Poor MPG, is there a concensus?

[johnboy00]

You should definitely try another station for a couple of tanks to confirm they are not cheating you out of fuel. I don't think fuel economy effects from fuel would be that large. One thing to consider is that you are driving a different route now.

Were you close to a highway exit before the move or father away now? Are there more traffic lights or more traffic? These effects can easily have a 10+ percent effect on your fuel economy.

 

[traubenberg]

Were you close to a highway exit before the move or father away now? Are there more traffic lights or more traffic? These effects can easily have a 10+ percent effect on your fuel economy.

I've thought about the driving, for sure.

I'm 25% closer to the highway than I was before (was 4.5mi, maybe 3-3.25mi now). Traffic flow on both portions is/was similar, few stop lights, good flow, reasonable speeds, similar terrain, etc.

I've cut down my highway driving distance, but things have also been clearing up (for the most part) WRT traffic. And I'm driving, I think, a bit more conservatively (lower overall speed, but I used to go way too fast).

I dunno. I continue to think about driving in general, but I'm going to - as mentioned - polish off this (sadly new) tank o' fuel and try a different station for the next 3-4 fills. If it changes, it changes. If not, off to another potential fix.

 

[sirpuddingfoot]

Well, we have some positive preliminary indicators after running a can of Lubro Moly diesel purge. It was poured in the tank after the fuel low indicator light came on. The car was run through the rev range, idled, highway pulls, etc.

Survey says: mpg is at least partially back. My wife reported an astonishing (really, I cannot truly vouch for this kind of incredible success as a cure-all before completing a couple tanks, plus I really had to draw out the suspense by making this ridiculously long parenthetical aside) 37.2 in city driving on her way to work (on the computer). She has been getting between 28 and 32 for the last couple weeks, mostly in the 28-30 range. Beyond that, we have been struggling to get to 35 on the highway. I may have to run the second can I bought directly.

In any case, this <$10/can treatment is a definite must try before spending serious cash. And best of all, my local Napa stores are now putting it (and the other lubro-moly and Pentosin products) on the shelf.

 

[truman]

Can you do the diesel purge directly at the filter on a PD?

 

[Biodezl]

DieselPurge and FM100

I've been meaning to upgrade the fuel filter for a while and already had purchased all of the FM100 fuel filter components along with DieselPurge fuel treatment. Upon hearing of sirpuddingfoot's success, and to address my somewhat less-than-average fuel economy (around 33 mpg with 39.2 mpg max at 60 mph) and to address both "surging" and "slow acceleration below 1900 rpm" issues, I got the job done. (See the FM100 thread in this Passt B5 forum.) It is probably too soon to tell, however; there has not been much change in economy, nor acceleration, but the surging has improved. It is very smooth-running now, to be sure. Clearly the new filter and DieselPurge treatment impacts are comingled, but part of the issue was fuel-supply and/or injector clogging related.

 

[traubenberg]

I am simply not confident enough in my hands listening to my brain to do the FM100 filter upgrade. I applaud you (and the others that have done it, as well).

 

[Wizard]

Well I cleaned my MAF today as talked about here...
then took a little non-scientific 50mi ride .
Maybe it was me wanting it to, but it did seem a little pep'ier and I did avg. 36mpg.
I'll know more when I do the 270 to LA. on wednesday.
Still need to get timing checked.

Well here's an update.... On the first tank after the MAF cleaning MPG=34.23, which is slightly above normal but about average due to being mostly highway.

On the second tank since the MAF cleaning MPG=37.29, which is well above average.

One side note.... Between the first tank and second tank I changed belts, idler pulleys and the alternator pulley. While all seemed in good condition, I guess there is a possibility of extra parasitic drag from the old pulleys.

 

[Biodezl]

I am simply not confident enough in my hands listening to my brain to do the FM100 filter upgrade. I applaud you (and the others that have done it, as well).

You might want to take a look at the simplified installation instructions that I posted a few days ago on the FM100 thread. This was the easiest mod I ever did, after the air filter screenectomy and other silly stuff, of course.

...back to the regularly scheduled thread topic...

