Terrible fuel economy alh autotragic

Alhjetta00

Member
Joined
Mar 8, 2021
Location
Bristol, Ct
TDI
2000 Jetta ALH 120k miles
My alh jetta with the notoriously terrible 01m auto has always gotten really poor fuel mileage. Last tank I averaged 24.8 mpgs (mostly city/some highway) which is pretty embarrassing. The tank has a "ventectomy" so I fill it all the way to the top every time and am pretty confident I am calculating fuel mileage correctly. It runs great. The egr was removed and cleaned thoroughly as well as the beginning of the intake(where I could reach with the egr removed). It was pretty clogged, so I wouldnt be surprised if the intake manifold is clogged further down. I kept the egr off for a year in favor of a "race pipe" hoping to clear out the intake but saw no improvement in fuel economy or power. The brakes aren't sticking, I checked and adjusted timing with vcds (was advanced off the chart, now is dead-on), and replaced the injector nozzles. The new injector nozzles are way better than the stock ones, but my fuel mileage has remained the same. I don't expect to get 50 mpg with the automatic obviously but 24 is a little ridiculous. Eventually when I get my hands on a good donor car I'll swap the tranny. Any input would be appreciated, thanks.
 

wildn

Well-known member
Joined
Oct 19, 2019
Location
Ventura,CA
TDI
2002 Jetta TDI wagon 5spd! 2011 Jetta JSW TDI DSG
I'm getting like 30-35mpg at the best. Is the injection quantity set within spec? what PSI are your tires at?
Mine has the 01m too and got like 29mpg but that was because I have a roof rack and the injection pump was leaking from all the seals. But I'm no expert.
 

Alhjetta00

Member
Joined
Mar 8, 2021
Location
Bristol, Ct
TDI
2000 Jetta ALH 120k miles
Last I checked my injection quantity at idle with a warm engine was around 6.4 mg/str. My tires are aired up to 36 psi. I was thinking...my car is missing all the engine plastics at the bottom and sides and whatnot. I'm sure that doesn't help with mpgs with all that air resistance. When the wind blows while on the highway it literally moves the car and I have to counter steer a bit. I'll buy a set of plastics and a metal belly pan and see if that does anything. My injection pump is pretty noisy but I dont think it's leaking anywhere. I'm hoping when I do the manual swap the mileage will go up.
 

hskrdu

Top Post Dawg
Joined
Oct 17, 2003
Location
Maryland and New England
TDI
2003 Golf GLS 4D 5M, 2015 GSW SE 6M
I see you said "always" in your description. Do you have good long term data to compare to current, so that you can eliminate variables and see changes? Winter fuel and cold temps in CT will ensure that your lowest FE will be Jan-March. City driving will obviously hurt a lot, too. Can you take it on a highway run up 84 and 91 at 65mph on a free day to see how much fuel you use over the first 400 miles (highway only)?
 

Alhjetta00

Member
Joined
Mar 8, 2021
Location
Bristol, Ct
TDI
2000 Jetta ALH 120k miles
I see you said "always" in your description. Do you have good long term data to compare to current, so that you can eliminate variables and see changes? Winter fuel and cold temps in CT will ensure that your lowest FE will be Jan-March. City driving will obviously hurt a lot, too. Can you take it on a highway run up 84 and 91 at 65mph on a free day to see how much fuel you use over the first 400 miles (highway only)?
So I don't have anything written down or logged unfortunately. Everytime I fill up I check and I've done that since I got the car. The highest I ever remember seeing was 35 mpg and that was all highway to westerly RI and back. I do mostly city driving and every fill up is below 30 mpg. Like I said, the latest was 24.8 mpg, which is the worst I've seen. The snowscreen was pretty clogged and I cleaned it and replaced the air filter before the last fillup so I kind of expected there to be an increase, not a decrease. As for the temperature..in the summer I see 28-29 mpg and in the winter I see 26-27. I'll start logging the data so I can eliminate variables. I take it for a long ride this weekend to see how it does.
 

hskrdu

Top Post Dawg
Joined
Oct 17, 2003
Location
Maryland and New England
TDI
2003 Golf GLS 4D 5M, 2015 GSW SE 6M
It's hard to really troubleshoot and identify specific causes (and not throw parts at it) without tracking FE and conditions, but it sounds like you have a decent grip on the numbers. My suggestions are to first start tracking data, and then start troubleshooting. An all-highway trip on a warm engine will give you some winter-fuel data for immediate comparison. You could go from Bristol up to Montpelier for lunch at Skinny Pancake- fill up after the engine is warm, maybe near the airport, and fill up when you get back for immediate numbers.

Otherwise, I'd work through OH's tips for improving fuel economy to cover the common items you haven't hit yet. For me, I'd definitely clean the intake, new CTS, check the thermostat operation, and hit all the little things. FE is really all about adding up the little things, but if there's a baseline problem, the little things are hard to see.

