This can be quite the rabbit hole. For starters, two-stroke oil is like religion: people believe their particular oil is the best because, well, either they’ve been told or they’ve been using that oil and their engine hasn’t seized. Thankfully, there are better ways to choose. Cheap oil can have drawbacks.

Note that 2T means for 2-stroke engines and 4T is, you guessed it, for 4-strokes.

There are two primary standards, American Petroleum Institute’s TC-3, and the Japanese JASO which was developed for high performance motorbikes. So if you’re going to mind a standard, use JASO. The most common version of TC-3 seems to be the trademarked TC-W3 for marine applications (search NMMA  2-stroke oil).

JASO standards are ranked like this:

  • Increasing quality is indicated by FA, FB, FC, and FD specifications where the higher values are better, mostly in detergent properties.
  • These rate lubricating ability, cleanliness, smoke potential, and a few physical properties.
  • ISO and JASO are essentially the same with a few minor differences.
  • The idea is to have independent tests validate claims by oil makers.

Other Specifications for Two-Stroke Oil

  • NMMA TC-W3 – two-cycle water-cooled, third generation. TC-W3 obsoletes TC-W & TC-WII. Oils with this spec do not use metal-based additives and are ashless. This is an outboard specific spec.
  • API TC – only API spec established for two-cycle engines. It regulates lubricity, detergency, ash content & pre-ignition. Oils with this spec are typically using metal-based, ash-producing additives.
  • JASO FA – original spec established regulating lubricity, detergency, initial torque, exhaust smoke, and exhaust system blocking.
  • JASO FB – increased lubricity, detergency, exhaust smoke, and exhaust system blocking requirements over FA.
  • JASO FC – lubricity and initial torque requirements the same as FB, however far higher detergency, exhaust smoke, and exhaust system blocking requirements over FB.
  • JASO FD – same as FC with far higher detergency requirement.
  • ISO-L-EGB – same tests and requirements as JASO FB.
  • ISO-L-EGC – same tests and slightly higher detergency requirements (piston varnish) as JASO FC.
  • ISO-L-EGD – same tests and requirements as JASO FD.