Is it Safe to Add 2-Stroke Oil to My Diesel Fuel?

Some diesel owners like to add a little 2-stroke oil to their fuel tank to lubricate the fuel system and upper end of the cylinders. Sometimes, people use regular motor oil, too. So, is it safe and effective to add 2-stroke oil to diesel fuel?

The fuel system needs lubrication

The fuel system and upper end of your engine require lubrication to resist wear and last as designed, which the diesel fuel is supposed to provide.

The waxes found in diesel fuel lubricate the fuel pump and injectors, helping fight wear. Without them, the highly engineered components in modern diesels, particularly high-pressure common-rail (HPCR) engines, can wear out or develop deposits that interfere with an optimum spray pattern, reducing power and fuel economy.

Reduced lubricity of ULSD

The problem, however, is that today’s ultra-low-sulfur diesel fuel (ULSD) provides significantly reduced lubricity – a critical property in controlling fuel-pump and injector wear.

The ASTM standard for diesel fuel, D975, controls a minimum level of lubricity. Unfortunately, it’s not as much as the Engine Manufacturers Association (EMA) would like.

Since 2006, nearly all diesel available in North America has been ULSD.

Why? Because the government mandated reduced sulfur to curb harmful emissions. ULSD contains a maximum of just 15 ppm sulfur, compared to up to 5,000 ppm some diesel fuel used to contain prior to EPA regulations. ULSD also is compatible with modern exhaust treatment devices, such as diesel particulate filters (DPF), that also help reduce emissions.

I doubt anyone will object to cleaner air. But ULSD can have the negative side-effect of reduced lubrication for diesel fuel pumps, injectors and the upper end of the engine. Since a full-blown injector replacement can cost thousands of dollars, some diesel enthusiasts add a little 2 stroke oil to the diesel fuel to replenish its lost lubricating properties as a precaution.

Is adding 2-stroke oil to diesel safe?

In general, yes, but it’s not recommended.

Instead, use a diesel fuel additive designed to keep the combustion chamber clean and lubricate the fuel system, like AMSOIL Diesel All-In-One or AMSOIL Diesel Injector Clean.

They work better and are far easier to use compared to metering out a few tablespoons of 2-stroke oil and finagling it into the fuel tank without making a mess.

They also provide several additional benefits that help keep your diesel running strong, including…

AMSOIL Diesel All-in-One

  • Cleans dirty injectors
  • Lubricates pumps and injectors to reduce wear
  • Extends fuel-filter life
  • Improves fuel economy up to 8%
  • Protects against injector wear better than Sea Foam, delivering 2X more diesel fuel lubricity¹
  • Combats fuel-system corrosion
  • Prevents wax settling during storage
  • Lowers cold filter-plugging point (CFPP) by up to 40ºF
  • Delivers maximum horsepower
  • Increases cetane up to 4 points
  • Safe for use in all diesel fuels, including biodiesel
  • Alcohol-free
AMSOIL Diesel All-in-One reduces diesel's CFPP
AMSOIL Diesel All-in-One

AMSOIL Diesel Injector Clean

  • Cleans dirty injectors
  • Lubricates pumps and injectors to reduce wear
  • Restores power and torque
  • Reduces smoke and emissions
  • Combats fuel-system corrosion
  • Reduces downtime and maintenance costs
  • Extends fuel-filter life
  • Improves fuel economy up to 8%
AMSOIL Diesel Injector Clean

I love the do-it-yourself independence of adding 2-stroke oil to diesel to solve the problem of insufficient diesel fuel lubrication. But it’s best to leave your chemistry set in the garage and use a diesel fuel additive formulated specifically for diesel fuel.

¹Based upon independent testing of AMSOIL All-In-One obtained Nov. 8, 2018 and Sea Foam Motor Treatment purchased on Oct. 25, 2018 in the ASTM D6079 test.


  1. I use Walmart brand 2 stroke, 1 Qt per every other fuel up.
    My 2004 F250 PSD runs clean, and still gets 17 to 18 mpg on the highway.
    I also use AMSOIL lubes in both my diesels, and I use AMSOIL fuel cetane additive.

    1. An old timer told me about this years ago. His business? He rebuilt diesel injection systems. Said Type F automatic transmission fluid is one of the best lubricant (and cleaner) for diesels…and it’s relatively inexpensive.

  2. When many engine makers were forced to adapt their engines to meet the EPA tier III emissions standards in mid Y2K when at the same time the petroleum industry was forced into coming out with ULSD when the debate was to use a dash of two stroke oil to the fuel tank to replenish the lubricity lost when traditional diesel fuel was to be used. As the ULSD claims to be compatible to the emission control devices on modern diesels when experts claim to recommend diesel fuel additives instead when there is a benefit of using the additives when they claim to provide anti-gel properties. As common rail engines could see the benefits of diesel fuel additives when owners could be forking over thousands for an injector replacement when in some cases the warranty would be sticky when the claim could be denied when technicians find traces of two stroke oil within the fuel system when owners claim to recover the lubricity lost of ULSD when there was a gallery of things that would be a warranty killer when owners are paying for the repair out of their own pocket.

  3. I have a question, so how much 2 cycle engine oil is safe to put in my 95 7.3 liter powerstroke? And what kind?

    1. Hi Josiah,

      We recommend against using two-stroke oil. Instead, use a diesel fuel additive specifically designed to lubricate the fuel system and provide cleaning properties. AMSOIL Diesel All-In-One is a great option.



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