Winter MPG - how much decrease is normal?

[digdug]

2013 6speed manual Jetta
for the past month I've been averaging only ~37mpg (commute is mixed driving, maybe 60-70% highway)

Prior to that I would average around 42-43mpg. Best tank I've ever had was around 46mpg (was in September).

Is that a normal hit to expect? Sometimes as much as I love the TDIs (I had a 2002 before this one), I think maybe a gasser econobox might have been a better value

 

[peobryant]

I've only had my TDI for about a month (purchased it on December 10th, 2014) so I am by no means extremely knowledgeable on the TDI in general, however I have been driving a '91 Cummins since I was old enough to drive so I have experienced quite a few winters with diesel engines.

My TDI had previously been getting 44-45 mpg when the weather was in the 40's or so, the tank before last was actually my personal best at 47.5 mpg. Right after I filled up the temperature took a fairly extreme drop, going from mid 30's and 40's to 0 F and below in about a day or so. I filled up yesterday after driving with that temperature for the whole tank and without changing my driving habits or route, I dropped to 42.5 mpg.

I have consistently noticed drops in mileage when the weather gets extremely cold in my Cummins as well. I would go from averaging 20-22 mpg in my '91 dually to 16-18 mpg when the cold spells came.

 

[digdug]

Thanks - I never noticed the drop in MPG on my 2002 , pretty much because it was an automatic and I never really kept a history on what it was getting for mileage. On that 2002 I'd base mpg if the car got at least 400mpg on a tankful. Even in winter that car would do that as lousy as that is for a ALH tdi.

 

[IndigoBlueWagon]

ALH's do lose FE in winter, but the newer cars lose more. They expend more fuel in warm up to heat up the emissions equipment quickly, and have more electrical losses (heated seats, electric cabin heater).

I find winter fronts on both cars help. I've been getting 46 pretty consistently this winter in my ALH driving mostly highway. My Golf on short trips in the winter will get around 40, whereas I see 43 or so in similar driving in summer.

 

[digdug]

ooops!!!! I meant 400 miles for the tank I'd get
sorry I had too much 5 hr energy pre-gym workout when I posted that

400mpg?
I'll have what he's having!

My bew drops 15-20% in winter almost like someone turned a economy switch to off.It's very noticeable.Thats more to do with the ecu putting in a extra bit of fuel to warm the engine up from 0F.
Im going to be installing a webasto which will help getting the engine up to heat lot quicker and will be able to see out my windshield for once

 

[RebelTDI]

Shorter commutes are much more affected than long, highway hauls, for obvious reasons. I am happy to say, though, that my diesel-guzzling 2010 CR TDI with snow tires on got 50 mpg on a trip from Boston to Philly down I95 with 4 people and luggage over the holidays. Driving around town, more like low 30s.

 

[psd1]

Lots of good reading here.

http://forums.tdiclub.com/showthread.php?t=394790

 

[Mike in Anchorage]

You can make things best by being aware of your use of large electrical loads [are your side mirror heaters left on continuously?] and by blocking the front air flow. These are all good suggestions, and you'll make improvements by using them.

Fuel economy in winter is dependent on many things. Each state has its own standards for anti-gel additives by month and that impacts fuel economy, at least here in Alaska, by about 10 to 15%. Worst months are January and February. What a person gets in Arizona, Texas, and California will not begin to compare with effect you may see in upstate NY, Montana, or in Minnesota.

 

[VeeDubTDI]

A 10-20% loss is normal in winter. Fuel economy will suffer more if you make shorter trips, as the warm-up is the big killer.

 

[2.2TDI]

A 10-20% loss is normal in winter. Fuel economy will suffer more if you make shorter trips, as the warm-up is the big killer.

This... I've seen a hit of up to 30% in the last month due to cold temperatures and mostly short city driving. Was getting 45-47 mpg a month ago on 90% highway driving. This tank it's looking like I'll get 37-38 mpg doing 75-80% city driving

 

[psrumors]

We took a trip yesterday where I would normally get 48ish mpg and I only got 42. Intake air temp was between 27 degrees and 36 degrees the whole trip. Seems anything below 40 degrees and my car gets "poor" mileage.

I've thought about getting a cold front for the car but really don't need one very often here in GA.

 

[Diesl]

I have been keeping track of my diesel mileage for the last two years, and see about 5-7% variation winter to summer; see the link in my signature. I do 40 mile commutes with ~1/3 city 2/3 highway.

 

[Wankel7]

2013 6speed manual Jetta
for the past month I've been averaging only ~37mpg (commute is mixed driving, maybe 60-70% highway)

Prior to that I would average around 42-43mpg. Best tank I've ever had was around 46mpg (was in September).

