What is venting and why does my car not get the mileage i see others achieving?

Joined
Aug 29, 2020
Location
United States
TDI
2002 1.9L Jetta TDI
I've owned my 02 tdi for close to a year now and I'm discovering that my average of 40-45 mpg is, in fact, quite measily. In my searching through the forum i came across several different people mentioning venting. What is this? Also is there some kind of additive that can help increase by mileage? I had one random tank of fuel that got me 50mpg (638 miles) on the dot but since then have never repeated that. Egr is deleted and has an aftermarket turbo which is still the oem size.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
The mods to get into the 55 mark is imo not worth it u less fuel is $5 a gallon or you out 100k a year in it.
You can brush close to 50mpg if you learn how to hyper milage drive your car. Getting a scangaugeII will make a big difference in you learning how to maximize your milage
 

STDOUBT

Veteran Member
Joined
Jul 30, 2007
Location
Portland, effing Oregon
TDI
dos jettas
I've owned my 02 tdi for close to a year now and I'm discovering that my average of 40-45 mpg is, in fact, quite measily.
Not sure who told you that, but they're wrong.
From the manufacturer:
City: 21 - 42 mpg · Highway: 29 - 50 mpg
There are several things you can do to increase fuel efficiency. Additives are not among them.
Just make sure you use 100% synthetic motor oil.
https://forums.tdiclub.com/index.php?threads/tips-for-fuel-economy.342274/
 

Gothmolly

Veteran Member
Joined
Feb 3, 2005
Location
Providence, RI
TDI
2002 Golf
Ive had this car for 15 years, lifetime average around 46 mpg, best mileage was a 52 mpg tank of pure highway.
You're in good shape. Check tire pressure. Automatics can also suffer a mileage hit.
 
Joined
Aug 29, 2020
Location
United States
TDI
2002 1.9L Jetta TDI
Appreciate all the replies! I was just looking around different places on the forum seeing people posting numbers into the 55-60 and some even higher and assumed i was doing something wrong.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
Wants good milage
Spends savings on pointless street cred

If you insist on wheels
Get a proper set of era correct BBS wheels
The ones you linked wont even survive a speed bump!
 
Joined
Aug 29, 2020
Location
United States
TDI
2002 1.9L Jetta TDI
Well i guess it's a good thing we don't have speed bumps! Also if i wanted "era correct" then i would've posted those. I simply want opinions on which color is nicer.
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
The high numbers you see posted here are usually the outliers or sometimes just the outright liars, not the normal. Few people are willing to drive and/or spend the money to get that kind of extra mileage. A lot of things go into great fuel economy but the biggest is how you drive not what you can buy.
 

jokila

Vendor
Joined
Dec 3, 2004
Location
Houston, Texas
TDI
2003 Jetta GLS, Manual
Venting really has nothing to do with MPG. About the only way it can relate to MPG is making it possible to be consistent when filling the tank.

It does help your total miles to a tank, obviously.
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
Where are you located? And what type of driving do you do: city/suburban/highway? I can tell you that 18" wheels and tires will negatively affect FE. The Avus 1s that STDOUBT posted are a good option. I currently have those on both of my MKIVs.

Regarding FE, lately I've been getting really good FE in my '02 Wagon, but I'm not sure why. I have a number of mods, but they weren't driven by FE, but to increase power. Regardless, I'm getting right around 50 MPG on most tanks. My last fill was 51.3, and that included a one-day trip to Washington DC and back, and I drove at 80+ MPH for most of the trip. Mystifies me as to why the FE is up there, but it is.
 

jayb79

Veteran Member
Joined
May 20, 2000
Location
Exeter,NH
I can easily get 50plus MPG in the summer when I am below that it is because of 80plus mph highway runs (resulting in hi 40s mpg). I run my stock size tires and wheels at 40-42psi and 99.9% of the time my car only has me my laptop and a smallish tool bag in it. Big and or heavy tire and wheel setups have been by far my worst mpg hitters. My snow tires have been larger diameter than stock for more ground clearance and this causes an mpg hit as well, (remember to calculate in the new odometer numbers if the tires are larger).
 
Joined
Aug 29, 2020
Location
United States
TDI
2002 1.9L Jetta TDI
I can easily get 50plus MPG in the summer when I am below that it is because of 80plus mph highway runs (resulting in hi 40s mpg). I run my stock size tires and wheels at 40-42psi and 99.9% of the time my car only has me my laptop and a smallish tool bag in it. Big and or heavy tire and wheel setups have been by far my worst mpg hitters. My snow tires have been larger diameter than stock for more ground clearance and this causes an mpg hit as well, (remember to calculate in the new odometer numbers if the tires are larger).
Well it seems that i could definitely increase my tire pressure, i believe im currently running them around 35, which should help a good bit as i already average 42-43mpg.

