Drastic drop in MPG

[This_Fuggin_Guy]

A little background, I purchased a "new" 2015 Golf Sportwagen, 82 miles on the clock, back in April as my new position required me to travel a lot more and the 17 mpg I get in my S6 was raping my wallet. My commute to work consists of about 74 miles a day with about 66 miles highway and 8 miles back roads/traffic lights. I carpool with a coworker who lives in town so I only have to fill up about 1-2 times a month and I mostly use the TDI for work and the S6 for around town and what not.

I was averaging between 50-53 mpg per fill up, (actual calculation, not based on what the dash says) but I have noticed that my mileage has been dropping rapidly and drastically. My last 5 fill ups, which go back to the beginning of November are, 47, 47, 45, 44, and then last nights, 39 mpg. I understand that mileage always goes down in the winter but dropping over 10 mpg seems like a lot. This is my first diesel so is this a normal drop in mpg for the winter? Is there something I should be doing to help with the fuel consumption in the winter time?

As far as the weather goes, this week it has been the coldest, dropping down to 10-12*F when I leave in the morning but the last few weeks its been high 20's to low 40's.

 

[turbobrick240]

It's normal. Not only is the engine less efficient in the cold, but winter blend diesel has lower energy density. You might want to check your tire's pressure- it drops in cold weather and contributes to lower fuel efficiency.

 

[VeeDubTDI]

Totally normal. Expect a 20% drop in fuel economy in cold weather like this. Expect an even larger drop (up to 50%) if you take short trips in this weather. Our Passat can get 50 MPG on a good day, but I can get it down to the mid to upper 20s in single digit weather if my trips are less than 5 miles.

The reason is because it takes a lot of energy to get the engine and emissions systems up to temperature. Most of that energy is expended in the first 10 minutes of operation. The longer the drive, the less overall impact it will have. The shorter the drive, the more overall impact it will have.

 

[tdidieselbobny]

Yep, also adblue consumption is increased. I filled up today and noticed they jacked it up 10 cents to $2.959. I think this tank was just under 37mpg.....

 

[IndigoBlueWagon]

It's funny, for years people complained about poor heat generation from rotary pump TDIs, and how they didn't like winter. Now the new cars warm up and produce heat much faster, and start much easier, too. But it's at a cost in fuel economy. Can't have everything.

It's about 10F here today and my ALH was barely up to operating temperature after running at 75 MPH for about 10 miles. And as soon as I got off the highway it started to cool down. The '15 doesn't do that.

 

[dubStrom]

block off the raqdiator

It will help to place a perforated piece of cardboard in front of the radiator. Helps a lot, actually. You just have to deal with the cold weather while you do it if you didn't think ahead

 

[WhatFloor]

Use the engine block heater, wear warm ****. Drive for the first 20min without any heat (turn on for 30s-1min only when driving if windshield begins to collect water vapour). It sucks but it will help your economy. Good thing those seat warmers are effective! I've noticed having the heat on while stopped at a red light = the kiss of death. You can watch the gauge go down, pretty funny. You can put the oil temp on your heads up display, that is what I watch when I am driving. I used to drive fast and aggressive, so hypermiling keeps me out of trouble now

 

[This_Fuggin_Guy]

Thanks for all the quick replies.

It's normal. Not only is the engine less efficient in the cold, but winter blend diesel has lower energy density. You might want to check your tire's pressure- it drops in cold weather and contributes to lower fuel efficiency.

Yup, I keep a close eye on the tire pressure once the temp starts to drop.

It will help to place a perforated piece of cardboard in front of the radiator. Helps a lot, actually. You just have to deal with the cold weather while you do it if you didn't think ahead

I will have to try that, thanks.

Use the engine block heater, wear warm ****. Drive for the first 20min without any heat (turn on for 30s-1min only when driving if windshield begins to collect water vapour). It sucks but it will help your economy. Good thing those seat warmers are effective! I've noticed having the heat on while stopped at a red light = the kiss of death. You can watch the gauge go down, pretty funny. You can put the oil temp on your heads up display, that is what I watch when I am driving. I used to drive fast and aggressive, so hypermiling keeps me out of trouble now

I usually drive for a while with the heat off or very low, the guy I carpool with complains because its so cold. I just tell him to bundle up and quit his crying.

It's funny, for years people complained about poor heat generation from rotary pump TDIs, and how they didn't like winter. Now the new cars warm up and produce heat much faster, and start much easier, too. But it's at a cost in fuel economy. Can't have everything.

I can deal with it taking a bit longer for the cabin to warm up, I'd much rather have better gas mileage.

 

[740GLE]

No coolant heaters on the US spec. So best bet is keep the cabin heat to a minimum and look at a winter front.

 

[turbobrick240]

No coolant heaters on the US spec. So best bet is keep the cabin heat to a minimum

That's pretty hardcore. When it's -20°, my own & passenger comfort takes precedence over a pint or two of fuel.

 

[aditud]

Yep, I posted a similar experience here http://forums.tdiclub.com/showthread.php?t=421919&page=45

I used to drive an un-fixed 2015 GSW SE DSG before my current 6MT, and the hit in fuel economy due to cold weather wasn't this serious. I'm suspecting the "fix" contributes to poor cold weather FE.

 

[Grigg3]

I have 10,000 miles on mine now, with 6MT.
Average MPG 46.6
48.2 MPG last tank after several days driving at and well below freezing, previous tank was 48.6, also cold, less highway driving.
Best MPG 50.9 back in May on long trip, not many hills.

