Multi-grade oils, like a 10W-30, will have better low-temperature properties than mono-grade oils, such as an SAE 30. ?That?s because they contain a viscosity modifier,? says Gapinski. ?When these are present, they help flatten the response of an oil to temperature. The higher the viscosity index number, the less the fluid changes with temperature.?
For multi-grade oils, the number in front of the ?W? is a measure of pumping and cranking performance, with each step lower (15W, 10W, 5W, 0W) representing a 5° C (9° F) increase in low-temperature capability, explains Eric Olsen, lubricants technology, engine oils team, Chevron Global Lubricants.
?Generally, an SAE 15W-40 will have good pumpability down to -25° C (-13° F), while an SAE 5W-40 would extend the range down towards -35° C (-31° F),? he says. ?My choice of the word ?generally? is intentional, because the SAE viscosity system was developed using gasoline engines. So for diesels, [it] is correct as a relative ranking system rather than for absolute limits.?
Many truckers in warmer states use SAE 15W-40 year-round, Olsen continues. But in colder climates, some will change to SAE 10W-30 or SAE 5W-40 to help maintain operations as temperatures cool. ?For example, about the time of year footballs start flying, a trucker might notice slower cranking or a few more turns before the engine fires up in the morning,? he says.
?As snow begins to accumulate, it is vital to ensure you are using an oil that will stay liquid,? Olsen asserts. ?The alternative can be sudden engine death. This happens when an oil gels or becomes a semi-solid at low temperatures. If an engine were to start with such a gel in the pan, it would not be long before the oil pump would suck air, leaving the bearings dry to grind themselves apart.?
Use the right mix
Also make sure your coolant is at the proper ratio so it doesn?t freeze. The optimum ratio is 50% coolant and 50% water. Keep a refractometer in your shop to accurately identify the concentration. ?At that ratio, the freezing point is -34° F,? says Arcy. ?If you get a higher concentration of water, your coolant will freeze at a higher temperature.?
?If the expected ambient temperature is going to be below -34° F, you can adjust the freeze point by adding more antifreeze/coolant concentrate,? says Carmen Ulabarro, direct marketing manager, Chevron Global Lubricants. ?However, the maximum recommended amount of glycol should not exceed 60%, since adding too much antifreeze concentrate can actually reduce freeze protection.?
If you?re using a non-extended life coolant, check the inhibitors to ensure cooling system components will be protected. ?If your conventional coolant has been run for more than 250,000 miles, think about changing it out,? Ulabarro advises. ?Over time, the solids in the system can get too high and may create issues with plugging. Also, be sure to check all hoses and fittings and replace any worn hoses and tighten loose clamps. If temperatures are extreme ? below -60° F ? consider using a PG coolant vs. an EG-based coolant, because it has a lower freeze point.?
Beyond fluid selection
There are also certain tasks you can do at startup and shutdown to ensure your equipment will operate properly.
If you know it?s going to be extremely cold the next morning, park equipment indoors at the end of the day if you have that option. ?Try to keep it as warm as possible,? says Gapinski. ?There are also engine heaters that can give you a jump start.?
In addition, check the pour point of any fluids you?re using. (This information is available from product data sheets from the fluid marketer.) The pour point is the point at which the oil is incapable of being poured/stops flowing. ?It?s the responsibility of the customer to know the pour point,? says Gapinski. ?If the temperature is below that number, don?t use the equipment. To avoid damage and a lot of expense, it?s better to go home that day.?
Selecting the right fluids is even more critical if you don?t use a piece of equipment every day. ?If your equipment has sat unused for three or four days, you will want to select a fluid that flows easily so the equipment starts easily,? says Arcy. ?If you use the equipment every day, at startup, run the vehicle to the point where it?s hot.