Car engine oil additives are designed to enhance oil performance, reduce wear, and extend engine life. The best overall pick, LIQUI MOLY Cera Tec, offers excellent wear protection with ceramic technology, but it comes at a higher price. Lucas Oil High Mileage Oil Stabilizer is a great choice for aging engines, providing added protection and smooth operation. However, many additives trade off between cost and effectiveness, with some promising performance but lacking long-term benefits. Keep reading to see how these options compare on key factors like performance, ease of use, and value.
Key Takeaways
- Top-performing additives often combine advanced ceramic or nano-technology for maximum engine protection.
- Value options tend to focus on wear reduction and fuel economy but may lack some premium features.
- Ease of use varies, with some products requiring mixing or special application steps.
- Long-term durability benefits are more noticeable with higher-end formulations like ceramic or nano-additives.
- Price does not always correlate directly with effectiveness; understanding your engine’s needs is key.
| STP High Mileage Oil Treatment + Stop Leak – 15 FL OZ |  | Best for High-Mileage Vehicles Needing Seal Rejuvenation | Volume: 15 FL OZ | Suitable for: Cars, light trucks, SUVs | Formulation: High-viscosity oil treatment with ZDDP additive | VIEW LATEST PRICE | See Our Full Breakdown |
| DWD2 Clean Metal™ Conditioner – Engine Oil Additive, 7 oz. |  | Best for Engine Performance and Fuel Efficiency | Volume: 7 oz. | Type: Engine Oil Additive | Technology: Nano-Technology | VIEW LATEST PRICE | See Our Full Breakdown |
| LIQUI MOLY Oil Additive Cera Tec 20002 Ceramic Wear & Tear Protection, 300 ml |  | Best for Friction Reduction and Wear Protection | Volume: 300 ml | Compatibility: Petrol & Diesel Engines | Features: Reduces friction, wear protection, stable under high temperatures | VIEW LATEST PRICE | See Our Full Breakdown |
| AtomOil Oil Additive for Car Engine and Protection, 16 Oz |  | Best for Cold Starts and Sludge Prevention | Container Type: Bottle | Compatible Vehicle Type: Car | Fit Type: Universal Fit | VIEW LATEST PRICE | See Our Full Breakdown |
| Prolube Oil Treatment – Engine Oil Additive for Gas & Diesel Engines – 16oz |  | Best for Engine Performance and Noise Reduction | Volume: 16oz | Compatibility: Gasoline and diesel engines, transmissions, differentials | Application: 1 oz per quart for standard engines, 2 oz per quart for high-mileage engines | VIEW LATEST PRICE | See Our Full Breakdown |
| Lucas Oil 10118 High Mileage Oil Stabilizer – 1 Quart |  | Best for Worn Engines Needing Longevity Boost | Volume: 1 Quart | VIEW LATEST PRICE | See Our Full Breakdown | ||
| BestLine Racing Nano-Diamond Engine Oil Additive for Gas & Diesel Engines |  | Best for Maximum Friction Reduction and Power Restoration | Treats: 9-10 gallons of oil | Temperature Resistance: up to 1,800°F | Nanoparticle Size: 5-10nm | VIEW LATEST PRICE | See Our Full Breakdown |
| XADO Engine Oil Additive for Wear Protection and Rebuilding |  | Best for Engine Rebuilding and Long-Term Wear Protection | Application: Gasoline and diesel engines | Capacity: Up to 5 quarts | Volume: 225 ml | VIEW LATEST PRICE | See Our Full Breakdown |
| Prolube Oil Treatment – Engine Oil Additive for Gas & Diesel Engines – Reduces Wear, Noise, Vibration – Boosts Fuel Economy & Horsepower – Works on Transmissions & Differentials (1QT) |  | Best for Versatile Performance Across Engines and Components | Volume: 1 quart | Compatibility: Gasoline and diesel engines, transmissions, differentials | Application Ratio: 1 oz per quart | VIEW LATEST PRICE | See Our Full Breakdown |
| Engine Oil Additive & Treatment – Diamond Nano-Lube by BestLine Racing – Reduces Friction Up to 60% – For Gas & Diesel Engines |  | Best for High-Performance Friction and Heat Resistance | Application: Gasoline, diesel, hybrid, racing engines | Friction Reduction: Up to 60% | Temperature Resistance: up to 1,800°F | VIEW LATEST PRICE | See Our Full Breakdown |
