AMSOIL ATV/UTV Transmission & Differential Fluid

Based on AMSOIL’s own lookup tools, category pages and “oil change in a box” kits, here’s what stands out from the research:

• The two AMSOIL products most commonly paired with AMSOIL 100% Synthetic ATV/UTV Transmission & Differential Fluid are:
  • AMSOIL 0W-50 100% Synthetic ATV/UTV Motor Oil – used as the matching engine oil in many Polaris, Can-Am and Honda machines.
  • AMSOIL 100% Synthetic ATV/UTV Powertrain Fluid – bundled with the Trans & Diff Fluid in AMSOIL’s own “complete oil change” packages for modern UTVs.

For high-performance cars and trucks that run AMSOIL Signature Series 5W-50 100% Synthetic Motor Oil, the two AMSOIL products most often used alongside it (based on how they’re merchandised together for Mustangs, hot hatches and performance builds) are:

1. AMSOIL SEVERE GEAR 100% Synthetic Gear Lube (75W-90/75W-110/75W-140) – for differentials and final drives.
2. AMSOIL P.i. Performance Improver Gasoline Additive – for deep cleaning injectors and keeping high-output gas engines responsive.

Here’s a full SEO-friendly article about that combo.

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AMSOIL Signature Series 100% Synthetic Motor Oil

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AMSOIL 100% Synthetic Gear Lube

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AMSOIL P.i. Performance Improver and other fuel additives.

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AMSOIL Signature Series 5W-50 100% Synthetic Motor Oil: Built for Serious Power

AMSOIL Signature Series 5W-50 is not a typical passenger-car oil.
It’s aimed at high-output, high-heat performance engines that see track days, hard street driving, or both.

Ford track-oriented engines like the Boss 302, GT350, GT500 and Focus RS are classic examples that call for a 5W-50 grade from the factory.

Signature Series 5W-50 is formulated to:

• Deliver maximum wear protection in extreme heat and high rpm.
• Provide strong film strength under heavy load and boost.
• Resist oxidation and deposit formation far better than conventional oil.
• Support extended drain intervals when used as directed and when conditions allow.

Paired with AMSOIL SEVERE GEAR in the differential and AMSOIL P.i. in the fuel system, it forms a full protection package for serious enthusiasts.

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Understanding What 5W-50 Really Means

What the 5W-50 Viscosity Range Does for You

“5W-50” describes how thick or thin the oil is at different temperatures:

• 5W: Flows quickly in cold temperatures for easy starts and fast protection.
• 50: Maintains a thick, protective film at high operating temperatures.

In practice, that means:

• Confident cranking and oil flow on cold mornings.
• Stable oil pressure when the engine oil is cooked on track sessions.
• Extra margin for supercharged and turbocharged engines that generate a lot of heat.

Why Performance Fords and Other Track Cars Love 5W-50

Ford’s performance manuals specify 5W-50 in:

• Many Shelby GT350 / GT500 applications.
• Boss 302 track cars.
• Focus RS and other modern performance platforms.

These engines can see:

• Long pulls at redline.
• High oil temperatures.
• Heavy loads from boost and sticky tires.

Signature Series 5W-50 is built exactly for this world.

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Inside the Signature Series 5W-50 Formula

Synthetic Base Oils for Stability and Cleanliness

Signature Series 5W-50 uses high-quality synthetic base stocks that resist:

• Thermal breakdown at sustained high temperatures.
• Oxidation, which leads to thickening and sludge.
• Volatility, which reduces oil consumption and deposits in the ring lands.

That stability keeps oil pressure more consistent and helps the engine stay cleaner over time.

Advanced Additives for Wear and Deposit Control

The additive system is tuned for performance:

• Anti-wear additives protect cams, followers and bearings under high load.
• Detergents and dispersants control varnish and deposits.
• Anti-oxidants help the oil handle extended high-temperature operation.