I guess i didn't really think about how much rims would affect my mpg but in my roughly 1 year experience in a tire shop, after market rims are generally a good bit lighter despite being bigger so who knows as far as that goes. Perhaps maybe some info on that, that I'll look into later.

I will only be running the new rims over summer months and the stock ones in the winter though which should help get me a decent idea on how that performs. And i believe the current tire and the tire i intend to put on them should maintain the correct speed but i will double check after installing.
 

USMCFieldMP

Veteran Member
Joined
Jun 30, 2011
Location
Fort Worth, TX
TDI
2014 Jetta TDI
I'm betting those JNC wheels are quite heavy; keep in mind that if you get wheels that are actually heavier than stock... you're going to lose MPG... and the car will be slower, handle worse, brake worse, etc.

A proper set of lightweight wheels will actually help your MPG. My go-to has been the RPF-1; you can get them from TireRack and are usually around the 15 lbs/ea mark. My factory MK4 Long Beach wheels were 23 lbs, iirc. 8 lbs per corner makes a difference - I ended up gaining about 4 MPG, but that was a 24v VR6, not a TDI. I try to run the smallest diameter that I can, because they're lighter that way. You can do the same with 2-piece rotors to shed more rotational/unsprung mass.

Of course, you'll never offset the cost of these items with fuel savings ?, but they can certainly make the car a lot more lively and fun to drive.

It's your car; do what you want.
 

Mongler98

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Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
1st Please stop calling them rims. they are wheels, not rims.

2nd Fuel econ goes hand in hand with performance. better spray patterns from upgraded nozzles, better boost maps from better more modern turbos, cooler air charge from bigger FMIC, better airflow on a better intake manifold, so on and so forth. if you do not increase the fuel use, but increase how it burns, you get more power and more MPG. Whenever you do a power mod, you end up getting a jump in MPG as long as your not going full at it. Of Course a tune is the best way to maximize this with supporting mods, but i was able to get 62mpg on average going cross country at 75mph cruise control with my 764's gt2052, and pd150 intake and a bunch of supporting mods on 205/40ZR-17 SUMITOMO HTR Z II 17x8 Axis OG Europa SDC with NO TUNE what so ever (other than the stock one) when i put the stage 6 tune in, the best i could do was about 40, but that was because race car and i didnt care, but i still was at like 230 HP at the wheels so.......................
Full list of mods and a video
still got a normal in town mix/highway mix of about 56 if i drove like a grandma, 8mpg track, about 48 the way i drove it lol
 
Last edited:

BigAndy

Veteran Member
Joined
Apr 19, 2002
Location
Northern BC
TDI
99 A3
Keep in mind there are a few Canadians and Europeans on this site and imperial gallons is the gallon used and that gallon is 4.54 litres vs 3.98 litres for your US gallon. So when a Canadian says they get 62mpg - its 62 miles on a slighter larger gallon...
 

jokila

Vendor
Joined
Dec 3, 2004
Location
Houston, Texas
TDI
2003 Jetta GLS, Manual
Keep in mind there are a few Canadians and Europeans on this site and imperial gallons is the gallon used and that gallon is 4.54 litres vs 3.98 litres for your US gallon. So when a Canadian says they get 62mpg - its 62 miles on a slighter larger gallon...
Yet they measure speed in kilometers per hour and purchase fuel in liters. Is that a mess or what?
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
Northern MD (HAGERBUSH)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress)
dont forget mericas butload measurment! A 'butt' is a traditional unit of volume used for wines and other alcoholic beverages. A butt is generally defined to be two hogsheads, but the size of hogsheads varies according to the contents. In the United States a hogshead is typically 63 gallons and a butt is 126 gallons.
 

USMCFieldMP

Veteran Member
Joined
Jun 30, 2011
Location
Fort Worth, TX
TDI
2014 Jetta TDI
dont forget mericas butload measurment! A 'butt' is a traditional unit of volume used for wines and other alcoholic beverages. A butt is generally defined to be two hogsheads, but the size of hogsheads varies according to the contents. In the United States a hogshead is typically 63 gallons and a butt is 126 gallons.
Hogshead, slug, blob, pound (mass) - not to be confused with pound (force)... there's 3 of these in one of those... 12 of this in one of that... and 4.5 of that in one of them.

All reasons that I grew to hate the US/Imperial system while going through engineering school. ?
 
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