When possible I put it in the garage and plug in Frost Heater for about 4 hours before leaving. Otherwise it does struggle a little to get up to temperature from a cold start and gentle 10 mile drive.

I’d say not much trouble or lost mileage in winter.

 

[marcusku]

I don't think there's any way out of a FE drop in the winter. Takes more energy to warm up the block, tires, bearing grease, etc. are stiffer, air is more dense--increased air drag. I find I'm losing 5-10 mpg in the winter depending on how cold it is which is similar to my ALH in the winter.

 

[aditud]

I don't think there's any way out of a FE drop in the winter. Takes more energy to warm up the block, tires, bearing grease, etc. are stiffer, air is more dense--increased air drag. I find I'm losing 5-10 mpg in the winter depending on how cold it is which is similar to my ALH in the winter.

I get it, but my point is that it was more like 3-5mpg less in the un-fixed GSW, whereas now is like 6-10mpg.

BTW, car is parked in the (unheated) garage at home. But event in the most frigid conditions here in the Pittsburgh area (like this past week), water never freezes in my garage (back wall is underground and right wall and ceiling are shared with heated rooms). So, I'm not even talking about starting the engine outside in the parking lot when leaving work and 0F outside, that would not make it so surprising. I'm talking about leaving my always above freezing garage and driving to work. Last time I did it (last week, maybe 18F outside) I only managed 39.5mpg. I was like "what???".

I spent last Fall on sabbatical in Wisconsin and my previous GSW DSG was outside (no garage) from July to until about Xmas. And when the first frigid front hit (around 0F) I still managed over 40mpg from Madison to Sun Prairie, even though it was a short, 20mi drive.

So, when they say "the modification will not affect FE", I think they mean it "under normal driving conditions" (not cold weather).

 

[turbobrick240]

I don't think there's any way out of a FE drop in the winter. Takes more energy to warm up the block, tires, bearing grease, etc. are stiffer, air is more dense--increased air drag. I find I'm losing 5-10 mpg in the winter depending on how cold it is which is similar to my ALH in the winter.

Yeah, short of moving to Miami, Brownsville, etc., lower efficiency in winter is pretty much a given. I honestly haven't even been thinking of FE during the last week of subzero weather here. Just glad the car starts and makes decent heat after several (or more) miles.

As an aside, at -20°F, my jug of Delo 5w-40 was pretty syrupy. The jug of 30W bar and chain oil was like thick molasses.

 

[IndigoBlueWagon]

My rotary pump TDIs usually would see about a 10% drop in FE in the winter. And in some more extreme cases it would go lower. My cars are inside at night in a garage that doesn't get to freezing temps, and I use winter fronts.

My average so far in my GSW is about 42.5 MPG. Current tank is showing about 38. Sounds like a 10% drop to me. And the car makes heat almost immediately, which I appreciate.

 

[Ronner]

I logged my first under 40mpg calculated entry last week. Considering the frigid temps, snow and slush covered roads and, at times, screaming winds I'm still quite pleased with my first diesel.

Today at the fuel pump the pump really did not want to start pumping, it kept clicking off. It was "blistering" cold this morning.
It took a couple min. to pump a couple dollars worth. Was ready to hang it up when it finally started to move. It was the most apprehensive tank of fuel I've ever pumped, wondering if I've pumped a bunch of wax into the tank.

Gone 100 miles since with no issues so I feel a little better about it.
Used an additive and kept a receipt so will see what happens...?

 

[This_Fuggin_Guy]

Correct me if I'm wrong, no one make a winter front for these cars yet, correct?? Everything I've seen/read has been DIY.

Either way, I have to laugh at myself, I was happy as a pig in sh*t anytime I got anything above 17mpg in the S6 but now if I get anything under 49mpg in the TDI I get worked up. Even at the most recent reading of 39mpg, that's still worlds above the mileage in the S6 and I'm still not happy. HAHA

 

[Ronner]

I'm making a new years resolution to stop watching the fuel consumption cpu. I'll avoid braking, be light on the pedal, not tailgate, coast as much as possible and simply know I'm getting the best fuel mileage of my life without even looking.

When the tank gets below half look for the cheapest price and top it up.
And STOP obsessing about it! hahahaha.

 

[tdidieselbobny]

Correct me if I'm wrong, no one make a winter front for these cars yet, correct?? Everything I've seen/read has been DIY.

Either way, I have to laugh at myself, I was happy as a pig in sh*t anytime I got anything above 17mpg in the S6 but now if I get anything under 49mpg in the TDI I get worked up. Even at the most recent reading of 39mpg, that's still worlds above the mileage in the S6 and I'm still not happy. HAHA

I know the feeling.... and it makes you even more p*ssed when you drive by the place you fill up and see they jacked it up another 10 cents a gallon(20 cents over a couple weeks now).....

 

[740GLE]

Our two local stations near our house Shell and Irving actually ran out of all blends of unleaded and diesel yesterday, apparently people wait until the last minute to fill up. Before they ran out, Diesel was 2.80 on the way to work, it was 3.01 on the way home.

 

[IndigoBlueWagon]

https://www.youtube.com/watch?v=i6zaVYWLTkU

 

[adjat84th]

https://www.youtube.com/watch?v=i6zaVYWLTkU

I manage a grocery store, can confirm the chaos of these events. My area typically doesn't see snow like this, but we did actually get 8-10" overnight with higher drifts all over. I've never gotten stuck in either of my TDIs, hopefully I can continue that run!