As an engine gets older, it naturally becomes weaker, and components begin to break down. If you properly care for and maintain the old engine, it's going to provide better performance and a longer life. To do this, you want to consider adding the best oil additive for older engines. We will look at the various formulas available and discuss which is the best option for your worn-down engine.


Preview

Product

Weight/Capacity

Engine/Motor Oil Compatibility

Check Price

Lucas Oil 10002 Heavy Duty Oil Stabilizer, 1...

Lucas Oil LUC10002

128 ounces (1 gallon)

Any, expect Ford PowerStroke

Slick 50 750002 Recharged High Mileage Engine...

Slick 50 750002

15 ounces

Any

Marvel MM13R Mystery Oil - 32 oz.

Marvel Mystery Oil MM13R

16, 32, 128 ounces

Any

Archoil AR9100 Oil Additive (16oz) for All...

Archoil AR9100

16 ounces

Any

Restore 00016 Engine, 16. Fluid_Ounces

Restore 00016

16 ounces

Any, except PowerStroke

STP 15604B High Mileage Oil Treatment Stop...

STP 15604B

15 ounces

Any

Bar's Leaks Engine Treatment Specially...

Bar's Leaks 4102

16.9 ounces

Any


Types of Oil Additives

Complete Engine Treatment

A complete engine treatment will lubricate and clean the engine parts. It’s the best oil additive for older engines if you already have a properly functioning motor that you want to extend the life of.

Engine Break-In Oil Additive

This formula protects the camshaft lifters and valve train as the engine is breaking in. That’s why it isn’t often used with a high-mileage motor.

Engine Oil Stop Leak

This solution will stop and seal the motor oil leaks if they are caused by engine wear. Many leaks are stopped due to some reconditioning of the gaskets and seals.

Heavy Duty Oil Stabilizer

This product is used to reduce friction and eliminate dry start issues. It changes the oil viscosity for older engines to reduce the operating temperatures and oil consumption.

High Mileage Oil Stabilizer

These oil additives for older engines create a coat that covers the metallic surfaces. With this protection, dry start issues are eliminated, and wear is reduced. 


How Oil Additives Work & Their Benefits

Oil additives are made from chemical compounds that change the lubrication of the motor oil. With the best additive to motor oil for older engines, there are several benefits. Some formulas reduce rust while improving engine performance. Furthermore, the additive should clean out the engine to prolong its life. If your motor is smoking or leaking, the right additive will also address these issues as well. The best additives also increase fuel economy, clean out the existing sludge, and increase friction resistance.


Factors to Consider When Choosing Oil Additives

Purpose or Range of Use

As shown above, each older engine additive has a different purpose. You will need to figure out what your goal is and use a product created for that purpose. Some of the additives are universal and accomplish multiple functions at the same time, but you will pay more for these.

Chemical Composition

Some chemicals are going to create more problems for your older engine. Just because it is advertised as the best on the market, doesn't mean you need to believe the statement. Instead, do your research to determine if it has the chemical compound to help your older engine.

Mile Per Gallon Increase

If you want to increase the fuel economy, you must choose the oil additive that’s designed for that purpose. While many formulas help the engine run more efficiently, which turns into saving money at the pump, some excel in this area. Just remember to factor in the fuel savings versus the cost of the additive to make sure you get a good value.

Oil Viscosity

To improve the oil pressure and decrease engine friction, you want high-viscosity oil. Using a heavier oil for older engines allows for maximum protection and superior life. Look for a product that increases the viscosity to help your car motor run for many more years. This provides the lubrication of the metal parts required for proper function.

Rust Prevention

As the car engine gets older, it is more prone to rust. By using a special additive that keeps the engine lubricated, you ensure a reduction of rust development. Plus, an additive with detergents included will help to clean out any current rust within the system for better performance and efficiency.

Reduce Emissions

As the engine runs its best, you can expect a natural reduction in emissions. Instead of the older engine producing unusable products, it will improve the fuel economy by using all of the gasoline or diesel fuel effectively. As the fuel economy improves, so will your costs at the fuel pump.

Engine Compatibility

Not every oil additive will work on any older engine. You must first confirm that the product is meant for older motors. Then, you need to confirm what type of fuel it works with. The best oil additive for older diesel engines isn’t always going to be the same as a formula for gas engines.

