Diesel engines are the proven sweethearts of the transportation industry. I’m sure you’re seeing more and more in your shop, given their increasing popularity among light- and mid-duty pickup truck owners. They’re basically for anyone who needs to carry and/or tow heavy loads. While a diesel engine tends to create its peak horsepower and torque at lower rpm ranges than a gasoline engine, diesels are commonly known for their ability to offer greater torque. If maintained properly, a diesel engine will typically offer a vastly superior lifespan as compared to a gas engine. And in the “old days,” diesel fuel cost less than gasoline. So when you add it all up, it’s no mystery why those who towed loved their diesels.
However, thanks to tightening emissions mandates, changes have been made to today’s diesel fuel, which offers less lubricating benefits for the fuel system and exhaust valves, and it carries a heftier price tag at the pumps due to the increased refining cost required to meet Environmental Protection Agency (EPA) rules.
Today, your customers who run light-duty diesel engines need to pay more attention to both the fuel and the oil that they use and to be aware of the need for specific additives/treatments in order to boost their vehicles’ performance, avoid drivability issues, increase their mileage and prevent premature injector wear.
Diesel fuel’s cetane rating is similar to the octane rating of gasoline. The cetane rating (CN) is a measurement of the combustion characteristics of diesel fuel. Since a diesel engine ignites its fuel through the use of compression (while a gas engine uses a spark to ignite the fuel), the cetane rating must be high enough to allow the fuel to ignite as the cylinders build compression.
The “knock” that is heard when a diesel fires is the result of the initial fuel igniting after an initial delay. Once the engine fires, the resulting fuel flow ignites more smoothly. A higher cetane rating shortens this initial ignition delay (because higher cetane rated fuel ignites more easily). Typical cetane ratings in diesel fuel sold in the U.S. carries a cetane rating in the 40 to 55 range.