What size nozzles did you put in? Were they tested and balanced and all that jazz? Is the turbo providing boost when requested? 01M serviced and trans oil good? All filters good? Engine warms up at the correct rate?

The underbody plastics help a bit for FE, but mostly on the highway. For city, I've found much improvement can be had through driving style- but there are obvious limitations. Heavy wheels are a burden in the city, along with worn suspension. LRR tires at higher PSI help, but may not feel great over the bumps.

What are you distances? If short trips, obviously your running winterized fuel on a cold engine, which is another reason why city numbers can be low.

The thread I referenced:

 

Alhjetta00

Member
Joined
Mar 8, 2021
Location
Bristol, Ct
TDI
2000 Jetta ALH 120k miles
Over the summer the thermostat went out and was stuck open. I replaced it, along with the CTS, and now it warms up pretty quick. The nozzles were replaced with Bosio sprint 520 .205 (the stock nozzle for the European 110hp tdis). I didn't balance them or do any tuning, but the injector balance according to VCDS is in spec. It runs just as smooth as it did before with slightly more "pep." The FE didn't change at all when I replaced them which suprised me. Turbo builds boost fine (spikes around 15 psi...holds 13 for a while). The tranny was serviced before I bought the car around 90k miles (now has 115k). I replaced the fuel filter maybe 5k miles ago, the air filter 400 miles ago, new wheels & tires this summer as well as an alignment and all that. I only really drive maybe 30 min trips at a time and its all city. Like I said maybe this weekend I'll head up north and get some baseline numbers down so I can compare when I clean the intake. I'll probably just buy a new intake because cleaning the soot and oil mixture from the egr sucked and they arent really all that expensive. Thanks for the help.
 

hskrdu

Top Post Dawg
Joined
Oct 17, 2003
Location
Maryland and New England
TDI
2003 Golf GLS 4D 5M, 2015 GSW SE 6M
It sound like you have a good grip on things, and have been knocking out items on the list, which puts you ahead of 90% of people who are troubleshooting low FE. I'm not certain that VCDS will reveal what you need to know about the nozzles, but I have zero expertise there. Are the wheels still 15"? The OE Avus 15" wheel from VW is a favorite for fuel economy, especially in the city, because they are so light. Any chance that you have to lower the mass at each corner which drags down FE in city driving will help. Your overall mileage is quite low, but you could always try running a can of Liqui Moly Diesel Purge through the injectors. It's only 8 bucks or so, and I used to do it after 50,000 miles or so and could usually graph a slight improvement. If you have any concerns about the fuel source, you could also add a couple of ounces of Power Service (white bottle) to the tank for a cetane boost. Just include it in your FE calculations for accuracy.

Intake: I would suggest to check with Mike McCann just north of you, he sometimes has an intake cleaned and ready for install. Not many people are allowed to touch my cars, but I go to Mike often (413 Auto).

If I had an 01M, and was driving in the cold, using winter fuel, doing short trips, and the engine was not spending much time at operating temperature (ignore the non-linear temp gauge), I would expect to get ~30mpg, so it sounds like there's definitely room for improvement.
 

Alhjetta00

Member
Joined
Mar 8, 2021
Location
Bristol, Ct
TDI
2000 Jetta ALH 120k miles
The wheels were originally the 15" avus but I bought a set of 18" aftermarket rims and tires. The old lady who owned the car before me apparently liked parking really close to the curbs so thats why I got new wheels. They are slightly lighter than the OE wheels (although rotational mass is probably the same if not more) but I didn't see any difference in FE after installing them this summer. I've talked with Mike about possibly doing a stage 1 or 1.5 malone tune a while back but he didn't seem to like the idea (it being an auto). I'll definitely try the diesel purge. I'd like to tune out the egr if possible after cleaning the intake to avoid having to revisit that problem again and again. I just spent a bunch of money and time on a new steering rack and tie rods chasing down a front end clunk to no avail. I'd like to replace the intake myself but I'll see if maybe I can work out a deal with Mike to possibly get me a clean one and I'll send him my old one..something along those lines.
 

251

TDI Owner/Operator
Joined
May 11, 2002
Location
NW IN
TDI
2015 Passat TDI SEL
The wheels were originally the 15" avus but I bought a set of 18" aftermarket rims and tires.
The city driving and the 18" wheels are a large portion of your poor fuel economy. A friend of mine's A4 Jetta that ran 17" wheels in summer saw an INCREASE in fuel economy when he went to 15" wheels in winter. Ditch the 18" wheels/tires for 15" or 16". I had 16" wheels on my ALH and and still got great fuel economy as the overall diameter is almost the same as OEM 15" wheels/tires.