Independent testing shows Signature Series offers significantly more wear protection than industry standards, and improved piston cleanliness versus common OEM-spec oils.

Protection for Turbochargers and Direct Injection

Modern performance engines often combine:

• High boost pressures.
• Direct injection.
• Tight clearances and advanced timing strategies.

Signature Series 5W-50 is designed to:

• Resist turbo coking in the hot turbo center section.
• Help control low-speed pre-ignition (LSPI) in modern direct-injected engines, where applicable.
• Support clean piston crowns and ring lands, which is critical for compression and power.

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Companion Product #1 – AMSOIL SEVERE GEAR 100% Synthetic Gear Lube

Why Gear Lube Matters as Much as Engine Oil

When you upgrade power, tires and driving style, you don’t just stress the engine.
You also hammer on:

• Differentials
• Final drives
• Manual gearboxes and transfer cases

AMSOIL SEVERE GEAR 100% Synthetic Gear Lube is a natural match for builds that step up to Signature Series 5W-50 in the engine bay.

It is engineered for:

• Severe towing, hauling and performance driving.
• High shock loads from launches and aggressive downshifts.
• Extreme temperature swings.

Key Benefits of SEVERE GEAR in a 5W-50 Build

SEVERE GEAR provides:

• Robust EP (extreme-pressure) additives to protect ring and pinion gears.
• Strong resistance to pitting, scoring and micro-welding on gear teeth.
• Excellent performance in both very cold and very hot conditions.

For a typical high-performance street/track car, that means:

• Quiet, smooth differential operation.
• Less risk of gear noise and whine as the miles add up.
• Confidence when launching on sticky tires or running high-speed laps.

How Signature Series 5W-50 and SEVERE GEAR Work Together

Think of the combination like this:

• Signature Series 5W-50 guards the top end, rotating assembly and bearings.
• SEVERE GEAR guards the differential and rear-end gearing.

Together, they create a front-to-back protection package that matches how people actually drive these cars:

• Hard acceleration.
• Track days and spirited canyon runs.
• Occasional towing of small trailers or track support gear.

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Companion Product #2 – AMSOIL P.i. Performance Improver

Keeping the Fuel System Clean in High-Output Engines

High-performance engines rely on precise fuel delivery:

• Multi-hole injectors or direct-injection nozzles.
• Fine spray patterns.
• Tight control from the ECU.

Over time, deposits form on injectors and intake valves, especially with modern fuels. AMSOIL P.i. Performance Improver is a concentrated gasoline additive designed to address that.

It is formulated to:

• Deep-clean injectors and combustion chambers.
• Restore power and throttle response.
• Improve fuel economy in dirty systems.

Why P.i. Pairs Well with 5W-50

When a vehicle is driven hard enough to justify 5W-50, it often sees:

• Short trips mixed with hard pulls.
• Heat-soaked fuel rails.
• Aggressive timing and boost.

In that environment, deposits can build quickly. P.i. helps:

• Maintain consistent combustion.
• Reduce knocking and pinging tendency.
• Keep the ECU from pulling timing due to knock events.

AMSOIL’s own materials and independent reviews show measurable gains in power and fuel economy after a cleaning cycle with P.i. in dirty systems.

A Simple Maintenance Pattern

A common pattern enthusiasts use is:

• Run Signature Series 5W-50 in the engine.
• Use SEVERE GEAR in the differential.
• Treat a full tank with P.i. every 4,000–5,000 miles or so (or as directed).

That gives you:

• Fresh, stable oil film in the engine.
• Strong gear protection at the rear.
• A clean fuel path feeding the combustion chambers.

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Is 5W-50 the Right Signature Series Oil for You?

Start with the Owner’s Manual

Always begin by:

• Checking the recommended viscosity.
• Looking at any special notes for track use or towing.

If your manual specifically calls for 5W-50 (as many track-oriented Ford applications do), Signature Series 5W-50 is a direct upgrade path from the OEM fill.

