Gas mileage

I have searched and read many posts about gas mileage for the b5.5 Passat TDI and see varying ranges of mpg. I have logged mine by logging trip miles and dividing it by gallons pumped and I constantly get just over 32 mpg. Does this sound right?

I don't do much stop and go driving. I don't drive it like it is stolen. I do typically drive 80 mph on the highway and it reads about 2500 rpm at that speed. It is an automatic and has not been recoded, tuned or modified. I understand that the manual trannies will probably get better mpg but I have also seen many post of 40mpg for automatics. Are they hyper-mileing or letting the computer calculate the mpg? Should I be getting better mpg? Thanks in advance for your assistance.

80mph in an automatic, sure, low 30s is reasonable. I got 50mpg once when I was automatic, and I was coasting like crazy in the mountains. Otherwise I got high 30s moving at 75mph.

Try fuel mileage, Diesels' don't much like gas.

When I had an automatic, I could get 40+ mpg all day long on the interstates at 70 mph with the cruise on. 80 mph will definitely lower your mpg. How are you measuring a full tank? Are you filling it right up to the mouth of the filler tube or stopping when the pump clicks off? If the latter, do a search on "ventectomy."

50harleyrider said:

Try fuel mileage, Diesels' don't much like gas.

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50harleyrider, great catch! My lazy writing and proof reading shined through on that one.

owr084 said:

When I had an automatic, I could get 40+ mpg all day long on the interstates at 70 mph with the cruise on. 80 mph will definitely lower your mpg. How are you measuring a full tank? Are you filling it right up to the mouth of the filler tube or stopping when the pump clicks off? If the latter, do a search on "ventectomy."

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Owr084, thank you. I stop fueling when the pump clicks off. I searched for ventectomy and read several threads. Please correct me if I get this wrong. Ventectomy allows you to put more fuel in the tank and somewhat reduces foaming. This will allow more miles per tank but does not change mpg. Since I measure from pump click off, is that an inaccurate measurement for calculating mpg?

The auto shutoff function is not an accurate way to determine how much fuel you put back into the tank. It will vary between fill ups at the same pump and between pumps,

A ventectomy allows you to put around two gallons more into the tank.

Just a thought, you might want to check your thermostat. My mileage sucked because it was stuck open. The easy way to check it is to use a scan device hooked into the OBD port to read the real temperature. The temp gauge on the dash is barely better than an idiot light. Also, have you had a t belt change done lately? If so, the torsion values could be off. You need a VCDS cable to check that.

I just bought mine and after 3 tankfulls am averaging 6.4l/100Km or about 36MpG (US). I drive at (GPS Speed) 109Km/H or just under 2.2K RpM.

myrick72 said:

I constantly get just over 32 mpg. Does this sound right?
I don't do much stop and go driving. I don't drive it like it is stolen. I do typically drive 80 mph on the highway and it reads about 2500 rpm at that speed. .

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It might be OK. I don't constantly track my mileage on my wagon, but in the past I've gotten 32 mpg in mixed driving. Highway driving is has been 37-38 and I typically drive 70-75 mph.

One thing to remember is we both have a wagon. Wagons typically don't get the fuel mileage that sedans do. I probably gotten over 40 mpg only a few times though out my 162k mile ownership of my wagon. And that was when I had the factory Continental 16 inch tires. But when Changed out to Michelin Primacy tires, I found I had a 2-3 mpg hit.

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I got 42.7 MPG (hand calculated) on my way up to TDIFest lat month. 90% interstate, cruise control set at the speed limit. Car has a ventectomy, so I know that it was accurate.

36-37 bone stock sedan

Ive noticed that the TDI's "sweet spot" for MPG tends to be between 55-68. At least on mine. If I go 75 im usually getting around 35-40. When Im going longer distances in no particular hurry, I stay in the slow lane at 65-68 (The speed limit being 65-70 in my freeway stretch of I-15) When im in flat areas I use cruise control, and when im going downhill I just coast in drive. My goal is to get 800 miles out of my tank at least once, but when I mix my city driving into it, my max is about 650. Anyway, I have averaged 57mpg in a 70 mile drive before.
If you are on a 55 road, you can get 60+ easy, but there dosnt seem to be many long stretches of those roads anymore.

