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Diesel Engine Oil Guide

Your choice of engine oil is important, especially when it comes to diesel vehicles. The standards that apply to gas engines may not apply to your diesel, and nowhere is this more obvious than with the engine oil. The following can help you better understand the oil needs of your vehicle.

Does the type of diesel oil matter?

Diesel oil is divided into two main types. Those marketed for off-road vehicles may be labeled as CK-4 or high viscosity diesel oil. This oil performs well at the high temperatures that occur in off-road engines, but it doesn't provide the same level of gas efficiency found in the other type of oil. Highway-use diesel oil is labeled as FK-4 or as low viscosity oil. These oils help lower emissions while increasing fuel economy, a must for vehicles on highways that tend to travel further distances than an off-road vehicle. In a pinch, you can use a CK-4 oil in a highway vehicle, but FA-4 oil should never be used in an offroad vehicle.

Is conventional or synthetic oil better?

Conventional oil is more likely to contain particulates, which can damage your engine over time. Synthetic oils do not contain these impurities, which leads to better engine performance and lowers the need for certain types of repairs. The price of synthetic oil is sometimes greater than that of conventional, but the extended life of a max duty synthetic diesel oil and fewer repairs over the life of the vehicle can make the relatively small investment in synthetic a small price to pay.

Can gas engine oil be used in a diesel engine, or vice versa?

Diesel oil mainly differs from gas engine oils in the additives. Since many diesel vehicles operate with at higher horsepower, the oil contains extra detergents to prevent impurities from forming and harming engines. Diesel oils are also available in a greater range of viscosity, compared to gas engine oils, so that they can serve the needs of the various vehicles and equipment types that run on diesel. In some cases, you can use diesel engine oil in your gas engine, as long as the specification matches that of your gas engine. For example, if your owner's manual recommends a 15W-40 gas engine oil, you can substitute a max duty diesel oil 15W-40 without concern. On the other hand, gas engine oils do not have the additives and anti-foaming agents necessary for diesel engines, so you can't use gas engine oil in a diesel vehicle.

Contact a diesel engine service for more help.