| Lucas Oil 10001 Heavy Duty Oil Stabilizer – 1 Quart |  | Best for Heavy-Duty, Professional-Grade Engine Support | Volume: 1 Quart | Formulation: 100% petroleum | Use: Heavy-duty, suitable for new engines | VIEW LATEST PRICE | See Our Full Breakdown |
| car engine oil additife | Volume |
|---|---|
| STP High Mileage Oil Treatment | 15 FL OZ |
| DWD2 Clean Metal™ Conditioner | 7 oz. |
| LIQUI MOLY Oil Additive Cera T | 300 ml |
| AtomOil Oil Additive for Car E | — |
| Prolube Oil Treatment | 16oz |
| Lucas Oil 10118 High Mileage O | 1 Quart |
| BestLine Racing Nano-Diamond E | — |
| XADO Engine Oil Additive for W | 225 ml |
| Prolube Oil Treatment | 1 quart |
| Engine Oil Additive & Treatmen | — |
| Lucas Oil 10001 Heavy Duty Oil | 1 Quart |
More Details on Our Top Picks
STP High Mileage Oil Treatment + Stop Leak – 15 FL OZ
This high-viscosity additive is tailored specifically for engines with over 75,000 miles, making it ideal for extending the life of aging engines. Its formulation, enriched with ZDDP, not only reduces wear but also helps rejuvenate seals and gaskets, which is a clear advantage over typical oil treatments that don’t address leaks directly. Compared with Prolube Oil Treatment, which offers broader engine performance boosts, this product emphasizes leak stop and seal restoration, though it’s limited strictly to high-mileage engines. The tradeoff is that it’s not suitable for newer vehicles or engines under warranty, where such high viscosity might cause oil flow issues. If your engine is aging and leaks or noise are concerns, this pick makes the most sense.
Pros:- Protects high-mileage engines from wear
- Helps stop leaks and reduce engine noise
- Rejuvenates seals and gaskets
Cons:- Only suitable for high-mileage vehicles
- Requires addition during oil changes, not a standalone solution
Best for: Owners of high-mileage cars seeking to reduce leaks and engine noise without major repairs
Not ideal for: Drivers with newer vehicles or those seeking a universal additive for all engine types
- Volume:15 FL OZ
- Suitable for:Cars, light trucks, SUVs
- Formulation:High-viscosity oil treatment with ZDDP additive
Our verdict“This additive is best for owners of older vehicles experiencing leaks and seal degradation who want targeted restoration.”
DWD2 Clean Metal™ Conditioner – Engine Oil Additive, 7 oz.
This professional-grade additive stands out for its ability to reduce heat and friction, translating into smoother running engines and better fuel economy. Its nano-technology enhances oil’s ability to suspend carbon deposits, which is a step above traditional additives like LIQUI MOLY Cera Tec, that focus mainly on wear protection. Compared with Prolube Oil Treatment, which emphasizes engine longevity and noise reduction, DWD2’s strength lies in optimizing performance and reducing heat, making it suitable for drivers who want a cleaner, more efficient engine. The main consideration is the limited information on its long-term effects, which might concern cautious users. For those looking to improve engine thermal management and efficiency, this additive makes a compelling choice.
Pros:- Reduces heat and friction for smoother engine operation
- Compatible with various engine types and oils
- Enhances fuel economy and engine performance
- Extends engine life by suspending carbon deposits
Cons:- Limited long-term performance data
- Requires proper dosage for best results
Best for: Performance-conscious drivers seeking smoother operation and fuel savings
Not ideal for: Owners of engines with very high mileage or severe leaks, where seal rejuvenation is a priority
- Volume:7 oz.
- Type:Engine Oil Additive
- Technology:Nano-Technology
- Compatibility:Gasoline & Diesel Engines, Synthetic & Non-Synthetic Oils
Our verdict“Ideal for drivers wanting to boost performance and fuel efficiency without extensive engine overhaul.”
