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AMSOIL'S Original Premium Protection 10W40

SAE 10W-40 Synthetic Premium Protection Motor Oil (AMO)
This was the original product Al Amatuzio first formulated in 1972 but has continuously been advanced with the best additives available for your classic or high performance vehicle.

"Most Versatile 10W40 Motor Oil on the Market"

Formulated for use in both gasoline and diesel engines. Offers multi-functionality and excellent wear protection. Ideal for applications where the extra protection of a higher viscosity oil is desired. Excellent for motor homes and older vehicles, as well as most types of modern equipment. Also compatible for use in motorcycles.

For other AMSOIL oils and viscosities containing the high anti-wear ZDDP amounts please see chart at bottom of page.

The only fully fortified synthetic oil for vintage cars with flat tappets.

Heavily fortified with zinc/phosphorus anti-wear additives for maximum protection.

Provides extra anti-wear protection required by engines with flat tappets and high tension valve springs.

Ideal for high mileage vehicles


Applications include street rods, cars, trucks, motorcycles, RVs, marine, tractors, heavy equipment and other applications where this oil is appropriate. Yes - this product is also our lower cost version of the Advanced Motorcycle Oil.

Printable AMSOIL Specsheet PDF for more detail on this 10W40 Product

You can also order in our new AMSOIL Online Store

See the special AMSOIL service bulletin on all AMSOIL high Zinc products.

  • API SL, SJ, SH... (Gasoline)
  • API CI-4+, CH-4, CF (Diesel)
  • JASO MA, ISO-L-EMA (Wet Clutch)


AMSOIL Synthetic 10W-40 Premium Protection Motor Oil is specially formulated to provide superior protection and performance in a wide variety of demanding applications. By incorporating high quality synthetic base stocks and additives, AMSOIL Premium Protection Oil exceeds the needs of large and small gasoline or diesel engines in cars, motorcycles, trucks, motor homes, maintenance equipment, heavy equipment, street rods and marine applications. AMSOIL Premium Protection Oil resists oxidation, neutralizes acids, inhibits corrosion, reduces wear and protects against deposits. It is ideal for high mileage vehicles and high-stress vehicles subject to hot temperatures, heavy hauling, trailer pulling or off road use. AMSOIL Synthetic 10W-40 Premium Protection Motor Oil provides flexibility and performance beyond conventional oils for convenience and trouble free operation.

AMSOIL, the leader in automotive synthetic lubrication, produced the world’s first API qualified synthetic motor oil in 1972. Trust the extensive experience of AMSOIL The First in Synthetics® to do the best job protecting your engine.

Provides Superior Wear Protection
AMSOIL Synthetic 10W-40 Premium Protection Motor Oil is a high viscosity oil engineered to protect against metal-to-metal contact. It resists viscosity shear and is formulated with a heavy treatment of anti-wear additives for excellent protection of gears, bearings, cam lobes and other high-pressure components in engines and transmissions. AMSOIL Premium Protection Synthetic Motor Oil helps extend engine life.

Exceeds the Requirements of Wet Clutch Transmissions
AMSOIL Premium Protection Synthetic Motor Oil contains no friction modifiers, making it ideal for motorcycles, maintenance equipment and other wet clutch transmission applications. Formulated to prevent clutch glazing and slippage, it insures smooth clutch engagement and long term, dependable transmission operation. AMSOIL Synthetic 10W-40 Motor Oil reduces clutch wear for extended transmission life.

Resists Oxidation and High Temperature Breakdown
AMSOIL Premium Protection Synthetic Motor Oil overcomes the thermal deficiencies common to conventional petroleum oils. Volatilization (burn-off), oxidation and excessive deposit formation from high heat are greatly reduced. Viscosity thickening is controlled and engines run clean, promoting cooler operation and long engine life in air or liquid cooled engines.

Extends Drain Intervals in Gasoline and Diesel Engines
The superior AMSOIL synthetic base stock and additive technology exceeds the requirements of both gasoline and diesel engines. AMSOIL Premium Protection Motor Oil neutralizes acids, disperses soot and lasts longer in service than conventional oils.


