AMSOIL DOMINATOR® 15W-50 100% Synthetic Racing Oil

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AMSOIL DOMINATOR 15W-50 100% Synthetic Racing Oil

AMSOIL DOMINATOR 15W-50 Synthetic Racing Oil is a heavy multi-viscosity race formula built for high-performance gasoline and diesel race engines that call for an SAE 50 grade. The 15W-50 viscosity is the DOMINATOR pick for big-block oval, drag, sprint, endurance and marine race programs running wider bearing clearances, high oil temperatures, and shock-loaded valvetrains. This race-only chemistry runs outside the API ZDDP cap, loading more zinc and phosphorus at the cam, lifter and ring interface than a street-spec motor oil can carry.

High-zinc anti-wear chemistry for big-block and aluminum-block race engines

DOMINATOR 15W-50 is heavily fortified with zinc and phosphorus anti-wear additives that load the cam lobes, lifter faces, rocker tips, wrist pins and ring pack with a sacrificial film before metal-on-metal contact can occur. Independent four-ball wear testing per ASTM D4172 (40 kg load, 150 C, 1,800 rpm, one hour) measures a 0.39 mm wear scar on the 15W-50 grade, well inside the protection range required by aggressive flat-tappet camshafts, high-spring-pressure roller cams and the shock loads common to big-block oval, truck-pull, and aluminum-block builds.

SAE 50 hot film strength for high-temperature endurance

Big-block, drag, marine and endurance race engines run higher oil temperatures and looser bearing clearances than a small-block on a short feature. DOMINATOR 15W-50 holds an in-grade kinematic viscosity of 17.9 cSt at 100 C per ASTM D445 and a high-temperature, high-shear viscosity of 5.4 cP at 150 C per ASTM D5481, supplying thick straight-50 film strength in the rod and main bearings when oil temperature climbs. A flash point of 238 C (460 F) and a fire point of 272 C (522 F) per ASTM D92 give thermal headroom for sustained high-rpm running on long features and back-to-back rounds.

Shear stability that holds grade through long features

Race-engine rpm and bearing shear can knock a poorly stabilized multi-grade out of grade within a few sessions, dropping film thickness in the rod and main bearings exactly when load is highest. DOMINATOR 15W-50 is engineered to resist viscosity loss due to mechanical shear, delivering straight-50 protection across long races, multi-round drag programs and endurance sessions without thinning into a high-30 weight as the run wears on.

Proprietary friction modifier for measurable horsepower

Lower internal friction means more crankshaft horsepower and cooler oil temperatures. DOMINATOR 15W-50 uses a proprietary friction modifier that reduces parasitic drag in the bearings, valvetrain, and timing drive. The same formulation runs in race engines campaigned by AMSOIL corporately sponsored racers including Bryce Menzies and Brad Lovell, with no spec change between the quart on the shelf and the quart that goes into a championship motor.

All-temperature flow and fuel compatibility

A pour point of -38 C (-36 F) per ASTM D97 and a cold-crank simulator viscosity of 6,062 cP at -20 C per ASTM D5293 mean DOMINATOR 15W-50 lays down a protective film on a cold race-day fire-up before oil pressure peaks. Viscosity index of 164 per ASTM D2270 keeps the operating film flat across a wide oil-temperature swing on long features. The formula is compatible with leaded and unleaded gasoline, diesel, alcohol, nitromethane, and nitrous oxide; a total base number of 8.0 supports the acid-neutralization workload from combustion blow-by when running rich, high-lead or alcohol fuels through endurance events.

Recommended applications and service intervals

DOMINATOR 15W-50 is built for domestic and import high-performance racing engines that call for an SAE 50 viscosity. Typical builds and series include:

• Asphalt late model, dirt late model and sprint
• Modified big block, aluminum block and truck-pull
• Endurance and rally programs
• Marine race and diesel racing

Race-engine oil service life is event- and chemistry-driven. When competing, the engine builder or vehicle owner is responsible for setting an appropriate oil change interval based on event length, fuel, rpm range, blow-by, and oil analysis. DOMINATOR is not intended for long-term use in passenger cars and light trucks; engines that see daily-driver service should run an API-licensed AMSOIL Signature Series, XL, or OE motor oil instead. Oil analysis through Oil Analyzers Inc. (715-395-0222), a division of AMSOIL, supports interval and engine-health decisions between rebuilds. Pair DOMINATOR 15W-50 with an AMSOIL EaO or Ea15K race-rated oil filter and a clean break-in protocol; no aftermarket ZDDP, moly or race-additive packages need to be mixed in.

Typical technical properties

Order AMSOIL DOMINATOR 15W-50 Synthetic Racing Oil

DOMINATOR 15W-50 Synthetic Racing Oil ships in quarts (product code RD50QT-EA), cases of 12 quarts (RD50QT-CA), gallon jugs (RD501G-EA) and 55-gallon drums (RD5055-EA), backed by the AMSOIL Limited Warranty for defects in materials and workmanship. For application match beyond a race engine, use the AMSOIL vehicle lookup guide to confirm the right viscosity for a street vehicle, and the AMSOIL car oil guide to compare Signature Series, XL and OE motor oils for daily-driven cars and trucks. Order AMSOIL DOMINATOR 15W-50 100% Synthetic Racing Oil.

Frequently asked questions