Find a cheap set of 15" in the salvage yard, Craigslist, VW Vortex or the classifieds here to minimize your cash outlay. Put 'em on and track your mpg's - I bet it will go up! Then you can get a nice set of 15" or 16" rims.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
My 2000 Beetle came with the O1M autotragic. Summer, winter - usually 35-38 MPG. Stock 16 inch wheels. Having a 5 speed manual swap did wonders for MPG - immediate jump to 45 MPG (still is my roadtrip MPG), and mostly town in KC is about 42 MPG.
 

hskrdu

Top Post Dawg
Joined
Oct 17, 2003
Location
Maryland and New England
TDI
2003 Golf GLS 4D 5M, 2015 GSW SE 6M
In the interest of fuel economy, I would 100% suggest changing the 18in wheels for light 15in wheels. The variables associated with wheels, tires, and fuel economy are complex, and not neatly compartmentalized, but (especially for city driving) weight and increased rolling resistance will lower FE. I know you said above that (1) You saw no change when you swapped from 15in Avus to 18in aftermarket, and (2) The 18in aftermarket wheels were slightly lighter than the Avus. If you weighed the aftermarket 18's, and you know for certain they are lighter than the OE 15in Avus, then I'll say no more. However, from memory, the Avus weigh just over 16.5 pounds, and that's hard to beat in an 18in wheel. Next you have tire weight and if you look at three common LRR tires from Michelin, Conti, and General in 195/65/15, they average about 18 pounds. The exact same tire in several widths and sidewall heights near 225/40/18 have an average weight of 22 pounds. That's a notable difference. Next is rolling resistance- Although the relationship between tire width and Crr is not as clear as some assume, the tires fitted to a MkIV 18in wheel will almost always have greater Crr than the 15in counterparts sized to MkIV wheels. In addition, although you can find 18in tires marketed as LRR, I will anecdotally suggest that the most fuel efficient tires for most manufacturers are found in narrower, taller tires. The end result of these factors is that you likely have heavier tires, possibly on heavier wheels, with greater rolling resistance- all of which lowers FE, especially in the city. Owners who travel on the highway can often offset these factors because highway travel changes parts of the equation.

That brings us back to number (1) above, in that you didn't see a MPG hit when going from 15's to 18's. FE gains and losses are difficult to track, even when your fueling and measurement practices are fairly standardized. Single tank samples are only indicative of the conditions for that tank, and so long term accurate records are a must. Often, owners will make a change and watch the fuel gauge for a while and report they didn't see a difference, but small changes are hidden by other factors. In your case, where we suspect there is something larger going on, the loss of FE at the corners may be hidden by the low baseline established by the engine itself, so you aren't seeing the hit. Bottom line, 99.9% of all owners who go from am 18in combo to a 15in combo will be enabling better FE- whether they see the results or not depends on many things.

Also, unless you've made VCDS adjustments, your ODO with 18in wheels will under-report miles, so that helps a little in calculating FE, but not much. And I remember a thread where someone suggested Enkei wheels for their low weight. I looked up their RPF1 18in wheel and it weighs 18.3lbs, so you may be adding even more than just tire weight at each corner.
 

Alhjetta00

Member
Joined
Mar 8, 2021
Location
Bristol, Ct
TDI
2000 Jetta ALH 120k miles
Update: I did the manual swap, malone stage 3 tune and added underbody plastics. My mpg now while also "enjoying the tune" is 40, which is fine by me. It's amazing how much of a difference the manual makes for fuel economy. I'm sure with a lighter right foot I could bring that up to 45-50.

Thanks again for the help!
 

Tom in PT

Veteran Member
Joined
Jun 7, 2017
Location
Twilight Zone, WA State
TDI
2005 Passat sedan - SOLD; 2013 Passat DSG; both purchased new
My '013 with DSG gets better mpgs than my old 2002 Jetta wagon with a manual, even more so before the '013 was fixed after dieselgate.

My 013 also gets at least 6-8 mpgs better than my 05 Passat with 5 speed tiptronic. I am not sure why that is, could be aerodynamics and not transmission.

Are the drag coefficients for VW cars posted anywhere?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
A healthy, stock, well maintained ALH+01M can easily achieve its original EPA estimated numbers, usually in the 30-45 range. Obviously "city" is a much more flexible and broad term, and "highway" is almost always going to be limited to around 60 to 65 MPH.

The 01M shouldn't be doing anything off that would hinder fuel economy like slipping or not locking up when it should without setting a DTC and turning on the friendly MIL. Sure, it's a lousy transmission, but when it is working correctly, it does its job.

25 MPG in all city driving is probably not *that* far off, depending on how you drive. You think that's bad, the 2.slo+01M will struggle to hit 20 under the same conditions. Changing the DSP to Economy mode may help a little, although I prefer the Sport setting with the diesels.... 90hp needs all the help it can get.
 

Bengoshi2000

Veteran Member
Joined
Jun 24, 2013
Location
Triad NC, USA
TDI
2002 Golf (0M1)
The biggest change that brought my FE back up on my ALH+01M came after replacing a leaking vac pump/hose/brake booster. All seemed to fail about the same time. I also replaced all vac lines. In 50/50 hwy/city driving I'm back up to the upper 30's. All city driving now yields lower 30's. Prior to, I was getting low/mid 20's.
 
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