You can also order in our new AMSOIL Online Store

    AMSOIL Synthetic 10W-40 Premium Protection Motor Oil is compatible with conventional and synthetic motor oils. Mixing AMSOIL motor oils with other oils, however, will shorten the oil life expectancy and reduce the performance benefits. AMSOIL does not support extended drain intervals where oils have been mixed. Aftermarket oil additives are not recommended for use with AMSOIL Synthetic Oils.

    AMSOIL Synthetic 10W-40 Premium Protection Motor Oil is recommended for use up to 15,000 miles or one year, whichever comes first, in unmodified(1), mechanically sound(2) automotive gasoline or diesel engines. In motorcycles, small engines, stationary engines, heavy equipment and other applications, extend drain intervals based on oil analysis or follow the manufacturer recommended drain interval.

    AMSOIL Ea™ full-flow oil filters are designed for extended drain intervals. They stop smaller particles, flow more oil and last longer than regular filters. For best performance, use AMSOIL Ea™ full-flow oil filters and replace at the time of oil change. Other oil filters should be changed at standard OEM* intervals.

    *OEM - Original Equipment Manufacturer

    (1) Engines operating under modified conditions are excluded from extended drain recommendations. Examples include the use of performance computer chips; non-OEM approved exhaust, fuel or air induction systems; and the use of fuels other than those recommended
    for normal operation by the manufacturer.

    (2) Mechanically sound engines are in good working condition and do not, for example, leak oil or consume excessive amounts, are not worn out, do not overheat, do not leak anti-freeze and have properly working emission control systems. AMSOIL recommends repairing malfunctioning engines prior to the installation of AMSOIL synthetic oils.

    This product is not expected to cause health concerns when used for the intended application and according to the recommendations in the Material Safety Data Sheet (MSDS). MSDS’s are available upon request at 715-392- 7101 or on the AMSOIL Website. Keep Out of Reach of Children. Don’t pollute. Return used oil to collection centers.

    Amsoil is the only choice for top Performance. Enjoy your engine for the first time!



 AMSOIL 10W-40 100% Synthetic Motor Oil (AMO)

Kinematic Viscosity @ 100°C, cSt (ASTM D445)


Kinematic Viscosity @ 40°C, cSt (ASTM D445)


Viscosity Index (ASTM D2270)


Cold Crank Simulator Apparent Viscosity @ -25°C, cP (ASTM D5293)

5429 (-25)

Pour Point °C (°F) (ASTM D92)

-43 (-45)

Flash Point °C (°F) (ASTM D92)

230 (446)

Fire Point °C (°F) (ASTM D92)

250 (482)

Four-Ball Wear Test (ASTM D4172: 40kgf, 150°C, 1800 rpm, 1 hr) Scar diameter, mm


Noack Volatility (ASTM D5800) 250°C for 1 hour, % weight loss


High Temperature/High Shear Viscosity cP, X°C, X s-1 (ASTM D4683)


Total Base Number


AMSOIL AMO also results in a smoother running engine. See for yourself!

Technical Service Bulletin

Date: 8/3/2007

Revision 2: 5/2/11

Subject: Flat Tappet and Camshaft Lobe Lubrication
Technical Service Bulletin
Product Description: AMSOIL Synthetic Motor Oils

Provide facts outlining lubrication requirements of flat tappet camshaft engines and the importance of higher levels of zinc and phosphorus.

Flat tappet camshafts undergo extreme pressure and loads, thus requiring an engine oil that is fortified with antiwear additives to provide premium protection. The severity of higher spring pressure in racing engines also creates the need for additional wear protection.

To preserve catalytic converter life, phosphorus levels in motor oil have been reduced. Concerns have risen that oils containing lower levels of zinc/phosphorus could provide insufficient protection in high-pressure areas of flat tappets and camshaft lobes found in many older and high performance engines.


