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VW Passat TDI

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Comments

  • cosmocosmo Posts: 203
    If your figures are based on actual fuel added at fill ups, you are getting better fuel economy than I am with my '04 TDI wagon. If your figures are based on the trip computer readouts, you may be in for a let down when you refuel. My trip computer is consistently optimistic by 4 mpg.
  • cosmocosmo Posts: 203
    There is a discussion regarding this issue on another popular TDi forum. The subject to search for is "Shifting patterns of a automatic TDi". I have found that flooring the pedal gives me diminishing returns in regards to acceleration and a significant increase in exhaust smoke. I found a sweet spot that seems to give me the best acceleration with less smoke, and the shift point in automatic mode is 4,000 rpm. You have to experiment. It didn't take me long to get the feel for it. Off the line, depress the accelerator smoothly as if you were aggressively but sanely driving a manual transmission, i.e. not like you are a fifteen-and-a-half year old that pops the clutch and mashes the accelerator and either kills the engine or burns rubber. That sudden dumping induces Tip lag, and acceleration is temporarily zilch. To accelerate when already in motion, manually downshift one lower gear and go for the sweet spot. Flooring the acclerator will cause the Tiptronic to downshift too far and you lose the advantage of the TDI's torque.

    Works for me. I'd like to learn what works best for the rest.
  • eliaselias Posts: 1,828
    thanks cosmo. i'll try to incorporate your advice re acceleration and will report back if i notice anything that might interest you or others here. i actually wish the car would smoke *more* like my 2003 jetta TDI 5-speed would do - because i tend to enjoy putting a soot cloud on tailgators. in related news, i noticed that it seemed impossible to make the car smoke on the low-sulfur california diesel fuel. but on nevada fuel, ascending into some nevada/wyoming mountains around 7000 feet, i put a magnum opus sooty onto a left-lane hog who was dawdling up the mountain. i was lovin that, but i have it on good authority that such enjoyment makes me an idiot!

    i've looked at two other VW forums (fora?) and have not found the thread to which you refer but i'll look for some others. wink wink nudge nudge say no more. funny enough, on one of those other VW forums i found a discussion about the next-gen version of my other car, pontiac GTO. sometimes i've got the need for speed/acceleration, other times i've got the need for diesel mpg :)

    in diesel price news, it's nice to see the price of diesel *almost* as low as the price for regular unleaded here in new england and in some other states on I-80...
  • bzackbzack Posts: 12
    Thanks! My figure is indeed based on trip computer. Even though it may not be accurate I'm still surprise in a good way: compared to my Grand Cherokee, Passat is extremely fuel efficient.
  • I am new to the TDI, loving it after 5 days. My commute is mostly highway -- I have not needed to buy fuel yet, but the computer tells me I am getting about 41 mpg.

    1) I do notice it seems to be better if I keep my speed to 70 or lower, but I still can get 38 mpg at 75. Does that match your experience?

    2) Will my mileage improve after the engine is broken in?

    3) I "drive" it like I drive gasoline cars -- I turn the key, start and go. Of course, it's 100 degrees here in PA. Should I be waiting 5 seconds or watching some glow light?

    4) I got the GLS for $23,677 before tax and tags. How did I do? That was $1800 less than the first dealer I spoke to. Once I got below invoice, I stopped shopping. I also feared that the TDI supply would dry up.

    5) Can I play MP3 CDs in the Monsoon, or just conventional CDs?

    Thanks! I look forward to joining the legion of loyal VW drivers.
  • sebring95sebring95 Posts: 3,225
    2) Will my mileage improve after the engine is broken in?

    Historically, the TDI engines have been quite tight when new. Performance and economy goes up after 5k-15k miles.

    3) I "drive" it like I drive gasoline cars -- I turn the key, start and go. Of course, it's 100 degrees here in PA. Should I be waiting 5 seconds or watching some glow light?

