AMSOIL 15W-40 Heavy-Duty Diesel & Marine Oil AME1GC | 3.78 L

AMSOIL 15W-40 Heavy-Duty Diesel & Marine Oil | AME1GC | 3.78 L

Overview

AMSOIL AME1GC is a synthetic SAE 15W-40 heavy-duty diesel and marine engine oil formulated for high-load, high-temperature diesel applications. Its 12 TBN detergent package helps neutralize acids from combustion and EGR blow-by, while the synthetic base resists heat-related breakdown and viscosity loss. It is rated for API CI-4+ and earlier diesel-oil specifications, making it a strong match for older marine diesel engines that benefit from high-detergent, soot-controlling formulations. Always verify the engine manufacturer’s required oil specification before selecting an oil.

Compatible Applications

• Marine diesel engines specifying SAE 15W-40 and API CI-4+ or earlier diesel-oil categories
• Heavy-duty commercial diesel engines
• Off-highway diesel equipment
• Older diesel engines with high soot and wear requirements
• High-load, high-temperature diesel applications
• Extended-drain capable applications where supported by the engine manufacturer and oil analysis

Important: For engines fitted with modern diesel particulate filters (DPF) or low-SAPS emissions systems, follow the engine manufacturer’s required oil specification — not viscosity alone — when selecting engine oil.

Performance Characteristics

• 12 TBN for acid neutralization from combustion and EGR blow-by
• Strong soot-dispersing capability — resists viscosity increase from soot loading
• Protection against cylinder-bore wear and polishing
• Controls varnish, sludge, and deposit formation
• Resists oil oxidation and thermal breakdown at high operating temperatures
• Reduced oil consumption in high-load service
• Improved cold-weather startup protection versus conventional heavy-duty oils

Size Options — Same Formulation

• AMSOIL AME1GC 15W-40 Heavy-Duty Diesel & Marine Oil — 946 mL / 1 Qt (AMEQTC)
• AME1GC — 3.78 L / 1 Gallon (this listing)
• AMETPC — 9.46 L (contact us for availability)
• AME55 — 208 L drum (contact us for availability)
• AME27 — 1041 L tote (contact us for availability)

Service Interval

Change engine oil according to the engine manufacturer’s specified interval or hours of operation. Extended drain intervals should only be used where supported by the engine manufacturer, oil-analysis results, or AMSOIL service guidance. Change the oil filter at every oil change as specified.

• Follow the engine manufacturer’s required change interval or hour-based service schedule
• Reduce interval in severe service, high-soot, or fuel-dilution conditions
• Follow annual lay-up or seasonal service requirements for marine engines
• Consider oil analysis to confirm extended-drain suitability for your application

Service Notes

• Replace the engine oil filter at every oil change
• Verify crankcase capacity before service — do not overfill
• Avoid mixing with unknown or contaminated oils
• Inspect for leaks after refill and check oil pressure at startup
• Recheck oil level after the engine has fully circulated the new oil
• Confirm the required API category and viscosity match your engine manufacturer’s specification before use

Related Products

• AMSOIL AMEQTC — 15W-40 Heavy-Duty Diesel & Marine Oil, 946 mL / 1 Qt
• AMSOIL Oil Filter ASF-25
• Volvo Penta VDS-4.5 15W-40 Diesel Engine Oil — 5 Gallon (23219264) (OEM alternative for Volvo Penta diesel applications)
• Yanmar 15W-40 Marine Engine Oil — 1 Gallon (OEM alternative for Yanmar diesel applications)

Technical FAQ

What engines is AME1GC designed for?

AME1GC is formulated for heavy-duty diesel and marine diesel engines that specify SAE 15W-40 viscosity and an API CI-4+ or earlier diesel-oil category. It is particularly well suited to older marine diesels, commercial engines, and high-load applications where strong soot control and high TBN are priorities.

Can I use AME1GC in a modern diesel with a DPF?

Not without verifying the engine manufacturer’s specific oil requirements. Modern DPF-equipped engines typically require low-SAPS oils meeting API CJ-4 or later specifications. Always match the oil to the engine manufacturer’s required specification, not just the viscosity.

What is TBN and why does it matter?

TBN (Total Base Number) measures an oil’s ability to neutralize acids produced during combustion. A 12 TBN is relatively high for a 15W-40 diesel oil, which makes AME1GC a strong choice for engines that generate significant combustion blow-by or run EGR systems that increase acid load on the oil.

What is the difference between AME1GC and AMEQTC?

Same formulation — same oil, same viscosity, same API rating. AME1GC is the 3.78 L / 1 gallon jug; AMEQTC is the 946 mL / 1 quart size. Choose the size that suits your service quantity and storage needs.

Can I extend my oil change interval with AME1GC?

Extended drain intervals are only recommended where supported by the engine manufacturer, oil-analysis results, or AMSOIL’s specific service guidance for your application. Do not extend drain intervals without confirming the engine manufacturer allows it and that oil condition supports it.

Which oil filter should I use with AME1GC?

Use the oil filter specified by your engine manufacturer. The AMSOIL ASF-25 oil filter is available in-store for compatible applications — confirm the correct filter for your specific engine before ordering.

Parts Desk Insights

Best use case: AME1GC is the right choice for older marine diesel engines — think Yanmar, Cummins, Detroit Diesel, or older Volvo Penta diesels — where the engine manual calls for 15W-40 and an API CI-4+ or earlier category. The high TBN and synthetic formulation make it a step up from conventional heavy-duty diesel oils in the same viscosity class, particularly for engines running extended hours between service, or in boats that see infrequent seasonal use where oil degradation matters. It’s also a cost-effective option for customers who want a premium synthetic at a lower price than OEM-branded lubricants.

Common customer questions: The most frequent issue is customers assuming any 15W-40 diesel oil will work in their engine, including modern DPF-equipped engines. Always confirm the engine’s required API category before completing the order — AME1GC is a CI-4+ oil, not a CJ-4 or CK-4 low-SAPS oil. The second common question is about drain intervals — customers ask if they can run it longer than the OEM interval. The answer is “only with oil analysis or explicit AMSOIL guidance for their application”, not simply because it’s synthetic. Also confirm the correct filter for their engine if they are ordering oil and filter together.