LIQUI MOLY Oil Additive Cera Tec 20002 Ceramic Wear & Tear Protection, 300 ml
Compared with DWD2 Clean Metal™ Conditioner, Cera Tec emphasizes ceramic protection to reduce friction and wear, making it suited for drivers who prioritize engine longevity and thermal stability. It’s compatible with all motor oils, which broadens its usability, but the lack of specific user reviews or extensive performance data makes it harder to gauge long-term benefits. This product is especially effective under high thermal and dynamic loads, providing a layer of protection that can help prevent engine component wear. However, its limited transparency regarding real-world effects and absence of long-term testing details may be a concern for cautious buyers. For those seeking a proven ceramic-based wear protector, this option is worth considering.
Pros:- Reduces engine friction and wear
- Compatible with all motor oils and filters
- Stable under high temperatures and loads
Cons:- No specific user reviews or long-term data
- Limited information on real-world performance
Best for: Owners of engines exposed to high thermal stress or high-mileage engines needing wear protection
Not ideal for: Casual drivers or those seeking performance boosts rather than wear protection
- Volume:300 ml
- Compatibility:Petrol & Diesel Engines
- Features:Reduces friction, wear protection, stable under high temperatures
Our verdict“This additive suits owners looking for ceramic-based wear protection and thermal stability in demanding engine conditions.”
AtomOil Oil Additive for Car Engine and Protection, 16 Oz
This additive emphasizes high-temperature stability and cold start protection, making it a solid choice for drivers in colder climates or those looking to extend intervals between oil changes. Its nano-engineered formula helps reduce sludge and contaminants, similar to Prolube Oil Treatment, but with a focus on early film formation for cold starts. Unlike LIQUI MOLY Cera Tec, which highlights wear protection, AtomOil’s strength is in maintaining engine cleanliness and ensuring smooth operation during cold conditions. The main drawback is that it requires a full bottle addition during each oil change, which could be a limitation for those with multiple vehicles or who prefer quick, one-step solutions. This pick makes sense for cold-weather drivers or those prioritizing engine cleanliness.
Pros:- Provides high-temperature engine stability
- Protects during cold starts with early film activation
- Reduces sludge and contaminants
Cons:- Requires adding entire bottle during oil change
- Effectiveness depends on proper application
Best for: Drivers in colder climates or those needing enhanced cold start protection
Not ideal for: Owners of high-mileage engines or those seeking leak sealing or seal rejuvenation
- Container Type:Bottle
- Compatible Vehicle Type:Car
- Fit Type:Universal Fit
- Liquid Volume:16 Fluid Ounces
Our verdict“This additive is best suited for cold climate drivers who want improved cold start performance and sludge control.”
Prolube Oil Treatment – Engine Oil Additive for Gas & Diesel Engines – 16oz
Compared with LIQUI MOLY Cera Tec or DWD2 Clean Metal™, Prolube emphasizes reducing engine noise, vibrations, and wear while boosting horsepower, making it a favorite among performance enthusiasts. Its versatility across gasoline, diesel, transmissions, and differentials adds to its appeal. This product is particularly effective when mixed correctly—1 oz per quart—yet its effectiveness can fluctuate based on engine condition and proper application. While it offers tangible improvements in engine smoothness and efficiency, it may fall short for owners seeking targeted leak repair or seal rejuvenation. If your goal is to improve overall engine feel and longevity, this additive delivers noticeable benefits.
Pros:- Increases horsepower and engine efficiency
- Reduces noise, vibrations, and engine wear
- Works across various engine types and oils
Cons:- Requires proper mixing for best results
- Effectiveness varies with engine condition
Best for: Performance-oriented drivers who want to reduce engine noise and improve efficiency
Not ideal for: Owners of high-mileage engines with leaks or needing seal rejuvenation
- Volume:16oz
- Compatibility:Gasoline and diesel engines, transmissions, differentials
- Application:1 oz per quart for standard engines, 2 oz per quart for high-mileage engines
Our verdict“This additive suits drivers seeking an easy way to boost engine smoothness and reduce noise with minimal fuss.”
Lucas Oil 10118 High Mileage Oil Stabilizer – 1 Quart
This high mileage oil stabilizer stands out for its focus on reducing wear and engine noise, making it a solid choice for older vehicles with high mileage. Unlike products like XADO, which rebuild engine surfaces, Lucas Oil 10118 targets lubrication to minimize deterioration over time. Its ability to cut emissions and oil consumption can extend engine life, but it offers limited info on compatibility with all engine types, which could be a concern for newer or specialized engines. This makes it ideal for owners of aging vehicles seeking a straightforward solution to improve performance and reduce engine noise.
