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Disappointing fuel economy '13 TDI while towing

13K views 83 replies 19 participants last post by  NTDI 
#1 ·
I have been towing my 6800 pound enclosed race car trailer with my '06 V8 Touareg for a few years now and have been getting 7-8mpg.
We recently bought a '13 TDI Touareg and I have towed the same trailer to two races now and the best so far has been 10.6 mpg. Terrain is rolling hills in Nebraska, Kansas and Oklahoma. Not a whole lot of elevation change. Was expecting 12-14 after reading lots of posts on this forum.
The other issue with towing with this TDI, is passing. First time I went to pass someone, was scary. Sure it down shifted to 4th, but then had no get up and go to make the pass like my V8 would.
Anybody tow with a similar weight trailer and notice the same issues? Since I bought this post fix, I have nothing to compare it to.
 
#4 ·
My ‘13 exec TDI gets 10.5-11.5 mpg towing a 24’ x 8.5’ car trailer. Mileage is the same as an ‘03 Duramax.

I’d love to know how the V10 got better mileage.

Square front trailers have a lot of air drag. In fact I find it tough to go faster than 62 mph while towing this trailer.
 
#7 ·
That's interesting. How many mile trip average is that?


I did a 1500 mile trip and couldn't get much better than 11 MPG. It makes me wonder if there's something wrong with the engine or trans.


Do you tow in Drive or Sport mode?


Unfortunately I bought my vehicle from the dealer last year post fix. I didn't think 10.5 MPG was unreasonable since the trailer is 24' and probably weighs 5000 lbs or so, and 10.5 MPG is what a Duramax got towing the same trailer.


I guess to be fair on the flat I was doing 60 - 65 MPH. However I can't remember if I got to 70 MPH ever (I might have).





Towing a smaller U-haul trailer I got 18 MPG which I thought was pretty good. But the big trailer has a lot of frontal area and drag so I thought 10.5 seemed average/normal.


I'd really like to know more about how you got 13-16 MPG. Perhaps there is something not operating properly on my vehicle.



I suspect there might be an efficiency hit in the 3.0L V6 for higher HP output compared to the older V10s which have (I think) dual turbos and more cylinders to extract power from... but to me it'd be hard to imagine better than pickup truck efficiencies from a 5.0L pulling a large enclosed trailer. I would think drag takes HP to over come and there isn't much of a way around it.Then again maybe I'm missing something here....
 
#8 ·
I've towed that rig 34,000 miles of the 74,000 now on the car (with zero repairs BTW). 2,000 lb aluminum V-nose trailer with 3,500 lb load. Atlantic to Pacific and Gulf to Great Lakes multiple times by all routes. Nothing changes. Always in D, except for downhill engine braking. Set the cruise control and relax in the right lane.

The trailer is not as tall as some (mid-height of the three Trailex options), so somewhat less frontal area than a full height trailer.

I don't believe the V10 can come anywhere close to the V6 in fuel economy.

Are you sure your trailer brakes aren't dragging? ;)
 
#9 ·
What kind of speed are you cruising at?
Does the tranny shift all the way into 8th, or are you holding 6th\7th?
I towed a TT (way less aero than you) at a suspected ~4500 lbs and got 13mpg cruising at 68mph manually shifting to 8th.
I would suspect you should get close to 12mpg with a somewhat aero trailer if you're staying close to the 60mph speed.
 
#12 ·
It would shift to 8th on downhill runs. Slight uphill runs were mostly 6th or 5th. I do have the pre fix transmission code from yrktreg.
I meant to look at the end of the trip to see what the average mph was, but forgot. I would think it would have been about 55 to 60 mph. Most of the speed limits were 60-70 mph but generally I wouldn't be going 70. On the way down to Kansas we only got 8.8 mpg, but also had a good headwind.

I'm not getting any fault codes, but suspect that I'm not getting all of the boost from my turbo. Since there is less boost, the motor has to work harder to tow and therefore getting worse fuel economy. Would also explain the slow passing speed.

