Low MPG???

[Pelican18TQA4]

Ok, I've just finished off my first full tank (it's the second tank actually, but the first one I forgot to track) and I'm rather disappointed in my MPG, 31 MPG!! Granted, that's almost double what I was getting in my previous car, but I expected something closer to the city EPA rating of 36 MPG. Granted, I suppose you could say I have a lead foot, but still, is this something I should be concerned about?

 

[whitedog]

We really need that sticky about how it's not very important to watch fuel mileage while breaking in the engine. Please read some other posts regarding poor mileage in new cars.

 

[SilverTDIPDJetta]

Ok, I've just finished off my first full tank (it's the second tank actually, but the first one I forgot to track) and I'm rather disappointed in my MPG, 31 MPG!! Granted, that's almost double what I was getting in my previous car, but I expected something closer to the city EPA rating of 36 MPG. Granted, I suppose you could say I have a lead foot, but still, is this something I should be concerned about?

I have an '04 Jetta Tiptronic. I know the transmissions are as different as night and day. Yours has an EPA city rating of 36MPG, mine is 33MPG. My lifetime average with 18K+ mikes is 30.1 now. When I first got it, I was only getting 28 - 30MPG. Recently, I have been getting 34-35 on the same commute and driving style, which is to say I baby it only until it is warmed up, then I drive it pretty hard. You will probably pick up at least 5MPG, possibly more as the engine gets broken in.

Mike

 

[yamsTDi]

I wouldnt worry about it right now. It takes 5k-10k miles until the engine will start reaching its peak mpg. My first tank was something like 32 or 33mpg. I now regularly get 42-46 mpg......give it some time, itll pick up!

 

[Dick_Larimore]

I picked up an '05 Beetle TDI with DSG on Friday so it's too early to tell how the mileage will be. However, I certainly expect better than 31 and will be disappointed if the mileage is that low. My two '05 Passats are getting 34 to 35 MPG right now (low miles and winter diesel fuel). These cars with a traditional auto transmission should get lower MPG than a Beetle DSG. I know there is a lot of talk that mileage will improve with greater miles on the vehicle. This is my forth VW diesel (and the forth PD) and I really have not seen mileage grow that much with time. The conversion to summer diesel fuel will positively impact mileage along with the benefits of higher temperatures.

All I can suggest is that you check the tire pressures (I am running 37 psi front / 39 psi rear) on Continental tires. Check for brake drag (unusually warm/hot wheels after a run), change the source of diesel fuel, and add a cetane booster (I use Power Service). If you have a roof rack on top of the car, expect a significant mileage hit.

 

[Thunderstruck]

Low tire pressure will kill you. I run 44/46 on mine. I took the car in last year for the first oil change, and told the dealer to leave the tire pressure alone, I'd handle it myself. On the next fill up my economy had dropped by 3 MPG. Checked tires the next day (had to let them cool off) and sure enough they had dropped pressure. High pressure really does not make the ride that much worse either.

 

[Pelican18TQA4]

I guess the problem really is is that I'm doing everything BUT driving the car to achieve the best MPG. Not that it's pedal to the metal all the time, but I certainly don't drive it as if my goal was to achieve the best fuel economy. As I mentioned, I'm pretty darn happy with achieve something in the 30s in city driving, but I was just concerned that it's not even what the EPA city rating is.

 

[whitedog]

I was just concerned that it's not even what the EPA city rating is.

It is the opinion of many here that the EPA numbers are as relevant to the real world as the internet is to the real world. In other words, the EPA numbers don't mean diddly-doo-doo, due to the way they get their numbers.

I'm not an expert on this, I only play one on the internet, but please be cautious believing those numbers and be patient with breaking in the engine.

 

[Pelican18TQA4]

Normally I could give a darn about the EPA #'s, but from what I've read here on tdiclub.com, it seems that most people achieve better fuel economy than the EPA #'s. That's the only reason I was asking. I didn't buy the TDI for better MPG, I bought it because I like the behavior of the TDI and the vehicle was available with all the options that I wanted.

 

[cp]

Lower-than-normal mileage and what can cause it:

Driving technique
Obviously someone who extracts the maximum amount of power out of the engine then throws it away by using the brakes heavily will do worse than someone who doesn't. My guess is this could be about a 10% penalty in a diesel. If you drive 80mph, don't expect to get the same mileage as someone driving 40. The math says that wherase you are covering ground twice as fast, you will be using eight times as much power to overcome aerodynamic drag in doing so. That power comes from burning fuel. You can easily lose 15-20% (maybe more) here.

Unusually high rolling resistance
Dragging brakes, bad wheel bearings, unusually high drive line losses, underinflated tires, goofy aerodynamic appendages all eat away at mileage.