The most commonly used anti-wear additive in motor oils is zinc dialkyldithiophosphate (ZDDP). ZDDP contains both zinc and phosphorus components working together to provide anti-wear protection, and is most important during cam “break-in” procedures. Proper break-in lubes should be used during the break-in phase for all new or rebuilt engines with flat tappets. These lubricants provide the extra protection required to reduce wear at the point of contact during break-in and help the flat tappet face properly
mate with the cam lobe. Once the break-in phase is completed, AMSOIL motor oils, which are formulated with high levels of zinc and phosphorus, will provide premium protection to flat tappet cams.

The American Petroleum Institute (API) and International Lubricants Standards Approval Committee (ILSAC) have mandated the reduction of phosphorus to extend catalytic converter life. However, reducing the level of ZDDP can
compromise protection to engine components, most notably in flat tappet camshafts. Current API SN and ILSAC GF-5 specifications for gasoline engines have maximum and minimum phosphorus levels of 800 ppm and 600 ppm,
respectively, for SAE 0W-20, SAE 5W-20, SAE 0W-30, SAE 5W-30 and SAE 10W-30 motor oils.

All engines, especially high-performance modified engines, benefit from oils with superior film strength and antiwear properties. The flat tappet/camshaft lobe interface is the one area in an engine that has extreme contact load.
Since this load increases significantly when non-stock, high-pressure valve springs are employed, the use of properly formulated motor oils is extremely important to reduce wear and extend fl at tappet/camshaft life.

Proper assembly lubes and oil additives should be used during the break-in phase for all new or rebuilt engines with flat tappets. These additives provide the extra protection required at the point of contact during break-in to help the flat tappet face to properly mate with the cam lobe. Once the break-in phase is completed, these additives should not be used because of other engine life issues created by long term use of these materials. AMSOIL now provides break-in motor oil products.


AMSOIL Product Name Phosphorus Level
Zinc Level
Primary Recommendations    
Z-ROD™ 10W-30 Synthetic
Motor Oil (ZRT)
1320 1440
Z-ROD™ 20W-50 Synthetic
Motor Oil (ZRF)
1320 1440
Secondary Recommendations    
AMO 10W-40 Synthetic Premium Protection 1265 1378
ARO 20W-50 Synthetic Premium Protection 1266 1379
HDD Series 3000 Synthetic 5W-30 Diesel Oil 1266 1379
AME 15W-40 Synthetic Heavy
Duty Diesel and Marine
Motor Oil
1267 1377
Racing Applications    
Dominator® 5W-20
Synthetic Racing Oil (RD20)
1424 1575
Dominator® 10W-30
Synthetic Racing Oil (RD30)
1424 1575
Dominator® 15W-50
Synthetic Racing Oil (RD50)
1424 1575
SAE 60 Super Heavy Weight
Synthetic Racing Oil (AHR)
1265 1365
Break-In Oil (SAE 30) (BRK) See Datasheet  

AMSOIL AMO, ARO, HDD, TRO, and AHR all contain high levels of zinc/phosphorus maximizing flat tappet/camshaft life in stock and modified applications.

AMSOIL 10W-40 (AMO) and 20W-50 (ARO) are premium synthetic formulations which are recommended for API SL (gasoline)/CI-4 Plus (heavy-duty, on-road diesel) specified applications. They are an outstanding choice where high zinc containing protection is required in late model hot rods requiring extra camshaft protection.

AMSOIL (HDD) is a 5W-30 weight combination diesel/gasoline oil with a higher starting TBN to handle the significant stresses from high soot loading and acid generation in modern diesel engines. HDD contains the high phosphorus and zinc required for long life.

AMSOIL 20W-50 (TRO) is a premium synthetic racing oil with superior film strength and anti-wear protection for gasoline engines. It is an excellent choice for street or race cars, hot rods, trucks or boats. TRO is the preferred choice for highly modified, high horsepower engines requiring the extra protection required by flat tappet camshaft engines.
AMSOIL (AHR) is a super heavy weight racing oil de-signed for alcohol and nitro burning race engines where viscosity loss associated with fuel dilution is a concern. AHR includes a high dose of zinc containing anti-wear chemistry that race engines require.

If you want this motor to sound and feel as good as it looks, ONLY Amsoil will provide that result. Smooth and stedy ride with no worry about temperature - that's AMSOIL Performance.

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