Friction Reduction Between Engine Parts

To help the motor run its best, you want a product that increases the lubrication of the metal parts. A higher viscosity oil for older engines will create more lubrication and protect the components from further wear. Not every oil additive offers this type of protection, so read the descriptions carefully.

Dislodge Contaminants or Deposit Sludge

If the oil additive has detergents included, it will clean out the gunk already in the motor. Many engines have sludge inside that decreases performance, but the right solution breaks that free and dislodges contaminants that could lead to engine failure. Read the ingredients to determine what type of detergents are used.


7 Best Oil Additives for Older Engines Reviewed

1. Lucas Oil LUC10002

Our Top Pick!

Weight/Capacity

128 ounces (1 gallon)

Cleans Sludge?

Yes

Reduce Friction?

Yes

Chemical Composition

Petroleum

Key Feature

Stabilizes oil

Engine/Motor Oil Compatibility

Any, expect Ford PowerStroke

If you want a trustworthy oil additive, it makes sense to see what Lucas is offering. This company has become a leader in the industry because their products work. This particular formula is available in a gallon, so you will have plenty to get the job done. You can expect a 50 percent increase in oil life and a reduction in consumption. 

This 100 percent petroleum-based product also eliminates dry start issues while reducing friction. Because it increases the oil pressure, you can expect even more lubrication. With the engine running more efficiently, you will also see an increase in fuel economy, which helps you save more money. This Lucas brand additive also reduces noise, stops oil leaks, and has high detergent action for a cleaner engine.

This top pick formula is used in any gasoline or diesel engine, even your motorcycle. The only engine you won’t want to put it in is a Ford PowerStroke. This bottle warns explicitly against it, so you don't want to damage the motor by trying it anyway. For how exceptional this formula is, the price is reasonable, especially since you can buy it by the gallon. We expect this to extend the life of most older engines.

Pros

  • Eliminates dry start issues
  • Reduces friction
  • Available in a gallon container
  • High detergent action

Cons

  • Doesn’t work with Ford PowerStroke engines

2. Slick 50 750002

Best For High Mileage Older Engines

Weight/Capacity

15 ounces

Cleans Sludge?

Yes

Reduce Friction?

Yes

Chemical Composition

Teflon

Key Feature

Includes powerful detergents

Engine/Motor Oil Compatibility

Any

You can recharge your older engine oil with this high-mileage solution. It protects against friction, wear, and heat. Plus, if the engine oil is leaking, you can count on this product to revitalize the seal and stop the seepage. If the engine isn't leaking now, this solution helps to prevent it from occurring in the first place.

With the powerful detergents included, this additive doesn’t just reduce friction, but also removes and prevents sludge. You can add it during your oil change or put it in the oil at any time to replace lost content. It comes in a handy 15-ounce bottle that’s perfect for carrying in your automobile. The price is a little higher than some engine additives but worth the cost according to the Slick engine additive reviews.

This product comes in 10W-30 oil, which is multi-grade but is also compatible with other mono- and multi-grade options. Use it with your conventional or synthetic motor oils without any trouble. Many people hail it as one of the best oil additives for older diesel engines. The manufacturer also makes a fuel treatment, but that is not compatible with diesel engines. This particular formula will last 5,000 miles, so you should be able to notice a difference right away.

Pros

  • Reduces friction
  • Available in small, portable bottle
  • Multi-grade
  • Fast-acting

Cons

  • Pricey

3. Marvel Mystery Oil MM13R

Best Rated For Old Engines

Weight/Capacity

16, 32, 128 ounces

Cleans Sludge?

Yes

Reduce Friction?

Yes

Chemical Composition

Mineral oil

Key Feature

Cleans buildup

Engine/Motor Oil Compatibility

Any

The Marvel Mystery Oil comes in a variety of sizes, so you can get just what you need. This formula doesn’t just clean the fuel injectors and carburetors but also lubricates the system. With the detergents included, varnish and build-up are also reduced and prevented. Furthermore, you can expect valve sticking and clatter to be minimized. Extreme temperatures will cause oil breakdown, but you can avoid that with this solution.

With the Marvel Mystery Oil, you clean out the engine, increase fuel economy, and protect your older engine. If you use it regularly, you will find a smoother and quieter engine. Plus, it will work with both gasoline and diesel engines.