Is that a normal hit to expect? Sometimes as much as I love the TDIs (I had a 2002 before this one), I think maybe a gasser econobox might have been a better value

Block off the radiator and do a Frostheater and you might get most of it back.

 

[Cogen Man]

ALH's do lose FE in winter, but the newer cars lose more. They expend more fuel in warm up to heat up the emissions equipment quickly, and have more electrical losses (heated seats, electric cabin heater).

I find winter fronts on both cars help. I've been getting 46 pretty consistently this winter in my ALH driving mostly highway. My Golf on short trips in the winter will get around 40, whereas I see 43 or so in similar driving in summer.

Best mod I have done is a winter grill block for my 2011 Golf TDI from IDparts.com. Big reduction in engine warm up time on a stone cold engine. That equates to better FE overall. The big hits to FE for me are winter fuel, winter tires, cold temperatures(the grill block helps with that). I try not to use the heated seats but if you got them why not use them. Toasty buns are a good thing.

 

[Wankel7]

I block off airflow to the intercooler too.noticed 2-3% difference

Interesting...do you block it at the IC or at the bumper inlet?

What kind of IAT are you seeing?

 

[ScottySK]

I block off the grille for the IC as well, IATs are about -15 when it's -30 ambient. I also block off the cold air inlet and open up the intake tract to the warmer engine compartment. Still pulling 700 mile tanks (5-5.2L/100km) with my 16km commute in -30C or worse weather.

 

[tedd]

Same as Scotty, block the grill off. the temps depend on temps outside and gradient . just crusing on the highway -15c sees around -5c to 0c average on intake temp but it does vary. Never really see anything above 14c inlet until outside temp is in single + figures or going up a long hill. but nothing i would worry about in the slightest.

I know it's a gasser but i used to drive my 1.8t during winter the fuel economy would drop 20-25% because of the massive IC and 102 octane fuel it ran on. Boarded up 50% of ic/rad and ran it on normal unleaded. About 7-9% of the FE returned.

can you post pics of the grill block in action.
thanks.

 

[ScottySK]

I use a clip-in insert that clips into the grille and blocks it off.

Like this one:

 

[Steve Addy]

I need to do something, going to get some coroplast and make a grille cover, upper and lower. My normal mpg is 50+ but the nasty winter blend and weather conditions takes it down into the low 40's.

Steve

 

[ScottySK]

Where did you get the passenger side clip on Scotty?

Came with an extra bumper cover I picked up.

Concept-1 has one available for purchase: http://store.concept1.ca/Jetta-4-Bumper-Grill-RIGHT-KEYVW1036103/

 

[SkeeterMark]

ALH's do lose FE in winter, but the newer cars lose more. They expend more fuel in warm up to heat up the emissions equipment quickly, and have more electrical losses (heated seats, electric cabin heater).

I find winter fronts on both cars help. I've been getting 46 pretty consistently this winter in my ALH driving mostly highway. My Golf on short trips in the winter will get around 40, whereas I see 43 or so in similar driving in summer.

Are you sure about this? Mine seems to heat up (actual coolant temp) WAY faster my friends ALH. My theory was recycling more exhaust kept more of the heat in and around the engine where the older models just send it on out the tailpipe.

I have been keeping track of my diesel mileage for the last two years, and see about 5-7% variation winter to summer; see the link in my signature. I do 40 mile commutes with ~1/3 city 2/3 highway.

I concur with Diesl, and keep similar stats.

Winter fronts help, but I still think the OP is in the ballpark for "normal" winter vs. summer mpg.

And don't think for a minute a gasser does not suffer as well. Some even worse because more people are inclined to let them "warm up" for long periods of time. More so than us diesel drivers, since we know we have to get going to produce any significant temp increase.

 

[IndigoBlueWagon]

They do heat up faster, but it takes fuel to do it. And the electrical losses are greater, so FE suffers more. ALHs are cold longer, but don't expend as much fuel trying to get up to temperature. At least that's my experience.

 

[petee_c]

I've seen a big drop in Fuel Economy in the past couple months. This is my 1st winter with a 2006 Jetta TDI 5speed.

In September, I was averaging about 5.5L/100km, then in November I put winter tires on, and got probably about 5.7L/100km. It's been pretty cold the last few couple weeks in January. My 2nd last tank, I calculated about 6.4L/100km, and my last tank was over 7.0L/100km ( 28.xL/410km) I had a little more city driving than normal (trips under 20km) on the weekend as we were out and about a bit. The weekend was seasonably cold, but the last 2 mornings it's been near 0F on the morning commute.

Last night, I bought 12' of the black foam insulation for 1/2" copper pipe from Home Depot. Used it on the upper and lower grill. The needle on the temperature gauge got up near 90c in about 10km (6miles) of country driving. The car was in the garage and registered -8C on the dash, but the air temperature was -20C to -24C at work. I had a 80km (50mile) commute this morning.