Fuel injection problems
This is much simpler than a gas engine which needs a specific f/a ratio to work. The diesel isn't particular--80:1 is OK as is 35:1. The only thing it doesn't like is for the spray to be so concentrated that the fuel molecules can't find an air molecule to combine with. 'Slobbering' injectors waste fuel, accompanied by black smoke. A bad turbo or totally clogged air filter will waste fuel, too, but on the TDI I would suspect this wouldn't be a problem as the ECM should(?) restrict fuel to match air flow.

Fuel leaks
Needless to say, if the fuel you bought doesn't get to the engine, it can't contribute much to propelling you down the road.

Engine efficiency
Engines do gain in efficiency as the rings seat and internal resistance lowers, but usually not by huge amounts. Maybe 5%-10% to be gained after the engine is broken in. As engines reach the end of their useful life, they lose compression and efficiency drops, but not as much as one would think. Diesel usually get rebuilt because of excessive oil consumption, not excessive fuel consumption.

That's all I can think of right now. Anyone else?

So, if you pick from the list and find that you are someone who likes to race to stoplights and cruise on the highway at 85mph with a roof-top bike rack in a new TDI, should you expect to get 48mpg?

 

[whitedog]

Inconsistancies in filling If you aren't filling to the same point, or taking a total over a five tank range, your calculations will be off.

Failed math class If you don't do the math right even good numbers will end in bad results.

 

[Thunderstruck]

I'm up to 16.5K, and manage to meet the EPA estimates, although it's hard to know exactly how to define my driving since I do a mix of both. I don't baby the engine either, since short shifting to increase mileage can cause build up in the engine. I try to regularly go to 3K to shift, and run it to 4 at least once when running around.

 

[Magnulus]

I get better than the EPA numbers for a 2003 automatic. But then the EPA city driving might not be the same as what I'm driving (short trips through suburbia, usually light traffic). The usual tank of diesel gets about 36-40 miles per gallon. Worst tanks have been 34 miles per gallon.

Alot of people are getting great mileage, but then they are logging alot of highway miles. Just keep that in mind.

 

[uberdiesel]

Chin up. I just got 32 mpg on my very first fill up today. I'll chalk up my low start to: 1) a very young engine (500 +/- miles); 2) inconsistency in filling (I squeezed quite a bit of diesel in there after the 1st shut-off); and 3) speed (70-85 mph). I'll keep you posted, hoping yours (and mine) improve as the miles go by.

 

[TornadoRed]

I guess the problem really is is that I'm doing everything BUT driving the car to achieve the best MPG. Not that it's pedal to the metal all the time, but I certainly don't drive it as if my goal was to achieve the best fuel economy.

It sounds like you are driving the car properly, since your primary goal right now is to break in the engine. Better mileage will come, eventually. I saw litle improvement over the first 3k miles, then eventually about 5 mpg gain over the initial mileage numbers.

 

[McBrew]

I was getting average mileage (47MPG in a 2003 with 5-speed) until about 30k miles... then it slowly came up to about 50 MPG. My last three tanks have been between 49 and 51 MPG... and that's on winter fuel!

I'm not trying to brag about mileage... we all know that the older 90HP ALH engines got better mileage (but with less power). Also, I have the more thrifty 5-speed. Not to mention that the NB will take a hit due to increased drag. However, what I am trying to say is that break-in does improve things. At 5k, 10k, 20k miles, I was beginning to think this "break-in mileage" thing was a fairy tale. It just took a bit longer for my car... but it happened!

Oh, and I drive my car harder than I did at first. So the difference is really even greater. I'd say that it was an overall 5 MPG improvement, everything else being equal.

Try different brands of fuel, too. I have seen a difference in MPG related to fuel/additives. The supposedly good BP/Amoco fuel around here (Maryland) delivers relatively low MPG in my car (my brother noted the same thing in his TDI).

 

[burningmoney97]

Ok, I've just finished off my first full tank (it's the second tank actually, but the first one I forgot to track) and I'm rather disappointed in my MPG, 31 MPG!! Granted, that's almost double what I was getting in my previous car, but I expected something closer to the city EPA rating of 36 MPG. Granted, I suppose you could say I have a lead foot, but still, is this something I should be concerned about?

no - http://forums.tdiclub.com/showflat.php?C...true#Post947470

 

[Scirocco84]

Got 2 '03 Jetta's. One is racking up about 48MPG. The other is getting about 38MPG and when I first bought is the 0-10,000 miles I was getting about 48 with it also Highway. I believe something is wrong. if your getting under even 43. Anyone have any ideas what it may be? Replaced Mass Air flow, EGR and some of the vent hoses now and no change. VAG all checks out well with nothing showing. Arg!!