HOT/COLD DURAMAX OPERATION
I recently bought a used 2007 GMC equipped with the Duramax, and I have a few questions concerning cold starting and turning off the engine. I live in northeastern Montana, so it can get pretty cold during the winter. I’ve been told that I should consider plugging in the engine block heater whenever the overnight low dips below +20 degrees F. So, my question is: how long should I let the engine warm up in those conditions before starting? Is engine warm-up as important during the summer months? Also, what is the appropriate cool down for the turbo before shutting the engine off? One mechanic says wait 5-7 minutes. Another says I can shut it off right away. I heard the turbo can bake the oil in its bearing assembly if not allowed to cool down properly. Please help a new diesel owner. Thank you for a great magazine!
Terry Tyler Circle, Montana
The light-duty diesel industry has done an excellent job producing engines that operate much like their gasoline equivalents in all temperatures. So, while Montana winters can stress any engine during a cold start, it’s actually pretty easy to live with a diesel engine in cold weather. I also live in Montana and have driven a dieselpowered pickup every winter since 1986.
At temperatures of +20 degrees F or below, I recommend using an electrical timer rated for a 15-amp load that you can use to switch on the engine block heater a couple of hours before you need to drive the truck. This is sufficient to produce normal and quick starts when the vehicle is parked in an unheated garage—even when the outside temperature dips well below zero. I would double the block heater time if the truck sits outside. It’s a waste of electricity and heater life to leave the engine block heater plugged in all of the time the truck sits (unless, perhaps, you live in Fairbanks).
As far as a recommended engine warm-up time after a cold start (summer or winter), I normally drive away soon after the engine has settled down and is running smoothly (15 seconds to a minute at most). A side benefit of using the block heater during the coldest days of the winter is that the truck’s cabin heat and defrost will begin as soon as the engine starts. Drive easy until you see the engine temperature gauge begin to climb past the 100-degree mark. Driving the truck will allow it to warm up much faster than it would if allowed to sit and idle. In fact, it might never reach operating temperature while idling in cold temperatures. All of this applies to summer starts as well.
I’ve used a diesel-rated synthetic in my diesel pickup through most of the winters here in Montana. In a Duramax, the recommended oil drain interval is 7500 miles, so the more costly synthetic isn’t a significant factor in overall maintenance costs. The real benefit of synthetic is its cold weather performance. It allows the engine to start much easier.
GM offers a winter front accessory for diesel pickups wherever new trucks are sold in the cold areas of the country. A winter front is usually a black vinyl snap-on or clip-on cover for the grille of the truck. This reduces the amount of air entering and passing through the radiator area, which allows the engine to run warmer. Think of it like a windbreaker for your truck. Obviously, this should be removed if you’re towing or if you discover the engine runs too warm. A quick internet search should produce a variety of grille covers to choose from that were designed specifically for your truck. Look for one that is easy to install/remove and doesn’t require modifying the truck (drilling holes, etc).
Finally, regarding your turbo shut-down question: modern diesel engines and turbochargers don’t require much in the way of cool-down before shutting off the engine. Turbocharger temperature usually drops to a safe level by the time you’ve pulled off the highway and have come to a stop. The only exception would be if you’re towing a heavy trailer up a long, steep grade during the summer months and then pull over at the top of the hill. The oil in the turbo could cook (or coke) if the engine is shut off with the turbo at a high temperature. In this situation, I’d let the engine idle for a few minutes before switching off the key. Good luck.