 

[sirpuddingfoot]

We ran another can of the diesel purge through the system (put the can in after the light turned on, drove ~50 miles before filling).

Indications are strong that this was our problem (the last tank averaged over 37mpg, I forget the exact figure now, 40% City, 60% highway). Driving around last night suggests we're on target for a >38mpg tank now. I have noticed the the MFD trip average increases much faster than it had been early in the trip. It used to climb slowly to about 25 and then struggle up from there. Now it shoots up to 34 over the first 5 minutes (getting to the freeway) and then increases from there.

This anecdotal evidence gives me more of an impetus to do the fuel filter upgrade.

 

[truman]

We ran another can of the diesel purge through the system (put the can in after the light turned on, drove ~50 miles before filling).

Indications are strong that this was our problem (the last tank averaged over 37mpg, I forget the exact figure now, 40% City, 60% highway). Driving around last night suggests we're on target for a >38mpg tank now. I have noticed the the MFD trip average increases much faster than it had been early in the trip. It used to climb slowly to about 25 and then struggle up from there. Now it shoots up to 34 over the first 5 minutes (getting to the freeway) and then increases from there.

This anecdotal evidence gives me more of an impetus to do the fuel filter upgrade.

What's your typical speed that you try to maintain on the highway?
On my drive to work, I find that if I stay at about 65, the trip average will be about 38. If I drive 70-73, it drops to about 34.

 

[oilhammer]

What's your typical speed that you try to maintain on the highway?
On my drive to work, I find that if I stay at about 65, the trip average will be about 38. If I drive 70-73, it drops to about 34.

No way I can keep a B5 TDI at 65... too slow for that car! (maybe if I left it in 4th gear...) Heck, at 80 it feels like you could get out and walk!

 

[s4phillips]

...On my drive to work, I find that if I stay at about 65, the trip average will be about 38. If I drive 70-73, it drops to about 34.

Maybe this explains why our average mileage is about 34MPG.

 

[sirpuddingfoot]

What's your typical speed that you try to maintain on the highway?
On my drive to work, I find that if I stay at about 65, the trip average will be about 38. If I drive 70-73, it drops to about 34.

We average about 8 over the limit. Most freeways in the Twin Cities area are 55. Beyond that, most highways in MN are 55. Freeway is anything from 60-70 out of the city.

The trip indicating we are talking about a 38+ tank was about 16 miles: 1.5 miles to the highway with 3 stoplights. 3 miles of highway and a short detour with a long stoplight to avoid a construction slowdown, then a couple more miles to the exit and another 1.5 to the stop including yellow light racing and 15-20mph construction/pedestrian zone cruising (Grand Avenue in St. Paul). Drive home was the reverse (minus construction slowdown detour) and an MFD average of 37.8. 2 weeks ago, I would have expected 28-29 for that trip.

 

[aja8888]

What's your typical speed that you try to maintain on the highway?
On my drive to work, I find that if I stay at about 65, the trip average will be about 38. If I drive 70-73, it drops to about 34.

Yesterday I ran from south of Dallas to north Houston and had it (the cruise) set on 80. A couple of bumps up to 95 on long stretches to get the cobwebs out. I'm not checking the MPG on this tank. This car really runs nice over 80.... Plus, it idles a bit smoother after 200 miles a that pace.

 

[truman]

Yesterday I ran from south of Dallas to north Houston and had it (the cruise) set on 80. A couple of bumps up to 95 on long stretches to get the cobwebs out. I'm not checking the MPG on this tank. This car really runs nice over 80.... Plus, it idles a bit smoother after 200 miles a that pace.

For comparison sake, what is your MPGs at that average speed- 28 or so? Inquiring minds want to know.

 

[aja8888]

For comparison sake, what is your MPGs at that average speed- 28 or so? Inquiring minds want to know.

My overall average for over 40,000 miles is 33.3 MPG. When I run a partial tank at those speeds, it is around 30, but if it were the whole tank, I would guess around 28.

I have 17" Bistars and typically have the A/C on here in Texas. Plus, I drive it pretty hard when the road is open as that is not a problem for these engines.

 

[truman]

My overall average for over 40,000 miles is 33.3 MPG. When I run a partial tank at those speeds, it is around 30, but if it were the whole tank, I would guess around 28.