Hopefully I'll be in the low 6L/100km range my next fill. Likely as I've got about 500km of almost all highway driving over the next 48hrs.

 

[VeeDubTDI]

They do heat up faster, but it takes fuel to do it. And the electrical losses are greater, so FE suffers more. ALHs are cold longer, but don't expend as much fuel trying to get up to temperature. At least that's my experience.

Right on the money. Commonrails end up wasting a lot of fuel warming themselves up, unlike the ALH which just freezes your ass off in the winter.

 

[pparks1]

I go from 40-44mpg on my tanks during nice weather to 32-34 on my tanks in the winter. I'm mostly city driving, lots of stop and goes, temps have been in the single digits, I run snow tires and have the DSG.

 

[Wankel7]

511 miles and a 49.1 MPG tank...not to bad in the winter! 80% 65 mph highway with equal head winds and tail winds.

 

[SkeeterMark]

Quote:
Originally Posted by IndigoBlueWagon
They do heat up faster, but it takes fuel to do it. And the electrical losses are greater, so FE suffers more. ALHs are cold longer, but don't expend as much fuel trying to get up to temperature. At least that's my experience.

Right on the money. Commonrails end up wasting a lot of fuel warming themselves up, unlike the ALH which just freezes your ass off in the winter.

So, according to what you've written here, the ALH uses just as much fuel to warm up (using less fuel per minute, but running time to get warm is longer, so probably equal), but is getting better overall FE due to the fact that it is not "guzzling " for the first part of the run to warm up.

I'm still not sure I'm buying into this one. I don't see any evidence that a commonrail takes a bigger hit on FE percentage-wise than an ALH due to cold weather.

In warm weather, does it take more fuel to idle a commonrail than an ALH (aside from being a bigger engine)? Not sure how you'd compare that straight up.

If so, would it then take even more fuel to idle a commonrail than an ALH in cold weather?

In any case....I like a warm car, lol.

 

[IndigoBlueWagon]

Who's talking about idling? If you idle an ALH in cold weather it'll be a long, long time before it's up to temperature. Hours. I was writing about warm-up time while driving. On a 20 degree morning my common rail will deliver heat within about a half mile of my house. Whether it's the electric heater, coolant, or both, it's hard to say. My ALH takes a bit over a mile before it gives any heat. And my ALH is modified and runs much more fuel than stock, so it'll warm up faster than a stock car.

The idea here is that because of the electrical devices in the new cars along with the ECU's efforts to quickly heat up the emissions equipment (read: fuel) that common rail cars use more fuel when coming up to temperature. And the winter FE numbers between my two cars bear that out. They weigh about the same, make similar power, yet the ALH consistently delivers better FE than the common rail when used for short trips.

 

[SkeeterMark]

I understood, I was just adding the idling question on top of the rest of the discussion. Sorry to add to the confusion.

But your statement "that common rail cars use more fuel when coming up to temperature" still is not registering with me. You say the AHL takes much longer to heat up. So are you saying in the shorter time period - let's say 5 minutes - the common rail is running to reach temp, it has used more fuel than the ALH which has run for - let's say 10 minutes - to reach temp? That doesn't seem right.

Note I'm not disagreeing with you, but rather trying to understand better.

I think what you mean is this:
Let's say the CR burns .2 gallons to come up to temperature, and it takes 5 minutes. It then burns .1 gallons over the next 5 minutes, for a total of .3 gallons in 10 minutes.

Now let's say the ALH burns .1 gallons per 5 minutes right from the get go, using a total of only .2 gallons over the same 10 minute time period.
Let's say they both use .1 thereafter.

In actuality, they both used .2 gallons to reach temperature, but the CR used it quicker and reached temperature quicker. So it's not using more fuel to get to temp, just using the same amount faster. For the full time period of 10 minutes it takes the ALH to reach temp, the CR used .1 gallons more than the ALH, but operated with heat 5 minutes sooner.

In this scenario, the ALH is achieving better overall FE, and bearing out your short trip statistics between the two. This would tend to prove out if longer commutes showed a closer result between the two as warmup time diminished as a factor of overall operating time. Is this along the lines of what you are saying?

Seems a fair trade for warmth, actually. I don't think any ALH drivers in MN would mind if their cars heated up quicker in January

 

[IndigoBlueWagon]

I don't drive my common rail car on a lot of short trips, but when I have in winter I'd see 38-39 MPG. The ALH in similar driving will get me 41/42. In summer they both get 43/44 in short trip driving only.

I don't know if the CR is less efficient during warm up, or less efficient overall when it's cold. BTW both cars have winter fronts on the which helps, especially in the ALH. The ALH was reluctant to get to full temp at all when it's below about 20 out, even on the highway, without the front. The CR will get to temperature, but FE is lower without the front.