car now have a device that allows air to go thru the car and behind the spoiler to reduce the huge ammounts of drag they create in the straight line where high speeds are common. When they get to the corners they turn off the device and once again huge ammounts of down force are created for the faster cornering speeds. When honda attempted a record speed run with a F1 car they removed the spoilers for a faster straight line run. Spoilers are in effect a huge negative factor when it comes to fuel milege. The look cool factor has however taken over and a lot of cars now have spoilers. Spoliers for hatch back cars are effective in keeping the rear window cleaner as they direct clean, fast moving air from the top of the vehicle down the back of the car thus air washing the window which doesnt allow debris from the turbulent air to hit and stick to the rear window. Its effectiveness is however debatible. The best thing for fuel milege is to keep things as clean and free of items as possible such as roof racks. One interesting note is that myth busters made a car shell that was dimpled like a golf ball and obtained a 11% increase in fuel milege........
 

torino68

Member
Joined
Dec 20, 2009
Location
Virginia
TDI
04 Jetta PD
Actually rotarykid, you're wrong. It adds more wear to the clutch because you're dragging the engine from 0 rpms up to 2,000 or 3,000 rpms, depending on your current cruising speed. If you left the engine running with it in neutral, you could rev-match with the throttle to reduce clutch wear, or you could just cruise in gear and put absolutely no wear on the clutch.
And don't forget the stress on that timing belt by pushing the vehicle to start your engine
 

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
And don't forget the stress on that timing belt by pushing the vehicle to start your engine
What extra stress ??? The engine crank turns the T-belt system the same if pushed by the trans while in overrun , turned by the pistons when power is applied , using the momentum to start the engine or by the starter or while shifting gears going up or down through the pattern .

All involve the engine turning in one direction & changes in rpm

:confused: No difference what-so-ever on what the cause was :confused:.
 

kevinp

Active member
Joined
Mar 24, 2010
Location
Las Vegas
TDI
2004 Jetta tdi
Will using good fuel really help increase my gas mileage? I use a generic fuel but I've seen the same fuel truck at shell stations so I don’t think it's too bad. The best mpg I've seen is a little over 40, no where near everybody’s 50mpg. I always check tire pressure and drive mildly and the air filter looks good. Would a new fuel filter help? I know having a pd doesn’t help. I have 67k and a 5spd. Any suggestions??

Kevin
 

Tom Servo

Veteran Member
Joined
Jul 9, 2000
Location
LA (Lower Alabama)
TDI
2005 Gol TDI, blue and falling apart
Kevin I will be of no help to you but I gotta offer this anyway… I swear the worse the fuel the better my mileage is. If it's smokin' at every stop light, the mileage usually winds up being somewhere north of 47 MPG. And strangely, power seems to be better, too.

Dunno why. B20 biodiesel is where I usually get my lowest mileage, but there's little to no smoke.

:confused:
 

CStone

Veteran Member
Joined
Apr 12, 2006
Location
East TN
TDI
2003 Jetta ALH 5sp.
To all you neutral coasters:

I used to do that (kick car into neutral on long downhills), especially on the way home from my former job. One hill in particular, I could reach 80+MPH by the bottom of the hill and coast quite a long way before I slowed back to 55MPH and put the car back into gear. Other hills on the way home allowed 1+ miles of coasting as well.

Two things made me stop:

1. Didn't really see any MPG improvement over driving normally.
2. THP was sitting at the bottom of the big hill I mentioned above and I received a Fast Driver Award totalling $182 as a result.
 

brucetmoose

Veteran Member
Joined
Jan 20, 2006
Location
Rochester, NY
TDI
Used to own a 2002 Jetta TDI - Black/Black
Further question about manual shift points

Besides accelerating slowly, shift points (in a manual) are important, too. A lot of people seem to believe you should shift as soon as you can without lugging the engine. I'm not sure driving that conservatively is a good idea for the turbo, 100% of the time, but you definitely don't wanna creep up in speed while staying in the same gear.
Tom;

I was shifting at 1900 to 2000 on my 2002 because it said that was the peak torque point. I'm curious to know from you and/or the expertise of the group if that was too low. I always got about 42 to 46 around town and 50+ on the wonderful NY State Thruway.

Even though I don't have it anymore, I'm trying to get a used one.
 

Tom Servo

Veteran Member
Joined
Jul 9, 2000
Location
LA (Lower Alabama)
TDI
2005 Gol TDI, blue and falling apart
Tom;

I was shifting at 1900 to 2000 on my 2002 because it said that was the peak torque point. I'm curious to know from you and/or the expertise of the group if that was too low. I always got about 42 to 46 around town and 50+ on the wonderful NY State Thruway.

Even though I don't have it anymore, I'm trying to get a used one.
I don't think it's too low for economy shifting, but I'm no expert on any of this. The point I was trying to make was that the engine needs 'exercising' occasionally. That and, I think it's a waste of fuel to run each gear up to, say, 3000 RPM if you're taking a long time to get there.
 

rotarykid

Top Post Dawg
Joined
Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
TDI
1997 Passat TDI White,99.5 Blue Jetta TDI
To all you neutral coasters:

I used to do that (kick car into neutral on long downhills), especially on the way home from my former job. One hill in particular, I could reach 80+MPH by the bottom of the hill and coast quite a long way before I slowed back to 55MPH and put the car back into gear. Other hills on the way home allowed 1+ miles of coasting as well.