    No need to wait in the summer, but when temps start dipping you might start making a habit of waiting. The glow-plug light should just blink right off if warming isn't needed. I have three diesel vehicles and pretty much catch my self waiting to start every vehicle I own :) I'm not sure how fast you throw it in gear after starting, but you really should wait maybe 5 seconds or so at the least. It's very hard on a transmission (any vehicle) to be thrown straight into gear before pressue is brought up. I usually start car, then put on seat-belt, etc. before going into gear. Just a little tid-bit.
  • smokerrsmokerr Posts: 5
    We have a 2005 Passat TDI wagon, automatic trany with 4,000 miles

    Fuel mileage on the highway has been 38mpg (trip meter reading, with 3 people, packed to the roof with baggage).

    Two people and some baggage, 40-42 (lower with headwinds, higher figure neutral). Actually measured, not trip meter readings.

    Trip meter is a .2 to .5 high on the highway, and 1.5 to 2 mpg high in town (assume the algorithm has a harder time calculating right with frequent speed changes).

    It should get better after full breakin, uncertain on the Passat with its special break in oil (imprvoed very fast intitialy), but typical 10-15k in a diesl will max out.

    Under 70 is best economy range, though I have had the higherest reading in town, very early moring, 35-40 mph speed limits and hit all the lights, computer reading of 43.5 mpg.

    Do not wait for light, as it does not acivagte at high temps. Read manul for low temp ops (40 degrees and below I believe).

    You can increase mielaege with some tricks, put in netural and coast to stops as far in advance as you can (it maintains speed very well on the level), coast down hills, turn engine off if waiting for more than 30 seconds at hte light (also in manual).
  • eliaselias Posts: 1,828
    putting the car in neutral & coasting is not a way to save fuel - to the contrary. it's a waste because it uses fuel. instead, if you keep the car in gear & downshift as you coast down to a lower speed, zero fuel is used. as far as i know, this is true for all current vehicles, both diesels and gassers and has been the case for all fuel injected cars for the past couple of decades.
  • joss1joss1 Posts: 2
    As fare as finding "Power Service Diesl Kleen" and other similar brands, go to a bonafide truck stop off a highway. They have a many different brands. Even ask a trucker what they use in thier rigs for some more feedback.

    John
  • Good stuff. I have only bought gas one time, and I hadn't set the trip odometer beforehand. So right now, all I have to go on is the onboard computer.

    Strictly on the turnpike at 60mph, I get 45 mpg readouts. On my whole commute this AM, including miles before and after the turnpike, it was 44 mpg. I never exceeded 60 and accelerated gently.

    At 70 mph, mileage drops to about 41. At 80 I can still get 38. This is no luggage and just me in the car.

    Regarding coasting: of course, the car consumes less gas idling in neutral than it does in gear. Before the Passat TDI, I drove a 5-speed and had downhill backroad spots in my commute where I would step on the clutch and coast for a half mile or more. But of course, taking your foot off the gas in an automatic (the only available trans for the Passat TDI) creates a drag. That is useful when approaching a stop, since it saves on brakes, but otherwise a waste of momentum. It is simple to shift into neutral and coast, but here is my question:

    Is it not hard on the auto transmission to pop in back into "D" when you are going about 40 mph? Might that shorten the life of the trans?

    And, in Tiptronic mode, is there any way to go from 1,2,3,4,5 into N? :confuse:
  • sebring95sebring95 Posts: 3,225
    Regarding coasting: of course, the car consumes less gas idling in neutral than it does in gear.

    Actually, that's not true. When you push in the clutch or coast in neutral, the engine burns fuel just as if it was idling in the driveway. When coasting in gear, the motor is actually turning with the transmission and not burning fuel. I was skeptical a few years ago when I first heard this, but confirmed with VAGCOM software hooked to my TDI. If I coasted in gear, the fuel injection drops to 0g/second. At about 10mph, there's not enough power available to maintain and the injection will kick back on. When idling or coasting in neutral, it runs at about .9g/sec. Turn the A/C on while idling and it consumers 1.2g/sec. (i believe those are the right numbers, it's been awhile.... :) )
  • Wow. I'm learning something.

    Now is this true just of the TDI? Or all cars?
  • One more question: Long ago, I heard that diesels use very little fuel at idle, much less than a gasoline engine.

