STP High Mileage Fuel Injector & Carburetor Treatment 5.25 oz — Upper Cylinder Lubricant, Cap‑less Compatible (12 Pack)

STP High Mileage Fuel Injector and Carburetor Treatment is a concentrated bottle formula that cleans fuel injectors and carburetors while lubricating the upper cylinder to help restore smooth starting and steady acceleration.

If carbon, varnish and other fuel deposits are building up in your engine, performance and efficiency can suffer. This STP treatment uses a jet-fuel-based carrier to deliver cleaning agents and a lubricant designed for upper-cylinder protection. Each 5.25-ounce bottle treats up to about 21 gallons of gasoline, and the formula is compatible with vehicles that have cap-less fuel systems, making it versatile for many modern cars and light trucks.

How does this product improve throttle response and starting?

The treatment dissolves and helps remove deposits that form on injectors, carburetor parts and intake components, which can cause hesitation and hard starts. By clearing these obstructions and adding a light upper-cylinder lubricant, combustion becomes more consistent and ignition is aided.

• Breaks down carbon and varnish on injectors and carburetors
• Lubricates valve stems and rings to reduce friction
• Helps restore smoother cold and hot starts

Will it work with modern vehicles and cap-less fuel systems?

Yes — the formula is designed to be cap-less fuel system compatible, so you can add it at the pump without special adapters. It is safe for use in any gasoline engine and formulated to mix with fuel to treat the fuel system while driving.

• Compatible with cap-less fuel inlet designs
• Safe for all gasoline engine types
• No special tools required; pour into the tank during refueling

How much fuel does one bottle treat and how often should I use it?

Each 5.25-ounce bottle treats up to roughly 21 gallons of gasoline, so dosing is simple: one bottle per tank for larger tanks, or adjust proportionally for smaller fills. For regular maintenance, many drivers use a treatment every few fill-ups or follow interval guidance in their vehicle’s service recommendations.

• One bottle treats up to ~21 gallons
• Use every few fill-ups for preventative care
• Use as needed for performance restoration

Is this safe for long-term engine components and fuel system parts?

The product is formulated to be safe for fuel system materials and engine components when used as directed; it focuses on removing deposits without harsh effects on seals or sensors. The lubricant component is meant to reduce upper-cylinder wear, not to alter fuel chemistry in ways that harm catalysts or oxygen sensors.

• Formulated to avoid damage to seals and fuel system parts
• Contains lubricant to reduce upper-cylinder friction
• Designed for routine maintenance and targeted cleaning needs

Who is this for: Drivers who want to maintain or restore gasoline engine performance — especially those with higher-mileage vehicles, cars showing mild hesitation or rough idling, or anyone wanting periodic preventative care. It’s also a practical choice for fleet managers and DIY enthusiasts looking for a straightforward, cap-less compatible treatment to keep injectors and carburetors cleaner between professional services.