That's odd as I've been driving my 5sp manual converted Tdi Passat for about one year now and the best I've gotten is about 900 kms . I seem to be averaging about 7L/100km which would translate to 32 mpg. Not especially good as I was expecting at least 40mpg (US gal).
The other discrepancy I have is that at 2500rpm my speedo is showing closer to 70mph whereas others think I should be doing closer to 80 mph.
So I don't know what to think.

hughc said:

That's odd as I've been driving my 5sp manual converted Tdi Passat for about one year now and the best I've gotten is about 900 miles . I seem to be averaging about 7L/100km which would translate to 32 mpg. Not especially good as I was expecting at least 40mpg (US gal).
The other discrepancy I have is that at 2500rpm my speedo is showing closer to 70mph whereas others think I should be doing closer to 80 mph.
So I don't know what to think.

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You are sure you are measuring miles correctly? It looks to me like your odometer may not be accurate.

hughc said:

That's odd as I've been driving my 5sp manual converted Tdi Passat

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which transmission was put in your car?

Just got back from 1700 mile road trip. Averaged 33ish mpg. Cruised at 80-82 gps speed. (85 cluster). Also running big heavy 18" wheels and still have my auto in there.

UFO said:

You are sure you are measuring miles correctly? It looks to me like your odometer may not be accurate.

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Sorry, I should have indicated 900 km per tank and not 900 mi.

Zambee500 said:

which transmission was put in your car?

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According to my mechanics notes my transmission is a EEN 18122

QuickTD said:

I consistently get 5.8l/100km 40mpg (US) with that same gearing. It is a homebrew transaxle (V6 box with a EEN 5th gear). My commute is secondary roads, 100km/h and short, only 10km. Always get over 1000km to the tank. I would investigate torsion value on your car. Slight differences in cam timing can have a substantial effect on economy on a PD.

Oddly enough, I have a wagon with much taller gearing (DUK) and it gets considerably worse mileage (36mpg US) on a similar commute.

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Thank you QuickTD. Torsion value is something my mechanic wants to check as time allows and I'm sure he'll get around to it.
Presently he is hoping to make time to remove my gearbox as I need to replace the clutch and flywheel.

I do believe my f/e would improve if I could keep my speed at the 100kph, but that makes for pretty boring highway travel.

owr084 said:

The auto shutoff function is not an accurate way to determine how much fuel you put back into the tank. It will vary between fill ups at the same pump and between pumps,
A ventectomy allows you to put around two gallons more into the tank.
Just a thought, you might want to check your thermostat. My mileage sucked because it was stuck open. The easy way to check it is to use a scan device hooked into the OBD port to read the real temperature. The temp gauge on the dash is barely better than an idiot light. Also, have you had a t belt change done lately? If so, the torsion values could be off. You need a VCDS cable to check that.

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Thanks everyone for all the advise. During this year I had my thermostat and temp sensor replaced, so I hope that they are still good but I will check. The t-belt was changed a while back so I will have to get the torsion values checked out. Would there be any visible or audible symptoms of a slightly off torsion value other than fuel efficiency?

Nash_TDI said:

Just got back from 1700 mile road trip. Averaged 33ish mpg. Cruised at 80-82 gps speed. (85 cluster). Also running big heavy 18" wheels and still have my auto in there.

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That's about the average of Fuelly for the B5.5 station wagons (there are a few manual transmissions there but not enough to impact too much this average).

Please pay more attention to the averages in Fuelly or other databases with millions of miles recorded. Pay less attention to individual TDI MPG in this site (in my humble view).

tikal said:

That's about the average of Fuelly for the B5.5 station wagons (there are a few manual transmissions there but not enough to impact too much this average).
Please pay more attention to the averages in Fuelly or other databases with millions of miles recorded. Pay less attention to individual TDI MPG in this site (in my humble view).

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Thank you for the site. I had not heard of it. Are there any other sites that are highly used by the TDI community. I ask because there were only 6 2005 TDI Passat wagons and 2 2004s on the site. They averaged about 35 mpg which sounds about right. Everyone that I have talked has said I should be averaging around 36 mpg.

myrick72, you are welcome. Last time I ran the numbers on Fuelly for a B5.5 wagon automatic, the average came to around 33 MPG.

I think fueleconomy.gov allows people to enter their own observed mileages but the overall miles recorded are much less than Fuelly. for a given vehicle.