You don’t even need to spend a lot of money to get your hands on this oil treatment. Plus, when you look at the Marvel Mystery Oil reviews, you see an overwhelming response of five-star comments. The only trouble people seem to have is a delay in results. It could take a few trips to the store before you notice anything occurring. Still, for the cost savings and the overall results, it makes sense to give this product a try if you want to extend the life of your older engine.

Pros

  • Exceptional lubrication
  • Quiets engine operation
  • Reasonable cost
  • Available in multiple sizes

Cons

  • Takes time to work

4. Archoil AR9100

Highest Quality Option For All Engine Types

Weight/Capacity

16 ounces

Cleans Sludge?

Yes

Reduce Friction?

Yes

Chemical Composition

Nanoparticles

Key Feature

Works with PowerStroke problems

Engine/Motor Oil Compatibility

Any

Few oil additives have the reviews that the Archoil product has. This 16-ounce friction modifier can be used on a multitude of vehicles but is especially known for fixing PowerStroke issues stemming from the cold start injector problems. You can use it with the 6.0 and 7.3-liter PowerStroke for fast results. It's also helpful in gearboxes, differentials, hydraulics, and power steering systems, making it a great value for the money.

Over time, it will reduce wear and prolong component life. It also reduces engine noise, friction, heat, and vibration. You can expect Archoil to prevent and clean sludge or varnish deposits for a durable engine life. Plus, it extends the intervals between oil changes, which also helps you to save money. You want to apply one bottle for a Ford PowerStroke, 1.2-ounces per quart of engine oil, or 3.2-ounces for hydraulic oil or power steering fluid.

Use this product with every oil change for the best results. Of course, this capability comes with a higher price, but we still consider it a great value because of all of the uses. If it extends the operation of your engine, it’s worth the cost. Save money on expensive engine repairs and replacements.

Pros

  • Fixes PowerStroke issues
  • Multiple functions
  • Friction modifier
  • Reduces engine noise

Cons

  • Expensive

5. Restore 00016

Value For Money Option

Weight/Capacity

16 ounces

Cleans Sludge?

No

Reduce Friction?

Yes

Chemical Composition

Petroleum

Key Feature

Fills in worn-out spots

Engine/Motor Oil Compatibility

Any, except PowerStroke

If you want to find the best oil additive for the money, Restore might have the product you are looking for. It restores cylinder compression, horsepower, and engine performance while reducing oil consumption. This high-performance option works great in older engines, including some types of diesel. The unique formula fills in worn-out areas of the cylinder walls to reduce blow-by. What you will experience is near original performance as a result.

As it improves the combustion, your vehicle gains horsepower, maximizes fuel economy, and hits peak performance. Plus, the pressure lubrication design protects components from wearing any further. Use this with your conventional or synthetic oil for a complete system. What this formula doesn’t have is special detergents to clean out the sludge.

Still, when you look at the reviews, you see that many customers have been thrilled with this product. In fact, it appears that it works almost immediately, so you will want to use it for quick results. Just don’t use it with a PowerStroke as the manufacturer warns against it. For the cost, you can afford to get a few bottles of this treatment versus just one of some of the other options. Think about what you can do with that savings.

Pros

  • Increases horsepower
  • Low cost
  • Immediate results
  • Reduces blow-by

Cons

  • Doesn’t clean

6. STP 15604B

Diesel Engine Option

Weight/Capacity

15 ounces

Cleans Sludge?

No

Reduce Friction?

Yes

Chemical Composition

Zinc

Key Feature

Contains zinc for older engine performance

Engine/Motor Oil Compatibility

Any

STP is a trusted brand when it comes to engine care, and this formula doesn’t disappoint. You might know the brand by the oils and other additives that are made, but this one is special. Older engines run best with a zinc-additive, and that's what this product has. You can rejuvenate the gaskets and seals to stop leaks fast. Plus, you should notice a reduction in smoking and noise after application. Use it in your cars, light trucks, or SUV for quick results.

Because the high-viscosity formula contains ZDDP, the anti-wear agent, you know that the metal-to-metal friction will be reduced. This additive supplies a thick cushion between all of the moving motor parts. This is available in a 15-ounce bottle and should be used with every oil change. In addition, the price is quite reasonable. You won’t have to spend a fortune to see results.

What we don’t see in this formula is a detergent to clean out the sludge and buildup. Still, increasing the performance and lubrication is enough to extend the life of your engine. With this included with your oil changes, you will take steps to drive your car, truck, or SUV for many more miles.

