This MPG is crazy

Yesterday I got my best MPG ever since buying the car in December. I can't really figure out why. 330 miles, used AC about 2/3rds of trip, maintained 74-75 MPH except for construction zones. MFD said 52.2, hand calculated says 48.3. I fueled up at the same pump and pumped till I saw it in the top of the filler neck both times. My normal highway MPG has been 42-44. The only things different were 1. I bought fuel at Chevron for the first time 2. Tires were rotated, balanced and they put 34 PSI in them (checked cold in the AM) and I was running 33 PSI prior to that. I can't see how 1 PSI would change anything nor can I see balancing tires changing anything. Maybe the Chevron fuel has a higher cetane number?
Whatever it is I'll take it.

bigb thats great fuel mileage. ! I got a 2012 TDI Highline just like the one shown here except its black in colour with tinted windows i really like the Low end Torque it makes. fuel mileage im getting upwords of 47-52 mpg"s on the early morning commute to work Great Car.!! if You maintane these vehicles well. they will give You years of trouble free service.
https://www.youtube.com/watch?v=LFj_QgaEVvw

I googled it and was surprised to learn that balancing the tires does help fuel economy. Also I think all the fuel I have been buying has been either B-5 or B-20 and it's possible that the Chevron fuel is 100% dino. Have to start paying more attention to the pump label.

I get the best mileage with Chevron diesel here in CA. Use it exclusively for D2 fill ups.

If you draft behind a high profile vehicle at speed it will greatly improve your MPGs. Like 10-20% so keep that in mind. Wind, ambient temp or rain can also make a big difference in MPGs.

CleverUserName said:

I get the best mileage with Chevron diesel here in CA. Use it exclusively for D2 fill ups.

If you draft behind a high profile vehicle at speed it will greatly improve your MPGs. Like 10-20% so keep that in mind. Wind, ambient temp or rain can also make a big difference in MPGs.

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For now I am going to stick with the Chevron, the price was good too $2.99. When you draft a semi how close do you get? I followed one thru Phoenix but I stayed back a good 200 feet. Our roads are bad here and if you follow too close you won't see the potholes in time.

bigb said:

...Also I think all the fuel I have been buying has been either B-5 or B-20 and it's possible that the Chevron fuel is 100% dino. Have to start paying more attention to the pump label...

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Biodiesel has a lower Specific Energy than D2, so the higher the Bio blend you use, the lower your mileage will be.

Also bump the tire psi to like 38-40 ull see another 2-3 mpg gain.

Was this the first long drive in the car? IMO longer highway runs +100 miles is where the emissions system is happy and reaches it's passive regen point, thus higher MPGs, a 300 mile non stop trip will def skew those numbers higher.

On a recent trip up to western Massachusetts I did an experiment. Filled up just before getting on the highway and filled up again soon after our arrival. 90% highway and the rest on state roads with 45-55 MPH limits. I did the speed limit except for passing a couple of slow pokes on the back roads and did a hand calculated 54.4 MPG tank.

You may have gotten better FE, but the difference between 44 and 48 MPG for a trip that length is about 7/10ths of a gallon. Fuel foaming could account for a some of that.

I usually fill my cars at home (I have a diesel tank), and the fuel foams very little. I've noticed that the GSW has a vent-like behavior like the older TDIs, where if you fill to the neck and then wait a minute or two the fuel will drain down a bit and you can get a little more in. So that could be anther reason.

It'll be interesting to see what the next tank brings.

IndigoBlueWagon said:

You may have gotten better FE, but the difference between 44 and 48 MPG for a trip that length is about 7/10ths of a gallon. Fuel foaming could account for a some of that.

I usually fill my cars at home (I have a diesel tank), and the fuel foams very little. I've noticed that the GSW has a vent-like behavior like the older TDIs, where if you fill to the neck and then wait a minute or two the fuel will drain down a bit and you can get a little more in. So that could be anther reason.

It'll be interesting to see what the next tank brings.

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Yes I thought about that and tried to fill it to where I could see it in the neck just below the flapper. I guess this is where averages will come in and eventually I should have a pretty good average. So far I have only logged 13 fillups.

740GLE said:

Was this the first long drive in the car? IMO longer highway runs +100 miles is where the emissions system is happy and reaches it's passive regen point, thus higher MPGs, a 300 mile non stop trip will def skew those numbers higher.

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No, most of my driving has been highway with MPGs from 44 to 47. The hot weather is here now though.

I commute for work from Chicago burbs to Milwaukee every day, I can say I have learned my ways with the 15 GSW TDi S DSG. I have gotten 600 miles to a tank and put 12 gallons in. My 09 2.0T TSi has gotten as good as 34MPG on the same commute but I don't want to put the miles on her anymore because racekor. I've had the 15 GSW for 2 months now.

75MPH for half the trip ON cruise, 65MPH through the construction area and into Milwaukee were I pick up some slower traffic some times. I have seen my 75 mile commute average say 58.4MPG on the MFD once with a bit of tail wind.

I started tracking my MPG recently via Fuelly actually to see what she will do.

