The Complete Guide to AMSOIL Marine Lubricants
Marine engines live a brutal life — sustained wide-open-throttle operation, long idle periods between trips, humidity, salt spray, and ethanol-blend pump gas that attacks the fuel system. AMSOIL builds a full line of NMMA FC-W and TC-W3 certified synthetic marine lubricants engineered for exactly that duty: 4-stroke outboards from Mercury, Yamaha, Suzuki, Honda, and Tohatsu; direct-injection 2-stroke outboards (Mercury OptiMax, Yamaha HPDI, Evinrude E-TEC, Tohatsu TLDI); MerCruiser and Volvo Penta sterndrives; and Cummins Marine, Yanmar, and Volvo Penta D-series inboard diesels.
4-Stroke Marine Engine Oil — Pick the Right Viscosity
AMSOIL 10W-30 100% Synthetic Marine (WCTQT-EA) covers most modern 4-stroke outboards in the 25–250 hp range — Mercury Verado, Yamaha F-series, Suzuki DF, Honda BF, and Tohatsu MFS. AMSOIL 10W-40 100% Synthetic Marine (WCFQT-EA) is the right call for higher-output 4-strokes (Mercury Pro XS 4S, Yamaha SHO/VMAX SHO) and warm-water service — perfect for Florida and Gulf Coast boats. AMSOIL 25W-40 Synthetic-Blend Marine (WCMQT-EA) is engineered for MerCruiser, Volvo Penta, Crusader, Indmar, and PCM gas sterndrives and inboards. All three carry NMMA FC-W Catalyst Compatible certification.
2-Stroke Outboard Oil
AMSOIL HP Marine 2-Stroke (HPMQT-EA) is the premium NMMA TC-W3 oil for direct-injection 2-stroke outboards — Mercury OptiMax, Yamaha HPDI, Evinrude E-TEC and FICHT, Tohatsu TLDI. It controls ring sticking, exhaust port deposits, and piston scuffing under sustained marine load. For traditional oil-injected outboards, AMSOIL Synthetic 2-Stroke Injector Oil (AIOQT-EA) delivers true synthetic protection at a value price point. For premix-only kickers and small outboards, AMSOIL 100:1 Pre-Mix (ATOBC-EA) mixes at 100 parts gas to 1 part oil for cleaner combustion and reduced smoke.
Lower Unit Gear Lube
AMSOIL 75W-90 100% Synthetic Marine Gear Lube (AGMPK-EA) is a full-synthetic GL-5 marine gear oil engineered for outboard and sterndrive lower units. It resists water emulsion (critical when a seal weeps slightly), prevents foaming, and protects the gears under full-throttle saltwater service. The pump-pack bottle eliminates funnels and spillage during routine service.
Marine Diesel
AMSOIL 15W-40 Heavy-Duty Diesel and Marine Oil (AMEQT-EA) is API CK-4 / CJ-4 certified for inboard marine diesels — Cummins Marine QSB / QSC / QSL, Yanmar marine diesel, Volvo Penta D-series, and other commercial and recreational marine diesel applications. Excellent soot dispersancy, high-temperature oxidation resistance, and protection through extended service intervals.
Cooling, Grease, Filters & Storage
Round out a full marine service with AMSOIL Powersports Antifreeze (PSAFQT-EA) for closed-cooling systems, Synthetic Water-Resistant Grease (GWRCR-EA) for trailer wheel bearings and chassis points, AMSOIL EaO/EaOM/EaOMC and WIX oil filters matched to the engine, and storage products: Quickshot (AQSCN-EA) for between-trip ethanol cleanup, Gasoline Stabilizer (ASTCN-EA) for off-season fuel preservation, and Engine Fogging Oil (FOGSC-EA) for laid-up cylinder protection — all critical for boats that sit through hot, humid Florida summers.
Independent AMSOIL Dealer — Florida and Nationwide
1stSynthetic.com is run by Eric Riley, an Independent AMSOIL Dealer based in Dade City, Florida — serving boat owners across Tampa Bay, Lakeland, Wesley Chapel, Zephyrhills, Brooksville, Brandon, Sarasota, Crystal River, Homosassa, Cedar Key, and the entire Gulf Coast, plus lake, river, and coastal customers throughout the United States. Order online and ship direct from the AMSOIL distribution center, or join the Preferred Customer program to save 25% on every marine order, every time.
