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Driving A Diesel In The Winter

Q. Dear Vincent, Hi, your article about diesel engines is very informative! I just recently bought a 1984 Mercedes Benz 190D with a 2.2 liter diesel engine. It has an automatic transmission and has 160,000 miles. I live here in Wisconsin. I'm familiar how diesel engines work, but my knowledge about diesel engines stops there. Will my diesel engine run in the winter?

Driving A Diesel In The Winter

They say diesel engine gels in the cold, how can I prevent this? Is there a portable engine heater? I don't have a garage to plug a heater. Please inform me about the tips and tricks in diesel engines.


A. I have a 1983 Mercedes Benz 300D turbo diesel and I live in Minnesota so I know what you mean. There is no reason a diesel will not run in the winter. I use mine all winter with no problems.

First off, diesel fuel is very high in paraffin, basically, candle wax. This paraffin turns solid the colder it gets. You can get diesel fuel anti-gel at any auto parts store. I use the NAPA brand anti-gel since it seems to work for me.

Related to this is the fuel filter. I have learned through hard experience it is best to replace both fuel filters before the weather turns too cold. A dirty fuel filter is more prone to collecting paraffin crystals and cutting off the fuel.

Never use kerosene or gasoline to prevent the fuel from gelling. It lowers the flash point of the diesel fuel and increases the risk of engine damage.

Again, before it gets too cold, have the glow plugs tested. The pencil element glow plugs consist of a housing, with a heater bar, and external threads. The electrical connection is maintained by a non-releasable brass nut. The heating element consists of a heating and control winding connected in series.

When the glow plug system is turned on, a current of approximately 30 amps will flow per glow plug. The winding increases its resistance with increasing temperature and limits the current to approximately 8 to 15 amps. This will protect the glow plug against overload.

The glow plugs are designed for a voltage of 11.5 volts and are operated as a parallel circuit. After a glow time of 9 seconds, a heater bar temperature of approximately 1,500°F will be attained.

The glow plugs heat the cylinders so the diesel fuel will ignite. If one or two glow plugs are bad, the engine will be difficult, if not impossible, to start.

An engine heater is not required, but it is a huge help in cold weather starting. Especially when the temperatures get to 20°, 30° and 40° below zero.

I have a block heater in mine and I run the cord from an outside outlet on my deck to plug in the heaters. I actually have two, one in the block and a magnetic one on the outside of my oil pan, below the oil level. Motor oil gets pretty thick at those temperatures also. I'm sure there is a way to get power to a block heater from your house. Even if you have an electrician install an outdoor outlet, it will be well worth it.

Make sure the battery is good also. Diesel batteries are much bigger than batteries for gas engines due to the higher compression ratios. I replace my battery every three years weather it needs it or not.

Speaking of motor oils. I use a 0W40 in the winter and change it back to a 20W50 in the summer. It makes a big difference in winter starting. An oil and filter change before winter hits is always a good idea for any vehicle.

These tips will apply to any diesel engine, not just a Mercedes diesel. If you follow these suggestions you shouldn't have any problem in starting and driving your diesel in the winter.

Additional Information provided courtesy of AllDATA

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