All About Fuel Types

When you’re filling up at the pump, you already know what type of fuel to use for your car. Whether that’s diesel, regular unleaded, or premium – but did you know there’s more diesel fuel types out there? Biodiesel, diesel exhaust fluid (DEF), ultra-low sulfur diesel – what does it all mean? We’re here to break down all of the alternative diesel fuel types for you.

Biodiesel is a form of alternative fuel derived from plants and animal fats that gets blended with petroleum diesel. This blend is shown as a percentage in the name – for example, 2% biodiesel. Biodiesel is more environmentally friendly and cost-effective than petroleum diesel by itself. It’s used primarily in light to heavy duty vehicles.

Diesel exhaust fluid (DEF) is not a type of fuel but a colorless liquid used in diesel engines to reduce emissions. It is stored separately from the fuel tank and needs refills, similar to fuel. It is composed of urea and water, and is injected into the exhaust stream to transform nitrogen dioxide and monoxide into harmless nitrogen and water.

Ultra-low sulfur diesel (ULSD) is a type of diesel fuel made with lower sulfur content. Usually, diesel vehicles that are model year 2007 or later require this fuel type. This fuel type was also created for lower emissions in mind – more specifically, sulfur oxide – as the max sulfur limit in fuel was previously 500, then decreased to 15 parts per million (ppm).

Regular, mid-grade, and super unleaded fuels differ by octane rating. A higher octane rating means higher engine performance and power. Most vehicles can run on standard petrol while others may require a higher octane fuel, such as premium or super, to run better and produce more power. Typically, the higher octane, the pricier it is due to the costlier process of producing the fuel type.

With fueling stations all across the U.S., Quarles can help keep your fleet running on schedule and give you the best premium diesel and fuel we have to offer. Unleaded gasoline is available at all of our locations, with off-road fuel, DEF, and biodiesel available at select locations. Find out more on our website at or give us a call at 877-444-3835.