Cummins Onan SAE 15W-40 Engine Oil — 2 x 1-Quart Bottles, Heavy-Duty Generator & Diesel Protection

Cummins 3265336 Onan SAE 15W-40 is a heavy-duty engine oil sold as two 1-quart bottles formulated for reliable lubrication of Onan and compatible diesel and gasoline generator engines.

Whether you're servicing a standby generator, RV power system, or commercial equipment, choosing the correct viscosity and formulation matters. This Cummins-labeled SAE 15W-40 oil is supplied in two convenient one-quart containers, making it easy to carry spares for on-site top-ups or oil changes. The product is intended for engines that specify 15W-40 viscosity and meets common performance standards for generator sets and small diesel motors.

Why choose 15W-40 for my generator or diesel engine?

SAE 15W-40 is a common multi-grade oil that balances cold-start flow with high-temperature protection. It helps maintain film strength under load and supports consistent oil pressure during extended operation. Use it when manufacturer guidance or engine manuals list 15W-40 as the recommended viscosity.

• Good cold-cranking performance for moderate climates
• Stable viscosity at high operating temperatures
• Suitable for many diesel and some gasoline generator engines

How do I use these one-quart bottles during maintenance?

The two-quart pack gives immediate capacity for top-offs or partial oil changes without needing to open a larger container. For complete changes, check your engine's total oil capacity and combine bottles as needed. Always use clean funnels and follow the equipment's recommended drain and fill procedures.

• Carry one bottle for field top-ups and one for a full change backup
• Store upright and replace caps after use to prevent contamination
• Dispose of used oil according to local recycling regulations

Which engines and specs is this oil compatible with?

Cummins-branded Onan SAE 15W-40 is intended for Onan generator sets and other engines that call for 15W-40 viscosity and comparable performance levels. Verify compatibility by checking your engine manual for API, ACEA, or equipment maker requirements before use. When in doubt, consult Cummins or an authorized service center.

• Engine types: Onan generator sets, many small diesel motors
• Check API/ACEA and equipment-specific specifications first
• Not all modern low-emission engines accept all 15W-40 blends

What storage and handling best practices should I follow?

Keep bottles sealed and stored in a cool, dry place away from direct sunlight and extreme temperatures. Prevent contamination by using clean dispensing tools and avoiding mixing with other oil grades or additives unless specified. Long-term storage is fine if containers remain unopened and intact.

• Store between freezing and moderate temperatures to preserve viscosity
• Label opened bottles with date and avoid prolonged exposure to air
• Recycle empty containers per local environmental rules

Who is this for: This two-quart pack is aimed at technicians, RV owners, fleet operators, and homeowners who maintain Onan generators or engines that require SAE 15W-40. It’s practical for on-the-road top-ups, scheduled maintenance, or keeping a spare at the workshop. Always confirm oil specifications with your engine manual and Cummins guidance before use.