Diesel Parts and Diesel Fuel Injection
Diesel Cold Weather Fuel And Additive FAQ
Cold Weather Diesel Fuel and Diesel Additive FAQs

Q.  I left a bottle of Stanadyne Performance Formula in my truck overnight and it froze solid, doesn’t that mean the product is defective?

A.  No.  It’s counterintuitive, but just like pure antifreeze, additive must be diluted to reduce its freezing temperature.  The reason for this is a phenomenon known as “freezing point depression.”  In order for a substance to freeze, the molecules of that substance must be aligned/ordered properly to form crystals.  If there are impurities in the substance (e.g. additive in solution with diesel fuel) the liquid is inherently less ordered and will not crystallize (freeze) as easily.  Conversely, when additive is unmixed, the molecules are uniformly distributed.  This means that the additive will freeze at higher temperatures than when it is in solution with another substance.


Q.  Can I use the additive after it thaws?

A.  Yes.  Freezing won’t reduce the effectiveness of the additive.  Bring the additive into a warm area and allow it time to thaw.  As a general rule, additives should be stored above 32° (F) to prevent them from freezing.


Q.  What’s the shelf life of Stanadyne additives?

A.  Stanadyne states that their additive products are good for several years, but if left undisturbed for a couple of years a slight separation may occur.  If this happens to bottles, just shake them a few times, if you have drums or five gallon cans, roll them around to remix the additive.


Q.  In severe cold, is Winter 1000 better to use than Performance Formula?

A.  A regular treatment rate of Performance Formula and then buffering it with an additional ¼ the recommended treatment of Winter 1000 works very well in severe cold.  Caution: blending too much additive can raise the pour point back up to that of the undiluted additive, due to over-saturation of additive in the fuel. 


Q.  What’s the difference between pour point and cloud point?

A.  The definitions below are from the SAE Automotive Fuels Handbook.  We included a definition of cold filter plugging point, a European term becoming more common in the US , that’s often used interchangeably with cloud point:

  • Pour Point – the lowest temperature at which a petroleum product will just flow when tested under standard conditions, as defined in ASTM D 97.
  • Cloud Point – the temperature at which a sample of a petroleum product just shows a cloud or haze of wax crystals when it is cooled under standard test conditions, as defined in ASTM D 2500.
  • Cold Filter Plugging Point (CFPP) – a measure of the ability of a diesel fuel to operate satisfactorily under cold weather conditions.  The test measures the lowest temperature at which wax separating out of a sample can stop or seriously reduce the flow of fuel through a standard filter under standard test conditions.


Q.     What’s the difference between a demulsifying additive and an emulsifying additive?

A.   Water in diesel fuel causes a wide range of problems for fuel systems, thus many users choose to additize fuel to protect against water contamination.  There are two main types of additive to address this issue:

  • A demulsifying additive (such as Stanadyne Performance formula) extracts water out of suspension with diesel fuel.  This allows the water to be separated from the fuel through the use of a water separator, ensuring that water is not passed through the fuel system.  General Motors specifies “Only alcohol free water demulsifiers should be used in General Motors diesel engines”.
  • An emulsifying additive works by surrounding water molecules with additive molecules, holding them in suspension.  Proponents of this type of additive assert that this allows the water to pass harmlessly through the fuel system.



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