The engine is the most important component in your car. If it fails, not only does your car not function, but it’ll be costly to repair. While routine maintenance and oil changes will keep your engine running in good shape, you’ll also want to consider using an engine flush from time to time. This way, your engine stays as clean as can be, helping to run for hundreds of thousands of miles.

So what exactly does engine flush do? To explain this, we take a look at LUBEGARD’s explanation for what’s going on when your engine is operating. A high quality oil filter is designed to remove contaminants up to 25 microns, but the most dangerous contaminants to your engine are between 5 to 20 microns. That means those contaminants are larger than the finest tolerances in your engine, but they’re also too small for your oil filter to remove. According to LUBEGARD, that causes approximately 60% of the wear on your engine. If you’re not flushing those harmful contaminants out from time to time, sludge, tar, varnish, and other wear metals can continue to circulate within your engine.

As a result, those contaminants will cause excess wear and tear on your engine, resulting in higher operating temperatures and reduced lubrication. If an engine becomes heavily contaminated, even an oil change isn’t sufficient to remove those contaminants. That’s where engine flushes come in—helping you flush all that sludge, tar, varnish, and other contaminants from your motor.

In addition, engine flushes are great to use after an extended interval in between oil changes, or if you just purchased a used vehicle and don’t know its service history.

For more information on the best engine flushes, refer to our table of contents.

1. Editor's Pick: LIQUI MOLY Pro-Line Engine Flush

liqui moly pro-line engine flush

This German company specializes in oils, lubricants, and additives, and its engine flush is one of the best on the market. It’s suitable for use on all gasoline and diesel engines with and without diesel particulate filter. Designed to clean the engine from the inside, this engine flush removes deposits from crucial engine components, reducing engine noise and oil consumption. It is tested safe for use with catalytic converters and turbochargers, and a 500ml bottle is enough for over 5 quarts (5 liters) of oil.

Like all engine flushes, it’s extremely simple to use: Simply add it to your engine oil at running temperature, before you change your oil. After pouring it into your engine, allow the engine to idle for 10 to 15 minutes. Afterwards, change the oil and the filter.

Product features:

  • Company specializes in oils, lubricants, and additives
  • Suitable on all gasoline and diesel engines
  • Cleans the engine from the inside
  • Reduces engine noise and oil consumption
  • Safe with catalytic converters and turbochargers

2. WYNN'S Engine Flush

wynn's engine flush

This recommendation is designed to clean all oil lubricating systems before you do an oil change and is a highly detergent concentrate. Working quickly to dissolve varnish, sludge, and other contaminants from vital engine parts, this engine flush will also leave behind residue that prevents the contamination of fresh oil. It neutralizes acids and will work to free sticking internal engine components by dissolving deposits.

You can use this engine flush with all gasoline and diesel engines and it’s compatible with all mineral, synthetic, single, and multigrade oils. To use it, simply add the engine flush to the engine oil prior to an oil change, while the engine is warm. Let it idle without load for about 20 minutes and then change the oil while your engine is still warm.

Product features:

  • Works quickly and efficiently to dissolve varnish, sludge, and other contaminants
  • Leaves behind residue to prevent contamination of fresh oil
  • Neutralizes acids
  • Frees sticking internal engine components
  • Works on all gasoline and diesel engines
  • Compatible with mineral, synthetic, single, and multigrade oils

3. Throttle Muscle Engine Scrub

throttle muscle engine scrub

This option is a super concentrated, premium crankcase cleaner. What sets this engine flush apart from the competition is that it features a special residue solubilizer and a high quality engine oil base, helping to efficiently remove sludge and harmful engine deposits. Like other engine flushes, it’s designed to restore your engine to a much cleaner state before you do an oil change.

For a complete engine flush, add this product to existing oil before an oil change. You’ll want to let the engine idle for about 5 minutes before draining your oil and replacing your oil filter. The company also suggests if you want a more complete service, drain your old oil and change the filter first, before adding the engine flush and additional oil to reach a minimum of 75% capacity. Then, run the engine for 5 minutes before draining out the oil, changing out your filter again, and filling with fresh oil.

Product features:

  • Super concentrated, premium cleaner
  • Features a special residue solubilizer and high quality engine oil base
  • Efficiently removes sludge and harmful engine deposits

4. LUBEGARD Engine Flush and Protect Pack

lubegard engine flush and protect pack

This premium synthetic blend contains special detergents and dispersants to clean gums, varnishes, and deposits from your engine. It also works to free sticky valves and lifters, while improving oil circulation. This recommendation does not contain any harmful solvents, so it won’t damage seals or gaskets in your engine. It can be used in all diesel and gasoline engines, and this package includes an engine oil protectant that protects and extends oil life by 30% by reducing engine temperatures and minimizing friction and wear.

The company recommends adding the engine flush and letting your engine idle 10 to 15 minutes prior to draining your oil and performing an oil change. Make sure the engine is warm before adding the flush.

Product features:

  • Premium synthetic blend
  • Contains special detergents and dispersants
  • Cleans gums, varnishes, and deposits
  • Frees sticky valves and lifters
  • Improves oil circulation
  • No harmful solvents—won’t damage gaskets or seals
  • Compatible with all diesel and gasoline engines
  • Includes engine oil protectant

5. STP High Mileage Engine Flush

stp high mileage engine flush

If you have a high mileage engine that is in desperate need of cleaning, this is the recommended option for you. This engine flush is specially engineered for vehicles over 75,000 miles, with super concentrated agents that actively clean deposits in the engine and a high quality base stock. It will work to help reduce sludge and varnish on cylinder heads, and it won’t harm your engine’s seals. Compatible with gasoline and diesel engines, conventional and synthetic motor oils, you’re safe to use this product with every oil change, when used as directed.

To use this product, let your engine reach normal operating temperature and then turn the engine off prior to pouring the bottle into your oil crankcase. Afterwards, turn the engine back on and let it idle for 5 to 15 minutes. Then, drain your oil and do your routine oil change.

Product features:

  • Designed for high mileage engines with over 75,000 miles
  • Super concentrated agents actively clean deposits
  • High quality base stock
  • Reduces sludge and varnish
  • Won’t harm engine seals
  • Works on gasoline and diesel engines
  • Compatible with conventional and synthetic motor oils
  • Can be used with every oil change, when used as directed

We are committed to finding, researching, and recommending the best products. We earn commissions from purchases you make using the retail links in our product reviews. Learn more about how this works.