Pros:- Reduces engine wear and prolongs engine life
- Minimizes engine noise and emissions
- Helps decrease oil consumption
Cons:- Limited info on compatibility with all engine types
- No customer reviews or ratings available
Best for: Owners of high-mileage vehicles experiencing increased engine noise and oil consumption
Not ideal for: New car owners with under 50,000 miles seeking performance upgrades, as the product focuses on worn engines
- Volume:1 Quart
Our verdict“This stabilizer is best suited for older engines requiring lubrication and noise reduction, not for new or high-performance engines.”
BestLine Racing Nano-Diamond Engine Oil Additive for Gas & Diesel Engines
This nano-diamond additive excels in reducing engine friction by up to 60%, which translates into noticeable decreases in noise, vibration, and wear. Compared with Prolube, which emphasizes general performance boosts, BestLine Racing focuses on extreme friction reduction and heat resistance, making it suitable for racing or high-performance engines. The formula’s ability to withstand temperatures up to 1,800°F ensures protection under demanding conditions, but consistent use at every oil change is recommended for best results, and benefits may vary based on engine condition. It’s an excellent choice for those seeking to restore engine power and longevity across various vehicle types.
Pros:- Reduces engine friction and noise substantially
- Restores engine power and extends engine life
- Universal compatibility with all engine types
Cons:- Requires consistent use at each oil change for optimal results
- Performance benefits can depend on engine condition
Best for: Car enthusiasts and racers wanting maximum friction reduction and engine performance restoration
Not ideal for: Casual drivers or those with engines in good condition who don’t need aggressive friction reduction
- Treats:9-10 gallons of oil
- Temperature Resistance:up to 1,800°F
- Nanoparticle Size:5-10nm
- Application:Gasoline, diesel, hybrid, racing engines
Our verdict“This additive is ideal for high-performance engines needing friction reduction and power restoration, but benefits depend on regular application and engine state.”
XADO Engine Oil Additive for Wear Protection and Rebuilding
XADO’s additive distinguishes itself by actively rebuilding worn metal surfaces using its Revitalizant technology. Unlike the friction reducers like Diamond Nano-Lube, which focus on reducing current wear, XADO aims to restore damaged engine parts and provide long-lasting protection for up to 60,000 miles. It’s especially suited for engines with significant wear or those approaching overhaul, but requires a full treatment with one bottle for optimal results. Its capacity is limited to engines with up to 5 quarts, so larger engines may need multiple treatments. This product excels in restoring engine health but is less suitable for routine maintenance or newer engines without wear issues.
Pros:- Rebuilds worn metal surfaces and restores engine components
- Enhances power, acceleration, and fuel efficiency
- Provides long-lasting protection for up to 60,000 miles
Cons:- Requires a complete treatment for best results
- Limited to engines with up to 5 quarts capacity
Best for: Owners of worn or aging engines in need of rebuilding or long-term wear protection
Not ideal for: New or lightly used engines that do not exhibit wear, as the product’s rebuilding benefits are unnecessary in such cases
- Application:Gasoline and diesel engines
- Capacity:Up to 5 quarts
- Volume:225 ml
- Duration:Up to 60,000 miles
Our verdict“XADO is a smart choice for engines needing repair and rebuilding, but less so for routine or preventive maintenance in healthy engines.”
Prolube Oil Treatment – Engine Oil Additive for Gas & Diesel Engines – Reduces Wear, Noise, Vibration – Boosts Fuel Economy & Horsepower – Works on Transmissions & Differentials (1QT)
Prolube Oil Treatment offers a broad approach, improving horsepower, reducing noise, and extending engine lifespan across various applications, including transmissions and differentials. Unlike specialized additives like Diamond Nano-Lube or XADO, this product emphasizes versatility, making it suitable for owners seeking an all-in-one solution. It requires precise mixing ratios—1 oz per quart for standard engines—and its effectiveness depends on engine condition, which might limit benefits in heavily worn engines. Its compatibility with both synthetic and conventional oils makes it attractive for diverse vehicle types, but users should be mindful of correct dosing for optimal results.
