Royal Purple® Max-Clean® is a state-of-the-art high performance fuel system cleaner that maximizes the performance of your fuel system. Max-Clean restores fuel economy by deeply penetrating deposits and cleaning injectors, carburetors, intake valves and combustion chambers.

The illustration below shows the before and after effects of switching to Max Clean.

Royal Purple Max-Clean is EPA / CARB Compliant. Recommended for use in gasoline and diesel engines and can be used with all ethanol blends or biofuel. Max-Clean can be used in both 4-cycle & 2-cycle engines and will not harm vehicle emissions equipment.

Max Clean Before and After


Multiple product fleet tests were conducted on various makes and models of vehicles. Royal Purple found that after as little as one treatment Max-Clean can:

  • Gas savings up to 6.1%
  • Lowers emissions up to 44%
  • Restores horsepower an average of 2.6%
  • Restore fuel economy an average of 5.5%
  • Prevents intake valve deposits at least 4X better vs. The nearest leading competitor to improve performance
  • Removes more than 68% of tough-to-remove combustion chamber deposits to improve performance and prevent damage to the engine
  • Reduce hydrocarbon, nox and CO emissions (on average 12%, 13% and 18% respectively)
  • Prevent rough idle, hesitation and stalling
  • Prevent premature spark plug fouling
  • Reduce deposit-related engine knocking and pinging

Royal Purple Max-Clean also stabilizes fuel during low-use and storage periods, preventing varnishing of fuel.


Pour entire contents of bottle into nearly empty tank immediately before refueling, then install fuel on top of additive. One (1) can treats up to 20 gallons. For tank sizes outside of this range, use one (1) ounce per gallon. In two-cycle engines, use one (1) ounce per gallon.


Max-Clean should be used every 10,000 miles or annually, whichever comes first.

Available Sizes

Available SizesPart NumberItem Number
6 x 20-Oz. Case11723300990175256
20-Oz. Bottle11722



PDS Max-Clean SDS Max-Clean

Independent Test Results

Intake Valve Deposits (IVD’s) are formed by oil slowly seeping past the intake valve guide seals and down the valve guides. When oil reaches the hot valve, it sticks and burns, forming black carbon deposits. They also result from unburned fuel vapors and oil vapors siphoning back into the intake manifold through the Positive Crankcase Ventilation (PCV) system. These stubborn deposits are very difficult to remove. As they accumulate, airflow into cylinders is restricted and causes loss of power and fuel economy. Max-Clean prevents IVD’s and optimizes performance.

*Testing performed 2020 by Southwest Research Institute.



Combustion Chamber Deposits (CCD’s) increase the compression ratio of an engine and the octane requirements of the fuel. If the fuel’s octane rating is not high enough to compensate for CCD buildup, it results in detonation and build-up of heat/hot-spots that damage head gaskets, piston rings and rod bearings. Knock sensors in modern engines detect detonation and trigger the ECU to retard timing. But this reduces performance and fuel economy, and increases emissions. Max-Clean removes CCD’s, relieves octane increase burden, and restores performance.

*Testing performed 2020 by ATD GmbH.



Depending on the nature and severity of IVD’s and CCD’s, they can reduce fuel economy by an average of 2%-7%, depending on engine type, driving conditions, and type/octane of fuel used. Max-Clean provides a one tank clean-up and is only required once every 10,000 miles of driving. The dollar savings that results from decreased fuel consumption between Max-Clean applications more than offsets its cost – meaning it actually pays for itself.

*Testing performed 2020 by ATD GmbH.



Oxidative stability of hydrocarbons in fuel impacts how quickly they chemically break down to form gums that stick to engine surfaces and coke (bake) into deposits. By delaying/preventing the onset of oxidation, less gums are formed, resulting in fewer deposits. This reduces the clean-up burden of fuel detergents. In this way, fuel stabilizers function synergistically with detergents to maintain total engine cleanliness. Max-Clean stabilizes fuel (especially before/after idle periods) to prevent deposit-forming gums.

*Testing performed 2020 by Southwest Research Institute.


Proof of Performance

Not sure which Royal Purple product is right for you?

This chart helps explain the differences so you can make the optimal choice for your vehicle maintenance.

Proof of Performance

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