    Izzat true?
  • sebring95sebring95 Posts: 3,225
    I used to think it was just the diesels that didn't burn fuel when coasting in gear, but it's been rumored the gassers do it as well. I can't confirm that though.

    If I ever come acrossed a gasser VW I can hook my VAGCOM to, I'll find out the difference in idling. Diesel doesn't use much fuel when idling, but I really don't know how to compare. Diesels are typically smaller displacement than similar powered gassers, so I would thing pound for pound they could burn less fuel. I dunno really though.
  • cosmocosmo Posts: 203
    Coasting with the clutch pushed down for a half mile is cruel and unusual punishment for a throw out bearing. Likewise, I've read several sources that advise against coasting in neutral with an automatic because it hinders lubrication within the transmission. I haven't free-wheeled since I traded my 1959 DKW 3=6 for a 1963-1/2 Falcon Sprint convertible. (Two cars I wish I still had.)
  • eliaselias Posts: 1,828
    t-pie, rent a clue here and learn from those more knowledgeable than yourself about the basics of modern fuel injected vehicles. your "regarding coasting of course" comment is flat out wrong.

    as for driving a 5-speed and stepping on the clutch & coasting, if anything that is more counterproductive and wasteful of fuel than doing it with an automatic/slushbox. for the passat tdi it's an smg transmission not a slushbox so you are doing essentially the same (wrong) thing.

    also your "but of course, taking your foot off gas" comment seems to be equally wrong. however your third item, a question about the auto trans, is a better one. so you don't get a "three-fer" of wrongness for your post ! go for it next time if you dare - what other wild & wacky driving techniques do you have.

    to answer your question: IF volksy programmed & designedtheir trans properly, it should be fine to go in and out of neutral at any speed. however that's a big IF - you may be aware of the BUCKING issue on these passat TDIs - they all do it - but the gassers do not - i consider it an indication of a design/programming flaw.

    as for the final question, a way to go from 1,2,3,4,5 to N, that's a good question, i have actually wanted to do that on rare occasion such as stopping in a parking lot. but not for the reasons you are doing it.

    happy & safe motoring to ya! if you are going to use driving techniques wasteful of fuel, at least you are doing it in a diesel and wasting that much less fuel ! you go!
  • Likewise, I've read several sources that advise against coasting in neutral with an automatic because it hinders lubrication within the transmission.

    How would that be different from idling in neutral at a stoplight? Either way, the engine is idling and the transmission disengaged.
  • Coasting with the clutch pushed down for a half mile is cruel and unusual punishment for a throw out bearing.

    Can you elaborate? The clutch is disengaged, hence no friction or wear on the clutch. What is the throw out bearing, and how would this driving style affect it? I drove my 5-Speed Legend 200,000 miles using that technique. And never once had the clutch serviced.

    Appreciate your insights.
  • t-pie, rent a clue here and learn from those more knowledgeable than yourself about the basics of modern fuel injected vehicles. your "regarding coasting of course" comment is flat out wrong.

    as for driving a 5-speed and stepping on the clutch & coasting, if anything that is more counterproductive and wasteful of fuel than doing it with an automatic/slushbox.

    also your "but of course, taking your foot off gas" comment seems to be equally wrong. however your third item, a question about the auto trans, is a better one. so you don't get a "three-fer" of wrongness for your post ! go for it next time if you dare - what other wild & wacky driving techniques do you have.


    I am happy to learn from others here. It's good stuff.

    Sebring made the case as to why a car coasting in gear uses less fuel than one out of gear.

    However, you have to judge the circumstance, no? If you are intending to slow down (for a light, toll booth, etc) then it makes sense to take full adavantage of engine braking while also saving fuel. But if your intention is to maintain momentum and let gravity work for you, coasting out of gear is going to cover more distance on less fuel than coasting in gear and suffering engine drag. Now, it still may be a bad habit in the Passat if there is some science to demonstrate that it is harmful to the car to go in and out of neutral while moving.
  • enzanbenzanb Posts: 1
    Have heard about the 7500 miles needed for registration clause, but suppose I buy the TDI out of state, with residency in that state of purchase and then move to California say within the first 2000 miles. Any help? Thanks.
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