I have 17" Bistars and typically have the A/C on here in Texas. Plus, I drive it pretty hard when the road is open as that is not a problem for these engines.

Thanks, mine rides on 205/60/16 nonLRR. Initial warm up time, stop and go, and speed kill MPGs much more than on my previous ALH. It appears that your FE is very close to mine. My average is also close to 33.

 

[spiceredwagon]

Four tanks after fixing the torsion adjustment I see no difference in the mileage trend.
Most tanks come in at 6.6 l/100km as usual.
For the minority of the world that use unique USG's that translates to 39.9usmpg.

 

[thundershorts]

perhaps if the timing was set to value that your engine was at prior to bsm upgrade, you would be able to make a more valid comparison. running with syn oil, i doubt that much break in wear will be incured.

 

[dhuddleson]

Have not yet verified the Torsion value on my car after the BSM job a year ago. Economy had not seemed to change after the BSM and TB work. However fuel economy seems to have dropped 1-2 mpg just this summer/fall, even after an oil change and filter service was performed in the summer. So I ran a can of the Diesel Purge through yesterday on a nearly empty tank, and drove it around at least a 1/2 hour of mixed driving before filling the tank. Steady-speed readings do seem better already. Will report back after a couple of tankfuls.

And for those in Ottawa area, RJ Motors in Kanata will now be keeping some of these LubroMoly Diesel Purge bottles in stock.

 

[whizznbyu]

I'm sure this next post is ALL IN MY HEAD, but since the last fill up from a different gas station, I'm hitting 39 when it was at 42. Same road, same driving style, same traffic pattern.

 

[stefhelm]

Been a while since anything has been said here. I checked out my passat today and found the torsion value at -1.5. Got it to 0 and the car seems to have less vibration at idle. Not expecting much for mileage, but glad that there was positive results.

 

[50harleyrider]

Been a while since anything has been said here. I checked out my passat today and found the torsion value at -1.5. Got it to 0 and the car seems to have less vibration at idle. Not expecting much for mileage, but glad that there was positive results.

Mine was-1.5 too and changed to 0. Why isn't it just called cam timing? I put these pulleys on my mini stock Pinto powered stock cars back in the 80s.

 

[50harleyrider]

set at 0 seems to make the car run better overall.

 

[Biodezl]

I've been wondering if a different torsion value is appropriate when running high-concentration biodiesel like B99 or B100. Since biodiesel takes slightly longer to burn, perhaps a slightly advanced torsion value would recover some of the lost pep and fuel efficiency many have experienced...including me. Has anyone tried this and found an improvement?

 

[tikal]

set at 0 seems to make the car run better overall.

Except that some riders with Frank's reprofiled stage II cam report better mileage when torsion is set to somewhere between -3.0 and -4.0

 

[50harleyrider]

I've been wondering if a different torsion value is appropriate when running high-concentration biodiesel like B99 or B100. Since biodiesel takes slightly longer to burn, perhaps a slightly advanced torsion value would recover some of the lost pep and fuel efficiency many have experienced...including me. Has anyone tried this and found an improvement?

I'd really like to do some tests since I'm running B75-100 this summer. I'm running about 75% city now so it would be tough to get any useable numbers. My "torsion" was at -1.5 and is now at 0 and it does feel stronger. I'll try it at +1.5 and report back. Why don't you try +3 and let us know your results. My wife's car has a Franc06 cam so I'll try hers at +3. I'll have to ask vwtzips which one.

 

[50harleyrider]

I'd really like to do some tests since I'm running B75-100 this summer. I'm running about 75% city now so it would be tough to get any useable numbers. My "torsion" was at -1.5 and is now at 0 and it does feel stronger. I'll try it at +1.5 and report back. Why don't you try +3 and let us know your results. My wife's car has a Franc06 cam so I'll try hers at +3. I'll have to ask vwtzips which one.

vwtzips has done some tests with the stage 2 cam in my wife's car probably on petro diesel. They concur with Tikal. Look here: http://forums.tdiclub.com/private.php?do=showpm&pmid=2668209