Sierra Oil Filter 18-7878-1, Replaces 3517857, Fits AD31A, AQAD30A, AQAD31A Marine Engines

The Sierra 18-7878-1 is an oil filter engineered for marine diesel engines, designed to trap contaminants circulating in the lubrication system and keep engine oil clean between service intervals. It is built as a direct replacement for OEM part number 3517857 on AD31A, AD31L-A, AD31P-A, AD31D, AD31X, AQAD30A, and AQAD31A engine variants, giving boat owners and service techs a reliable option for scheduled maintenance without hunting down the original equipment part.

For these engines, the recommended lubrication is 15W-40 oil meeting VDS-2 or VDS-3 specifications, or API CI-4 or higher, with an engine oil capacity of 8.5 liters (9.0 quarts). Using the correct oil grade alongside the 18-7878-1 filter helps protect internal engine components from wear during normal operating cycles. The filter is sold under Sierra part number 18-7878-1 and weighs 0.99 pounds.

This filter is intended for routine replacement during oil changes and general engine maintenance on the listed engine models. Confirm your engine model designation against the fitment list below before ordering, since engine variants in this family use different filter part numbers.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7878-1
• Replaces (OEM): 3517857
• Fits Engines: AD31A / L-A / P-A / D / X, AQAD30A, AQAD31A
• Recommended Engine Oil: 15W-40, VDS-2 or VDS-3 / API CI-4 or higher
• Engine Oil Capacity: 8.5L / 9.0 Qt
• Weight: 0.99 pounds
• UPC: 808282241490

Fitment

• AD31A / L-A / P-A / D / X
• AQAD30A
• AQAD31A

Replaces (OEM)

• 3517857

Frequently Asked Questions

What engines does the Sierra 18-7878-1 oil filter fit? The 18-7878-1 fits AD31A / L-A / P-A / D / X, AQAD30A, and AQAD31A engine variants. Check your engine's exact model designation before ordering since related engines in this family use different filter part numbers.

Is the Sierra 18-7878-1 a direct replacement for OEM part 3517857? Yes, the 18-7878-1 replaces OEM number 3517857 on the listed AD31A, AQAD30A, and AQAD31A engines.

How much does the 18-7878-1 oil filter weigh? It weighs 0.99 pounds.

What oil should I use with this filter? For engines using the 18-7878-1 filter, 15W-40 oil meeting VDS-2 or VDS-3, or API CI-4 or higher, is recommended.

What is the engine oil capacity for engines that use this filter? The AD31A, AQAD30A, and AQAD31A engines that take the 18-7878-1 filter hold 8.5 liters (9.0 quarts) of oil.

Does the AD31 engine family use more than one filter part number? Yes, within the AD31A / L-A / P-A / D / X, AQAD30A, and AQAD31A group the correct filter is 18-7878-1, while other related engines in the wider lineup use different Sierra filter numbers, so confirming your specific engine model before ordering is important.

What is the UPC for the Sierra 18-7878-1 oil filter? The UPC for this Sierra oil filter is 808282241490.

When should the 18-7878-1 filter be replaced? This oil filter is intended for replacement at each scheduled oil change on AD31A, AQAD30A, and AQAD31A engines to keep circulating oil free of contaminants.

Is the 18-7878-1 filter genuine Sierra or aftermarket? The 18-7878-1 is manufactured and sold under the Sierra brand as a replacement part for OEM number 3517857.

Will the 18-7878-1 filter fit AQAD30A engines specifically? Yes, AQAD30A is one of the engine variants that uses the Sierra 18-7878-1 filter, along with AQAD31A and the AD31A / L-A / P-A / D / X group.