Pros:- Enhances horsepower and engine performance
- Reduces noise and vibrations effectively
- Compatible with synthetic and conventional oils
Cons:- Requires precise mixing ratios for best results
- Effectiveness varies with engine condition
- Limited to 1-quart bottles, may need multiple doses for larger engines
Best for: Vehicle owners seeking a multi-purpose additive to improve performance and longevity across various engine and transmission components
Not ideal for: Those expecting dramatic, immediate performance gains or with engines in excellent condition, since its benefits are more conservative and condition-dependent
- Volume:1 quart
- Compatibility:Gasoline and diesel engines, transmissions, differentials
- Application Ratio:1 oz per quart
Our verdict“This additive suits owners looking for a flexible product that improves multiple aspects of engine and drivetrain performance, provided dosing is accurate.”
Engine Oil Additive & Treatment – Diamond Nano-Lube by BestLine Racing – Reduces Friction Up to 60% – For Gas & Diesel Engines
Diamond Nano-Lube makes a compelling case for significant friction reduction, with claims of up to 60%, which can lead to quieter operation, increased power, and extended engine life. Its nanoparticle technology is similar to BestLine Racing, but emphasizes high heat resistance, making it well-suited for racing or heavily stressed engines. However, the presence of nanoparticles may raise questions for some users concerned about long-term effects or environmental impact. Proper dosing at every oil change is essential, and engine condition can influence its effectiveness. This product is targeted at high-performance or racing engines where reducing heat and friction can provide tangible benefits.
Pros:- Reduces engine friction and noise substantially
- Extends engine power and lifespan
- High temperature resistance up to 1,800°F
Cons:- Effectiveness depends on engine condition
- Requires careful dosing at each oil change
- Contains nanoparticles that may concern some users
Best for: High-performance, racing, or heavily stressed engines needing maximum friction reduction and heat resistance
Not ideal for: Everyday commuter vehicles with no performance issues, as the product’s benefits may be overkill and cost-prohibitive
- Application:Gasoline, diesel, hybrid, racing engines
- Friction Reduction:Up to 60%
- Temperature Resistance:up to 1,800°F
- Nanoparticle Size:5-10nm
- Usage:One bottle per 5 quarts of oil, use at every oil change
Our verdict“This additive is best for high-performance engines where maximum friction reduction and heat resistance are needed, but it’s overkill for typical daily drivers.”
Lucas Oil 10001 Heavy Duty Oil Stabilizer – 1 Quart
This heavy-duty oil stabilizer from Lucas Oil stands out for its professional trust and versatility in demanding conditions, making it ideal for engines operating under high stress or load. Compared with the Prolube Oil Treatment, which emphasizes reducing wear and improving fuel economy, this stabilizer is more focused on maintaining oil stability in tough environments, but it provides less specific data on measurable performance gains. Its formulation of 100% petroleum ensures compatibility with most engines, especially newer ones, though it lacks detailed information on performance improvements or compatibility with all engine types. This product is a solid choice for mechanics or vehicle owners who need a reliable additive for heavy-duty or new engine applications without needing detailed additive benefits like ceramic protection or friction reduction. However, it may not be the best for those seeking specific wear reduction or fuel efficiency features, as it primarily offers stability under stress.
Pros:- Trusted by professionals for heavy-duty applications
- Suitable for new engines needing stability
- Versatile multi-use additive for various engine conditions
Cons:- Limited details on specific performance improvements
- No clear information on compatibility with all engine types
Best for: Professionals and vehicle owners operating heavy-duty or new engines requiring stability under demanding conditions
Not ideal for: Owners of older, high-mileage engines looking for wear protection or fuel economy benefits
- Volume:1 Quart
- Formulation:100% petroleum
- Use:Heavy-duty, suitable for new engines
Our verdict“This product makes the most sense for those needing a durable, professional-grade stabilizer for new or heavy-duty engines, but it offers fewer measurable benefits for casual users.”
How We Picked
The products in this roundup were selected based on their formulation quality, user reviews, and proven performance benefits. We prioritized additives that offer tangible improvements in wear protection, engine cleanliness, and fuel efficiency. Ease of application and compatibility with different engine types also influenced rankings. Cost-effectiveness was considered, but premium formulations were favored for their advanced technology. Our goal was to identify options suitable for a range of drivers—from those seeking basic protection to owners of high-mileage engines looking for maximum durability.Factors to Consider When Choosing Car Engine Oil Additives
Choosing the right car engine oil additive involves understanding your engine’s condition, driving habits, and budget. Not all additives are created equal, and selecting the wrong one can lead to wasted money or even engine trouble. This guide highlights key factors to consider to ensure you pick the best product for your needs, avoiding common pitfalls along the way.Compatibility with Engine Type
Not all additives work equally well with gasoline, diesel, or high-mileage engines. Make sure the product you choose explicitly states compatibility with your vehicle. Using an incompatible additive can cause improper lubrication or chemical reactions, potentially damaging your engine. Always check the manufacturer’s recommendations before adding any supplement.
