Royal Purple Duralec Super 5W-40 CK-4 Diesel Engine Oil — 1 Gallon, Emissions‑Compliant & DPF/SCR Safe

Royal Purple Duralec Super 5W-40 CK-4 is a synthetic diesel engine oil formulated for modern emissions systems that helps protect components, improve fuel performance, and extend drain intervals.

Designed for diesel engines that must use emissions-compliant lubricants, this 1-gallon Royal Purple Duralec Super 5W-40 (SKU 83540) meets API CK-4 performance requirements for North American and European ultra-low sulfur diesel. The formulation balances high-temperature stability with low-temperature pumpability to limit startup wear, support exhaust aftertreatment devices like DPFs and SCR systems, and maintain protection across a wide range of operating conditions.

How does this oil protect modern diesel emissions equipment?

Duralec Super is engineered to be compatible with diesel particulate filters, selective catalytic reduction, EGR and catalytic converters by controlling deposits and managing ash levels. Its base oils and additive package are selected to support emissions systems while providing robust protection for internal components.

• Formulated to preserve DPF and SCR function by controlling soot and deposits.
• API CK-4 licensing for compatibility with modern diesel engines.
• Balanced additive chemistry to reduce ash-related fouling of aftertreatment devices.

What performance can I expect in hot and cold conditions?

This 5W-40 grade offers cold-start flow performance at lower temperatures while retaining shear stability and film strength at high operating temperatures. The result is reduced wear during startup and dependable protection under sustained load and heat.

• 5W-40 viscosity for easier cold pumping and reliable high-temp film strength.
• High-temperature breakdown resistance to protect bearings and pistons under load.
• Low-temperature pumpability to reduce startup wear in cooler climates.

How does it affect maintenance intervals and fuel economy?

Royal Purple formulates Duralec Super to help extend drain intervals where manufacturer recommendations and service conditions allow, by resisting oxidation and controlling contaminants. The oil’s friction modifiers and stable viscosity profile can also contribute to improved fuel efficiency compared with less advanced formulations.

• Oxidation resistance helps maintain oil performance over longer drains.
• Friction control elements support reduced internal friction and improved fuel performance.
• Corrosion inhibitors protect metal surfaces during extended service periods.

Which engines and applications is this oil appropriate for?

Duralec Super 5W-40 CK-4 is formulated for modern heavy-duty diesel engines requiring CK-4 oils and for equipment fitted with emissions control devices. It is suited for on-highway trucks, vocational equipment, and any diesel application where API CK-4 and a 5W-40 viscosity are specified.

• Meets API CK-4 for 2007–2010 emissions-era diesel engines and newer where CK-4 is acceptable.
• Works with ultra-low sulfur diesel fuels common in North America and Europe.
• Appropriate for engines with DPF, EGR, SCR, and catalytic converters.

Who is this for: Royal Purple Duralec Super 5W-40 CK-4 is targeted at fleet managers, owner-operators, and equipment owners who need an emissions-compliant synthetic diesel oil that balances protection, drain-life potential, and fuel performance. Choose this 1-gallon pack when your engine manual calls for a CK-4 oil in the 5W-40 viscosity and you want a premium formulation designed for modern diesel exhaust aftertreatment systems.

Features

• Greater wear protection
• Improves fuel economy
• Superior corrosion protection
• API-licensed CK-4 diesel motor oil