Pros

  • Includes ZDDP
  • Reduces smoking
  • Increases viscosity
  • Rejuvenates seals and gaskets

Cons

  • No cleaning agent

7. Bar's Leaks 4102

Budget Option For Older Engines

Weight/Capacity

16.9 ounces

Cleans Sludge?

Yes

Reduce Friction?

Yes

Chemical Composition

Petroleum

Key Feature

Removes sludge

Engine/Motor Oil Compatibility

Any

You will be hard-pressed to find an effective additive as low-cost as this option. Not only will it reduce friction and wear, but it also quiets noisy valves or lifters. Furthermore, this formula contains a detergent to prevent and remove sludge or buildup. You can put it in your engine anytime, and it can be used on any type of motor.

As it dissolves the sludge from the internal components, it creates more room for the oil to flow. Plus, this solution doesn't plug the oil passages as some others will. Regular use, with every oil change, will keep the deposits to a minimum. Use one bottle on your four to six-quart oil change. If you have a more extensive system, you will need one bottle per five quarts of oil. You can also double the amount for an overly dirty engine. Just pour in the double treatment, then change the oil and filter after driving 100 miles.

That’s how quickly this formula will work. You don’t have to spend a lot to get the results you want. In a few cases, this product didn’t produce any results, but it was rare. Plus, you won’t have to spend a lot to figure out if this is the solution for you.

Pros

  • Removes buildup
  • Low cost
  • Won’t plug oil passages
  • Can use more for dirty engines

Cons

  • Doesn’t always work

Chemical Compounds in Oil Additives

Zinc in some oil additives functions as a performance booster. It's ideal for older engines and often combined with phosphorus, which limits the metal-to-metal contact. Other formulas may include extreme pressure agents, magnesium sulfonates, nanoparticles, or other elements. Whatever option of chemical compounds you choose, make sure it receives the EPA certification.


Zinc Additives for Older Engines

Zinc additives are the best option for older engines, especially when combined with flat-tappet camshafts. With high zinc oil for older engines, you get a reduction of friction and minimal wear. The zinc is often shorthand for zinc dialkyl dithiophosphates or ZDDP. Modern oils don’t contain the zinc that older engines require, which is why you need an additive. On the other hand, zinc can hurt the catalytic converter and emissions. Zinc replacement additives offer some of the same lubrication without the potential downsides.


Tips to Making Your High Mileage Car Engine Last Longer

According to Consumer Reports, there are plenty of ways to extend the life of your car engine. Start by following the recommended maintenance schedule found in the owner’s manual. Don’t miss oil or spark plug changes. If a problem arises between the maintenance appointments, fix it immediately. Don’t allow the malfunctions to become more severe. When a repair is imminent, make sure you use high-quality parts and not low-cost knockoffs. It also helps to drive with care. Excessive braking and acceleration will wear out the car engine prematurely.


People Also Ask (FAQs)

How often do I need to change my oil additives?

It depends on the product you are using. Follow the recommended guidelines of the additive for the best results.

Is it necessary to change oil for my car? How often should I change engine oil?

You must change the oil in your vehicle at regular intervals to ensure exceptional performance. It was once industry-standard to change the oil every 3,000 miles, but most modern oils can go at least 5,000 miles now.

Will thicker oil damage my old car engine?

You should use the appropriate motor oil for your engine. Thicker viscosity oil creates a more considerable barrier between the metal parts but doesn't damage the older car engine.

Is synthetic oil good for older engines?

Synthetic oil flows smoothly but isn’t always good for an older engine. There’s a higher chance of excessive friction, which is why many manufacturers prefer using conventional oil with the older model motors.

Can oil additives improve oil pressure?

The majority of oil additives improve oil pressure, but only as a temporary fix.

Are oil additives the same as fuel additives?

While both oil additive and fuel additives can increase the performance and lower fuel consumption, they are added to the vehicle differently. Fuel additives get poured into the fuel tank while oil additives go into the engine with the oil.


Conclusion

What is the best oil additive for older engines? It depends on what your needs are, but we prefer Lucas Oil LUC10002 for most applications. Not only is it a great option as the best diesel oil additive for older high mileage diesel engines, but it also works with gasoline engines. You will find a lot of problems solved with this formula and just might notice your engine lasting longer.

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