Now I want to tune it for even more MPG. Researching which one to go with, I might just do Kerma if Mike from TDT has nothing.

Car is 100% stock, has 16" alloys on it that are factory S wheels with unknown brand tires that are brand new and aired up to 38PSI. I use air conditioner because I don't want to bake in my white Maytag oven

Forgot to add, I fill up with Costco diesel in Pleasant Prairie, was 2.59 a gallon last week. Venting it and filling to the fuel cap !

I have a ClubTDi license plate frame on the back if anyone drives the same ways as I do

Born at Woodstock Hospital (Not the music festival) and lived in Crystal Lake growing up. Been out here in the desert more years than I can count though.

I stopped by the Chevron and sure enough their diesel is pure dino, no bio like Qwik Trip and Safeway. I am sure that has something to do with it.

My personal best was on diesel from Sinclair out of my 300 gal drum: 69.6 mpg on the MFD, 66.9 mpg hand calculated. The trip was 62 miles total, with a tail wind for about half of the trip. It was about this time last year, but I was also not running any AC.

My best so far this year was on Wednesday. Same trip, about 62 miles total, with a slight tail wind half the trip, and AC for half the trip. I calculated about 60.2 mpg, and the MFD reported 62.6 mpg.

On longer trips in the summer, I'm consistently running between 55 and 60 mpg. It drops to around 47 to 50 mpg in the winter.

I'm beginning to think Mk7's aren't too far off a stock Mk4. I have 15" wheels which helps too. My current tank is off to an exceptional start. Mostly highway, mostly between 60-70 mph. The construction zones really help with heavy traffic and slow speeds. I don't think I'll be able to maintain over 62 but we'll see what happens. I corrected the MFD and if anything it seems to read a bit low. Might have to try for 800 miles. The needle just dropped below 3/4 tank:

How many times do you guys need to read that measuring FE on short distances isn't indicative of overall FE? Not any more than a gauge reading like this on my MKIV.


The average over three tanks rule is still the more reliable measure.

Well said Peter.

Also what the car thinks the mileage is means almost nothing in comparison to an actual calculation of miles over gallons pumped.

I would agree if you're only putting in a gallon or two, that's tough to measure accurately. For a whole tank though if you fill it consistently I don't think you'd be off by more than a MPG. The MFD isn't perfect but mine seems to be within a mpg or two after I corrected it. My current tank isn't indicative of overall fuel economy, I've had usually good conditions. My last few tanks though have been in the mid and upper 50's which I believe is similar to what an stock Mk4 would have gotten in the same conditions. Actually on my Mk4 after staring at the fuel gauge for 300k miles, you could tell approximately what is was getting within a couple mpg. I imagine you can too unless you don't always fill it the same.

Some folks including myself get a kick out of getting an usually good tank.

marcusku said:

Some folks including myself get a kick out of getting an usually good tank.

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Yes, I am one of those folks, when I can make the trip to Northwest Phoenix and back in my VW for $17 and it costs $60 in my F-350 diesel I am ecstatic.

MFD is a bit off on my TDi. Says my average on tank is 53 but hand calculated it's 48.6.

AC on, cruise control and 75mph for about 40 miles and 65mph for 35 miles. What kills my average is my afternoon commute where I sit in traffic quite a bit.

Either way I am happy

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Long duration MFD MPG readings on the passat shows 49.5 MPG. Last 3 week of commuting 750 mile tank hand calculated to 45.6MPG. No complaints.

This is with stock phase 2 programming, I haven't snagged updated malone tuning yet.

I will add that at the OP's posted speed is where I've seen the best mileage on my 10 JSW too. Was kind of shocked since I've always thought of faster speeds as being worse for mileage. All this was before the fix and before buying our 17 Ram ED. Why take the JSW for long trips when we have something as comfortable as the truck and still get around 25 mpg?

Went on a trip to the Yukon with a college buddy from Toronto. On the way back, we had the A/C on full time. Still for the trip length from Beaver Creek, YT, to Anchorage the average was right at 50.0 MPG [4.7 l/100 km] and the road was pretty rough. About 450 miles [730 km.] Hi temp happened a couple of times at 29.5C and the A/C was very handy. I'm sure we could compete with those Phoenix potholes with our patchy permafrost and frost heaves.

I drove my car 4 blocks to the grocery store. When I checked the mileage, whoa, it was 134 mpg. Hard to believe this car can do so good!

Of course Fuelly shows my tank after tank average to be 35 mpg, but who cares about that.

Some of you folks are interestingly touchy about mpg reports. It seems that now my engine is seated, I'm getting better fuel economy than ever with a 54 mpg average over the last year.

That's great! Is that a hand calculated value? What % highway driving?

Miss_Athanatos said:

Some of you folks are interestingly touchy about mpg reports. It seems that now my engine is seated, I'm getting better fuel economy than ever with a 54 mpg average over the last year.

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On road trips I'm able to get mine around 48 mpg hand calculated, just keeping my foot out of it but still keeping up 70-80mph. Not bad considering, but in town and short trips sure are a lot worse than the ALH