Diesels In Cold Weather: Think Before You Buy

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2012 Volkswagen Passat TDI Six-Month Road Test

2012 Volkswagen Passat TDI Six-Month Road Test

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Chances are, somebody reading this lives in a fairly cold climate. You also probably want to save money on fuel, and may have considered diesel.

But have you considered the effect that cold weather might have on a diesel vehicle? One tale from The Car Guide shows why diesel vehicles may not be your first choice in very cold climates.

Testing Mercedes-Benz Sprinter diesel cargo vans, a group of reviewers encountered several difficulties due to the excessive cold of the Alaskan Arctic Circle--with temperatures lower than -40F on several occasions.

Testing only goes so far...

There was a time when passenger cars were designed, built, maybe driven up and down the nearest road a few times, and then sold to the public.

If you bought such a car and then spent any time driving it in ultra hot or cold conditions, you'd quickly discover its foibles--it wouldn't start, the windows would fall out or shatter, it would melt or dissolve--that sort of stuff.

Nowadays things are different, and pre-production testing is incredibly rigorous. Among these tests, cars are often driven in Arctic conditions to ensure they'll work even in the coldest of climates.

Diesels and extremely cold weather

Fluids, and particularly diesel itself, behave differently as the temperature drops.

Diesel's viscosity increases at lower temperatures, known as "gelling" or "waxing", eventually to a point where it cannot be pumped and the engine dies--or is unable to start in the first place.

This manifested itself as a group of the Sprinter vans not starting on the second morning of the test, despite being equipped with auxiliary heaters for the engine, BlueTEC emissions system and the fuel filter.

Most of the vans were eventually re-started, but drivers still experienced occasional running problems and noises from the vehicles, which Mercedes had tested to an extreme--but apparently insufficient--minus 30 fahrenheit.


As the reviewer points out in his third report, it's hardly Mercedes' fault that the vans had issues--the huge majority will be sold in warmer climates.

Auxiliary heaters are a popular--and necessary--way of keeping both diesel and gasoline vehicles warm in extremely cold conditions, and many areas in Alaska, Canada, Scandanavian countries and more will provide plugs at parking spaces for hooking up block heaters.

This keeps the engine warm and lubricants flowing, so engines are easier to re-start after a night out in the cold. Some cars, like the 2014 Chevy Cruze Diesel, actually offer this as an option.

As the Mercedes test proved though, they can only do so much.

A more extreme preventative measure is to leave the engine idling. It's a technique used by truckers up in the Arctic circle, and it isn't the greenest of methods, but in extreme cases it may be the best method.

Colder regions also sell special diesel mixes that resist diesel's "gelling" tendencies. It's worth remembering this if you're ever driving a diesel to a colder region--try not to arrive there with a full tank of warmer-weather diesel, unable to fill up with a more suitable mix.

All vehicles will suffer to some degree in extremes of cold. Electric cars in particular can suffer--so we've compiled a handy guide to help you maximize your driving range when the mercury drops.

So it's worth bearing in mind: Some fuels are simply better suited to the conditions than others.


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Comments (13)
  1. In Finland for example they sell "winter diesel" and "summer diesel" depending on the season to mitigate the issue mentioned in the article.

  2. Perhaps the title should have been "Diesels in Extreme Arctic Temperatures: Think Before You Buy." If you're talking "cold weather," plenty of people in Maine own diesel pickup trucks, including a friend of mine who just bought an enormous Ford F350. Plug-in block heaters are pretty much standard, not just something "actually offered as an option."

  3. I'm living in Wyoming with my TDI and have one glow plug out - but it'll still start down to 10 degrees or so. With the glow plug good it was fine at minus 10. All without a block heater! Don't let cold weather deter you from getting a diesel - I love mine

  4. Are you really living with your TDI? :-)

  5. The title of this article is misleading. The conditions depicted are extreme cold, not just cold.

  6. All the more reason to read the rest of the article, rather than stopping after the title...

  7. I have a Passat TDI. These modern injection systems work wonders to compensate and aid starting in very cold weather. My Passat WILL start in 0 degree weather without a block heater! Yes, I was somewhat surprised that it did, the first time I was in that situation. -- Amazing compared to the older diesels, with which you needed a block heater at those temperatures.

  8. As the temperature drops the Paraffin wax in Diesel will plug your fuel filter way before you get to the lower temperature that jells the fuel to a point it will not flow through the fuel lines. You can put additives in the fuel to keep the wax crystals from combining. Then the individual wax crystals will be small enough that they will pass through the filter media.

  9. I live in North Dakota and don't have a plug in heater for my TDI. It gets #1 diesel from December through mid March. Oil is always Mobil Delvac 5-40. No problems with starting, though the glow plugs do stay on for a long time at -25F.

  10. Scaremongering, Mr. Ingram? Why?

    All that is needed is to pour some gasoline into the tank. Standard practice when it gets below -30 C.

    I live in a fairly cold climate (last Winter, it was down to -20 C). My diesel engine started every time, "as soon as it saw the key", as the saying goes.

  11. @Annatar: I'm not sure where you live, but I suspect that the maker of your diesel car would have a good case for denying you any warranty claims on the engine or fueling system due to misfueling.

    Pouring "some gasoline into the tank" is a fairly clear contravention of the fueling for a diesel car. At least for modern (2009-on) diesel vehicles in the U.S. market.

    What does your Owner's Manual say about putting non-diesel fuel into your car?

  12. And just what do you think the diesel fuel additive against gelling is, Mr. Voelcker?

  13. my 2012 passat is good to -20 C then i have t plug it in and it starts no problem

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