Formulation Technology
Modern additives often incorporate ceramic, nano-technology, or advanced polymers. These formulations can significantly enhance wear protection and engine cleanliness. However, they tend to be more expensive. Consider whether your engine needs a simple protective boost or if investing in high-tech formulations provides enough value for your specific driving pattern.
Ease of Use and Application
Some products are straightforward to add during routine oil changes, while others require pre-mixing or specific procedures. Ease of application can affect how often you use the additive and whether it fits into your maintenance routine. Read labels carefully and choose a product that aligns with your comfort level and schedule.
Cost versus Long-term Benefits
Higher-priced additives often deliver superior protection, longer-lasting effects, and additional benefits like fuel economy gains. Cheaper options might save money upfront but could lack durability or advanced technology. Balance your budget with the expected longevity and performance improvements to avoid short-term fixes that don’t pay off over time.
Specific Engine or Use-Case Needs
If you own a high-mileage vehicle, look for additives designed to restore seals and reduce leaks. For performance or racing engines, products with nano-diamonds or ceramic compounds may provide extra friction reduction. Consider your primary concern—whether it’s longevity, power, or fuel efficiency—and choose accordingly to get the best results.
Frequently Asked Questions
Can I add an oil additive to my engine without changing the oil?
In most cases, adding an oil additive to existing oil without an oil change can provide some benefits, such as reducing friction or sealing minor leaks. However, for maximum effectiveness, it’s recommended to perform a full oil change periodically, especially if your oil is old or contaminated. Using additives as a supplement rather than a replacement for fresh oil ensures your engine benefits from both fresh lubricant and the additive’s properties.
Are oil additives safe for all engine types?
Most modern oil additives are formulated to be compatible with a wide range of engines, including gasoline and diesel. Nonetheless, always check the product label for specific compatibility notes. Some older engines or high-performance models might require specialized formulations, so consulting your vehicle’s manual or a mechanic is advisable before use. Using an incompatible additive can sometimes lead to issues like clogging or chemical reactions that harm your engine.
Will using an additive extend my engine’s lifespan?
When chosen carefully, high-quality oil additives can reduce wear, clean deposits, and protect engine components, potentially extending your engine’s lifespan. However, they are most effective when combined with proper maintenance, regular oil changes, and driving habits. Relying solely on additives without routine upkeep is unlikely to produce significant longevity benefits, so view them as a part of a comprehensive maintenance plan.
How often should I use an engine oil additive?
The frequency of additive use depends on the product and your engine’s condition. Many are designed to be added at every oil change, typically every 3,000 to 5,000 miles. Some products aimed at high-mileage engines can be used more frequently for ongoing protection. Always follow the manufacturer’s instructions, and avoid over-application, which could dilute the oil or cause chemical buildup.
Is it worth paying extra for premium additives?
Premium additives often incorporate advanced ceramic or nano-technology that provides superior wear protection, fuel economy, and engine cleanliness. If you own a high-mileage or high-performance vehicle, investing in these formulations can pay off through extended engine life and better efficiency. However, for older or basic vehicles, a mid-range additive might suffice, and the extra cost may not yield proportional benefits.
Conclusion
For drivers seeking the best overall protection, LIQUI MOLY Cera Tec offers advanced ceramic technology that guards against wear and deposits, making it ideal for those willing to invest in long-term engine health. If you’re on a budget but want reliable protection, Lucas Oil High Mileage Oil Stabilizer provides good value for aging engines. Beginners or those cautious about compatibility might prefer simpler formulations like Prolube Oil Treatment with straightforward application. For high-performance or racing enthusiasts, products featuring nano-diamonds or ceramic compounds, such as BestLine Racing Nano-Diamond, deliver maximum friction reduction and power gains. Ultimately, selecting the right additive depends on your engine’s age, condition, and your driving priorities.