If the manual lists a different grade, you should:

• Follow OEM specs while under warranty.
• Only deviate when you fully understand the implications.

When 5W-50 Shines

5W-50 is usually a strong choice when:

• The car is supercharged or turbocharged from the factory.
• You run long track sessions or extended high-speed runs.
• Oil temperatures routinely climb above what a 5W-30 or 0W-40 was designed to handle.

The thicker 50-weight at temperature offers extra film strength for:

• Rod and main bearings.
• Camshaft lobes and followers.
• Piston skirts and rings.

When Another Signature Series Grade May Be Better

Other Signature Series viscosities (0W-20, 5W-20, 5W-30, 0W-40, etc.) may be better if:

• The vehicle is a daily driver that never sees track duty.
• The OEM specifically warns against heavier grades for efficiency or design reasons.
• You live in a climate where lighter oils are specified year-round for fuel economy and cold-start behavior.

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Service Intervals and Practical Ownership Tips

Extended Protection, but Smart Intervals

Signature Series oils are built to support extended drain intervals, such as up to 25,000 miles or one year in suitable conditions, when used with appropriate filters and where allowed.

For most owners, a practical approach is:

• Follow the oil-life monitor or severe-service interval while under warranty.
• Use used oil analysis if you want to push beyond standard intervals.
• Always adjust intervals for:
  • Repeated short trips
  • Dusty environments
  • High track time or towing

Filter Choice and Capacity

Pairing Signature Series 5W-50 with a high-efficiency oil filter is smart:

• It helps capture small particles.
• It supports stable oil pressure over extended intervals.

AMSOIL offers Ea® Oil Filters designed to match extended drains and high-performance use in popular applications.

Driving Habits That Help the Oil

Even the best oil works better when you:

• Let the engine reach full operating temperature before going wide-open throttle.
• Avoid long periods of idling.
• Check the oil level regularly, especially between track days.

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Putting It All Together: A Complete Protection Strategy

Engine + Driveline + Fuel System

For a high-performance build that runs hard, a simple three-piece formula works:

• AMSOIL Signature Series 5W-50 100% Synthetic Motor Oil
  • Guards the engine against heat, wear and deposits.
• AMSOIL SEVERE GEAR 100% Synthetic Gear Lube
  • Protects the differential and final drive under extreme loads.
• AMSOIL P.i. Performance Improver
  • Cleans injectors and combustion chambers for crisp, efficient power.

Benefits You Can Feel and Measure

Owners who follow this pattern typically notice:

• Smoother, quieter operation under load.
• More consistent power across the rev range.
• Cleaner oil at drain time compared to conventional or low-tier synthetics.
• A driveline that feels tight and composed, even after many hard miles.

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Frequently Asked Questions about Signature Series 5W-50

Do I have to run 5W-50 all year?

If your owner’s manual calls for 5W-50 year-round, you can use it year-round.
Its synthetic base oils keep cold-start flow strong, even in colder weather.

Is 5W-50 too thick for daily driving?

In engines designed for it, no.
Those applications are tuned for the added film strength, especially at higher oil temperatures.

Can I mix 5W-50 with another viscosity?

You can in an emergency top-off, but it’s better to keep one grade in the crankcase.
Plan ahead and keep a spare quart on hand.

How often should I use P.i. Performance Improver?

Many owners run a treatment every 4,000–5,000 miles or at each oil change, depending on fuel quality and driving style.

Do I still need SEVERE GEAR if my car is stock?

If you drive gently, stock fluids can be serviceable.
If you track the car, tow, or drive hard, SEVERE GEAR is cheap insurance.

Will switching to Signature Series 5W-50 void my warranty?

Use a viscosity and specification that meets or exceeds the OEM requirements and keep receipts.
When in doubt, follow factory recommendations while under warranty and consult AMSOIL’s Product Guide and warranty information.