Going through a bunch of posts on here about EGR problems and carbon buildup and hoping I can find something along those lines that would explain my issues.
 
#20 ·
Just cleaned it up on Friday and my wife has been driving it since then. Thing is that fuel mileage without towing has been about 25 mpg with a high of 29 in mixed driving before I cleaned it up, but that is with light acceleration to try to get the best mileage. Pulling the trailer takes a bit more throttle and more airflow through that restricted intake, so I imagine now that it's cleaned up and less restricted, I should get a bit more fuel economy.
I will probably put my vacuum pump on some hoses and see if I have a leak.
I can't believe I haven't gotten a check engine light with all that carbon buildup.
 
#21 ·
Did a log before I cleaned up the carbon and saw that commanded boost was to be 1000 hPa and actual was 972. That is only .5 psi than commanded, so probably within spec. Also saw 603 nm engine torque on one of my full throttle acceleration runs, which converts to 444 ft lbs.
 
#25 ·
Bought a 2012 Lux tdi this weekend. Test drive showed 24.6 average mpg. They performed the fix the next day and I drove 250 miles Chicago to Lansing... mpg average 16.4, no trailer. Can anyone explain this? Next day trailer test with 2000# Shasta camper, high and flat, showed 14.8mpg. Also note, while looking at aftermarket backup cameras I discovered this 2012 is more likely a Gen 2 vehicle as far as software. No versions are listed, simply MU software: 0319. Thoughts?
 
#26 ·
I bought a 2012 Lux TDI in 2015 with just under 124K. It spent most of its life until then as a freeway cruiser here in my adopted New York state and, apparently, New England. Before I sold it back to VW last November with not quite 149k it spend its time in short distance suburban low speed stop and go service outside of metro NYC with occasional freeway trips. Even with lots of idling in winter warm ups and at traffic lights my year round average mpg was, rounding off, in the 17-22 mpg range. When stretches of highway and interstate driving were included the mileage jumped to the mid 20s. On an extended trip to Eastern Canada and coastal New England where I tended to cruise in the 70-80 mph range, when road conditions allowed me to do so, I averaged 26-28 mpg with four passengers and a fully loaded cargo area.


Dealer Serviced during my ownership, I used the correct VW approved Castrol brand oil. Only Shell Diesel with their highest grade used when in Canada. If I was still in my home state of California, like I did with my former Golf TDI, I would have only used Chevron diesel. Tires inflated to VW specs. and under my ownership I fitted with Pirelle's Scorpion Verde All Season Plus tires when I first got the Touareg which it still had when I sold it back to VW.


VW considered my Touareg a Generation 1. As with my Golf TDI, the only reason I sold it back to VW was that the buy back offer was too good. I actually turned a profit and used the proceeds to pay off the bulk of my oldest daughter's college student loans. I replaced it with an Alltrack S.
 
#27 ·
Shasta,


Something seems off to me. What speed were you driving?


My '13 consistently gets 29.8 MPG highway at 75 MPH and up to 32 MPG at 60 MPH. Around town I average around 18-19 depending on how much fun I'm having and how bad traffic is.


As far as I know my '13 has had the fix performed. The only real change is DEF use from what I've read/heard. I find I have to top the DEF tank every 3,000 to 4,000 miles. Autozone and O'Reily's have DEF for $10-$12 per 2.5 gallon not a huge deal to me.




As to your mileage have you checked your air filter? Also may want to get a log of the sensors while driving if you happen to have a VCDs. It sounds like something is off somewhere.
 
#28 ·
12-15 mpg sounds legit when towing anything with some frontal area
Low to Mid 20s should be easily achievable on freeway driving if you're not towing and you don't have flat tires.....
Around town, city type traffic, you'll see 18-19 mpg......

If you've got soot buildup, or stuck intake flaps, or any other issues, your mpgs will suffer....

Are you seeing any codes?
Are your tires inflated properly?
Is the tranny shifting all the way into 8th?
What kind of RPM were you cruising at on your 250 mile trip?
 
