skip to content
Driving Line Mark Logo

‘Tis the Season…7 Ways to Prep Your Diesel for Winter

Here comes the cool down… Freezing temperatures are gradually inching into the Midwest and northeast—and the mountains out West have already seen snow. Is your diesel ready for winter? Now’s the time to check the health of your batteries, ensure your block heater is operating correctly and stock up on your favorite fuel additive. And trust us, if you were thinking about buying new tires soon, there is no time like the present to throw some fresh tread on each corner.

While countless measures can be taken to ready a diesel vehicle for winter weather, we’ve narrowed it down to the top seven here. We can’t stress this to diesel owners enough: be proactive when it comes to preparing your work horse(s) for the cold. If you treat them right, they will always take care of you. Follow this basic checklist and your oil burner will be sure to survive Old Man Winter’s wrath.

1. Test Your Batteries

It’s not a coincidence that this one is first on our list. Dead batteries are the most common reason diesel owners are left stranded in the winter. Unbeknownst to many, a long, hot summer does more to damage our batteries than any other season. This is because fluid evaporation and corrosion is accelerated during warmer temperatures. Then, without us noticing our battery’s cold cranking amps have been reduced, we end up with an engine than turns over slower (warning sign) or one that starts fine one day, but is dead in the water the next.


The easiest way to check the health of your batteries is with a multimeter. Simply adjust your multimeter to any voltage setting higher than 15 volts, connect it to the battery leads and look for a reading of at least 12.6 volts. Then, with a helping hand, make sure voltage doesn’t dip below 10 volts while cranking the engine over. If either of those readings is low, you likely have a weak and/or dying battery. With the engine idling, voltage should check in between 13.7 and 14.7 volts. If possible, and because one good battery can mask the dying symptoms of the second battery on a diesel, pull your batteries and have them load tested at your local parts house. If your battery(s) fail any of the above test procedures, don’t chance it. Start with fresh units.

2. Test Your Block Heater

For trucks that live outdoors, a block heater can make or break them in cold weather. First and foremost, if your truck didn’t come from the dealer with a block heater and you live in a northerly climate, get one installed ASAP. If you do have one, it pays to inspect its functionality each year, before the weather goes south. Like an on/off switch, block heaters either function or they don’t—there is no in between. To test yours, simply attach the leads of your multimeter to the block heater plug’s prongs and set the multimeter to read ohms. Anything between 9 and 25 ohms indicates a working block heater. Less than 9 ohms and you may have a bad cord.


Block heaters are so effective they can even help fire up a truck that’s suffering from a few bad glow plugs, glow plug controller, or relay. In our experience (with a 7.3L Power Stroke), coolant and oil temp will increase roughly 10-12 degrees per hour while plugged in, with 130 degrees seeming to be the top-out temperature. There is a huge difference between trying to crank over an engine at zero degrees and one with 100 degrees of heat in it (think about how quickly your truck re-starts after being brought up to operating temp). One last word of block heater advice: don’t leave it plugged in 24/7. It’s best to have it connected to an outdoor timer that kicks on a few hours before you plan to start the truck.

3. Test Your Glow Plugs (if applicable)

Cummins owners need not heed the advice listed in this one (you guys don’t have glow plugs). For Power Stroke and Duramax fans, it’s hard not to notice the effects of having a bad glow plug or two in frigid conditions. Duramax and 7.3L Power Stroke mills in particular are notorious for eating glow plugs. Luckily, GM owners will be tipped off via a check engine light as to when a glow plug fails, as well as exactly which cylinder it is. On top of that, the glow plugs are located externally on the Duramax (near the exhaust manifolds), which makes replacing them a tad easier.


In the 7.3L Power Stroke’s case, the glow plugs are located under the valve covers—and these older trucks don’t necessarily throw a CEL when one decides to stop functioning. When diagnosing a glow-plug-related issue, it’s best to break out the test light and first check the glow plug relay’s functionality (they’re known to corrode, internally). If the relay checks out, unplug the under valve cover harness (UVCH) plugs, have a helping hand turn the ignition on and test the outsides of the connectors, followed by the insides of the connectors. If the test light doesn’t illuminate during the ladder test, you’ll be making a trip under the valve covers for further diagnosis.

4. Run a Lighter Weight Engine Oil

Prolonged sitting in freezing and sub-zero temps not only has the potential of gelling up the fuel in your truck (more on that in a minute), but it can also transform heavier weight engine oils into molasses. Upon initial startup during an average spring, summer or fall day, your engine sees oil pressure almost instantly. On colder days, oil pressure is a hair slower to build, but is still pretty quick. In arctic-like temps, the cold flow characteristics of most 15-weight engine oils are compromised, considerably. If you’re waiting 15-to-30 seconds before you see oil pressure, that’s a substantial amount of time for the bottom end of your engine to go without proper lubrication.


In particular, it’s extremely beneficial when 6.0L Power Stroke owners switch to a lighter weight oil. This is because the 6.0L’s HEUI injection system relies on engine oil to activate the fuel injectors—and thick, syrup-like oil doesn’t flow very well through the tiny passageways within the injectors. A 5-weight oil works wonders on these engines (as does a 0-weight) and helps solve a lot of its cold-start issues.

5. Use a Reputable Fuel Additive

Although refiners do a fairly adequate job lowering the cloud point of the fuel we buy at the pump, it can still gel up in conditions where temperatures dip below 20 degrees (F). To ensure the diesel in your tank continues to resist gelling, we recommend running a winter-specific fuel additive or at least an all-season blend. The chemical makeup of winter-use additives makes fuel more resistant to clouding up and crystalizing, disperses water without the aid of alcohol (alcohol is hard on injection system components) and offers a bump in cetane (i.e. energy).


Yours truly has always preferred the Stanadyne line of additives (a pint of its all-season performance blend is shown above). The way we see it, a company that builds injection pumps and injectors probably knows which additive is best to keep those components alive. If Bosch or Denso ever offer an additive, that too would have instant credibility in our opinion. For those of you living in the upper Midwest, northeast or Canada, add winter-blend fuel additive at every fill up.

6. Keep a Spare Fuel Filter in the Truck

In addition to starting with a fresh fuel filter(s) before winter hits, always keep a spare in the cab. The fuel filter location is the most common point for gel-ups, especially on aftermarket fuel systems mounted along the frame rail and not under the hood on the engine. It’s much easier for the minimal amount of fuel present in the filter to freeze overnight than the fuel in the tank.


For added insurance, we would also advise keeping a small amount of emergency fuel treatment on hand as well. Products such as Amsoil’s Diesel Recovery and Power Service’s Diesel 911 are designed specifically to dissolve gelled fuel and get you back on the road. However, emergency treatment fuel additives shouldn’t be used on a regular basis due to their harsh chemical makeup.

7. Buy New Tires NOW!

While the first six winter-prep tips are geared toward getting your engine started and operating safely in the cold, this one is paramount in getting you from point A to B. Trust us, if you’re ever going to need better traction, chances are it’ll be during the winter months. Don’t put off buying new tires.


For snow-covered highways and roads, choose an all terrain or light duty mud tire over an aggressive tread pattern. While large void mud tires work great off-road and in mud, their voids actually put less surface area in contact with the road, which can mean reduced traction. The Nitto Ridge Grappler, Terra Grappler G2 and original Terra Grappler are all great enablers for effective traversal of snow.

Return to beginning of article

Recommended For You

Loading ...