Two things made me stop:

1. Didn't really see any MPG improvement over driving normally.
2. THP was sitting at the bottom of the big hill I mentioned above and I received a Fast Driver Award totalling $182 as a result.
On every time I've ever advocated coasting in "N" I've made sure I note that this should not be , never be done in situations where excessive speed is built up ! If you only do this in situations like you describe you are likely not to see that much improvement , maybe one or two mpgs over a tank if you don't hammer the power in to keep speed going back up hill . If you hammer the power in to keep speed going up hill you will not see much if any gain , maybe a little lose of mpgs if you really push it going up hill or wait too long to get back on the power .

And on not gaining any mpgs if done properly , I call bullsh!t ! . On every car I've ever done this on I gained at least a couple of mpgs , 3-5 minimum over a tank where this is done whenever possible .

When combined with the use of "N" in city driving on streets where no extra speed is needed & while coming up to a stop and while at a stop , looking far ahead giving the needed room between cars in front of you to avoiding complete stops as much as conditions will allow with no jack rabbit starts during the tank I've documented as much as a 7-10 mpg improvement . One hard start is all can take to do away with the gas/fuel savings .

In fact I just documented over a several tanks in a Corolla an improvement from ~28-30 to 37+ mpg city by using these techniques . I took a 05 Accord from 24-25 to almost 30 mpgs on city only loops .

These numbers are while driving around the Denver metro area in traffic and from filling to the brim of the filler neck each time which is the only way to be sure you get accurate fill data to calculate consumption . NOTE , if the car is going to not be driven at least 10-15 miles right after the fill it should not be over filled like this !!!!! Filling up to top of the filler neck then parking can do damage to vapor recovery system in a gasoline car .

If these techniques are used properly you will achieve higher mpgs on city loops than on higher speed highway only loops . I have over 30 years of documentation to back this fact up ....
 

buck74

Member
Joined
Oct 9, 2010
Location
Wisconsin
TDI
2006 Jetta, 1.9L
Just bought my first Jetta TDI, 2006, 6A. I drive a lot on the freeway, 75 on the speedometer. First tank doing nothing more than useing the cruise control, and some coasting, 45mpg.

I was thinking of ording a K&N air filter, but it was stated early on in this thread that a stock filter would be better than K&N, does everyone agree with this?

I was thinking about a fuel and oil additive, what would people recommend? I already use BP fuel, and a full synthetic oil.

Thank you for any replies! Buck
 
Last edited:

oldpoopie

Vendor
Joined
May 14, 2001
Location
Portland Oregon
TDI
2001 golf gl, 2006 jetta, 1981 ALH swapped rabbit pickup, 1998 beetle
K&N can not even come close to the quality and performance of the OEM filtration. If you want good fuel economy, do the following.

Clean the intake manifold

buy good fuel

Tune the engine. The tuner will alter the maps for better economy and power. Emissions will go up, but....

Get good tires.....

Accelerate as little as possible

Slow down as little as possible

As for additives, I'd use a ZDDP in your PD's Oil for cam protection.
Fuel additives, I'd say anything is better than nothing. I use whatever is convenient.
 

ruking

Top Post Dawg
Joined
Mar 27, 2003
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
Just bought my first Jetta TDI, 2006, 6A. I drive a lot on the freeway, 75 on the speedometer. First tank doing nothing more than useing the cruise control, and some coasting, 45mpg.

I was thinking of ording a K&N air filter, but it was stated early on in this thread that a stock filter would be better than K&N, does everyone agree with this?

I was thinking about a fuel and oil additive, what would people recommend? I already use BP fuel, and a full synthetic oil.

Thank you for any replies! Buck
Whether we agree about K& N filters in TDI's or NOT, the answer is still; do NOT use a K & N filter.

I actually use 2,

1. Power Serve (Diesel KLEEN) aka grey bottles 400:1 dilution rate (@Walmart 80 oz @ 17 per 80 oz treats 250 gal). When low saps is NOT a requirement I have been having great luck and results with

2. Primrose 405 C 3000:1 dllution rate 1 qt (32 oz@ 11.87 per qt, 1 qt treats 750 gals) . Cost of Diesel KLEEN is 62% to 76.5 more per mile driven (lower % includes shipping cost).
 
Last edited:

jpv

Member
Joined
Sep 12, 2010
Location
alberta canada
TDI
2005 passat gls wagon
The turbo charger will suck all of the oil out of a K&N air filter and destroy your engine. Its fine with a normally asperated engine but the turbo sucks so hard that it will suck al the oil and crap that the oil has trapped in the filter......DONT DO IT !!!!
 

40X40

Experienced
Joined
Feb 12, 2006
Location
Kansas City area, MO
TDI
2013 Passat SEL Premium
The turbo charger will suck all of the oil out of a K&N air filter and destroy your engine. Its fine with a normally asperated engine but the turbo sucks so hard that it will suck al the oil and crap that the oil has trapped in the filter......DONT DO IT !!!!

Say WHAT?:mad:

Make up something else.


Do not use a KandN filter on a TDI, but the fact that the TDI has a turbo has absolutely nothing to do with why you should not use one on a TDI.

Bill
 

Tom Servo

Veteran Member
Joined
Jul 9, 2000
Location
LA (Lower Alabama)
TDI
2005 Gol TDI, blue and falling apart
Fuel additives, I'd say anything is better than nothing. I use whatever is convenient.
Alternatively, try to fill up with B2-B5-B20 biodiesel. I go through much less additive now that I have two different sources claiming B5 or better at the pumps. Anytime it's run, the engine sounds quieter, runs smoother and smokes less. I can only assume it's doing more good than harm. :cool:
 
Top