#36 ·
I'm not sure if the Touaregs have an N02 sensor (they might). But I'm sure they have an O2 sensor (or two). O2 sensors can certainly effect the economy. A lot has to do with the base tune, altitude and the amount they are relying on the O2 sensor to optimize the a/f ratio.


Also what gears were you towing in and at what speed in each gear (were you in Sport mode)?
 
#37 ·
In my experience my Touareg V10 got better fuel mileage towing than my V6 TDI in either the T2 or T3. This is me actually towing with these vehicles extensively, not internet bullshit.

Personally I did not like the V6 TDI for towing, thought it to be really undesirable. For me the V6 TDI is the ultimate SUV engine...except for towing. Fuel economy towing in anything for the most part sucks...this is from my experience towing in Touaregs, F250/350 6.4 and 6.7 diesels and the latest 6.6 Duramax. Sorry to say it about the V6 TDI, but to me its never been a towing engine, its the ultimate road engine... feel free to flame away.
 
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#47 ·
I also don't want to flame, so I'm not going to single anyone out, but for someone who throws a title around more than they should, you say some really stupid crap sometimes..... do you get high right before you start posting on this forum or what? Controlled compression ignition is NOT the same as detonation..... but let's not hijack another thread.....
 
#52 ·
I agree. Also look at it this way. Other than the old V10 TDI what midsize suv are you going to find that can tow like the Treg V6 TDI. I can tell you... Notta.
There is no other midsize period. Well except maybe Ford Explorer eco boost. But fuel mileage want touch the TDI. Actually we had a Yukon V8 and honestly I still preferred the TDI. I tow up to 5k with mine and it’s a dream. Can’t compare it to the V10 TDI though as I’ve never driven one. I’ve had several other midsize SUV’s over the years and nothing touches the VW V6 TDI towing ability. I would think maybe a Explorer with the V6 eco boost? All I know of though.


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#56 ·
The only ones I can think of are the Durango, and Jeep Cherokee. Maybe some of the more expensive European suppliers have something but not sure. Jeep did have a diesel but I think they removed it due to a multitude of issues plus epa stuff. The Jeep and Dodge V8 gas engines get crap fuel mileage plus have the need for higher rpms to pull a equal load vs a Diesel engine.


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#57 ·
The only ones I can think of are the Durango, and Jeep Cherokee.
No thinking required. Click the link. But, yeah, Durango and Grand Cherokee are two of them. I wouldn't want either. Audi, Porsche, MB. Given the limited choices, I might step up to a Land Cruiser. 8,100 lbs. It's a pig though. Gets fuel economy of a TDI towing when it's not towing.
 
#58 ·
This weekend I had another race in Topeka, so the same route was used as it was in May. A little less wind.
Not sure if the carbon buildup was a problem because I only got about 1.5 mpg better average than last time on the way down.
On the way home I decided I was going to see how much better I could do by controlling the shifts myself. I kept in in 8th as long as I could going up the hills. I would downshift to 7th or 6th once 8th couldn't maintain speed at 2/3 throttle. Water temp stayed steady even with 90°F outside temps. Doing this, fuel economy went up to 12.5 mpg. Back in May, it was 9.8 mpg with slightly more wind.
And so you don't have to go back and look, yes, I have done the pre-fix transmission coding. Next thing would be a tune, but I don't want to screw with warranty.
 
#63 ·
I towed a 6x12' enclosed trailer rented from UHaul, and it was STUFFED. The trailer is rated for 4400lbs (GVW), and I think I was quite close to that. Has a nice very non-aerodynamic flat slab front end.



Anyways, I drove from SLC to OCMD in 3 days, cruise control at 70mph, and averaged about 17mpg. I didn't even make it Pittsburgh though before it was screaming at me for DEF. This tow happened post fix, I have no experience pre-fix towing, except for towing my RS4 from Idaho Falls ID back to SLC, which was like a 3 hour trip.. But I think I was getting 17+ on that too..
 
#64 ·
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