Short answer
API TC is an American Petroleum Institute classification for two-stroke engine oils, written for high-performance air-cooled engines such as motorcycles, snowmobiles and chainsaws, but not outboards. It is the only one of the four original API two-stroke classes still in use. Today many equipment makers also list JASO or ISO two-stroke grades, which are more recent.
The four original API two-stroke classes
API defined four two-stroke classes. TA was meant for very small engines, roughly under 50 cc, but its engine tests were never completed after European support for the category was withdrawn. TB was intended for scooters and small engines of roughly 50 to 200 cc and was later abandoned. TD covered water-cooled outboards; it was superseded when the outboard industry moved to its own NMMA program, which now calls for TC-W3.
That leaves TC, aimed at high-performance two-stroke engines typically in the 200 to 500 cc range, such as motorcycles and snowmobiles, plus chainsaws running lean fuel-oil ratios.
What an API TC claim tells you
TC describes an oil intended to control ring sticking, scuffing and deposits in air-cooled two-stroke engines. Unlike API’s gasoline and diesel engine oil categories, there is no API “donut” licensing mark for TC, so the claim rests on the marketer’s own testing and documentation.
Because the API classification has not been actively developed in many years, many equipment makers now name JASO M345 (FB, FC, FD) or ISO-L-EGB, EGC or EGD instead of, or in addition to, API TC.
API TC and outboards
API TC is not an outboard specification. Water-cooled two-stroke outboards run cooler combustion temperatures and are lubricated under different conditions, which is why outboard makers specify NMMA TC-W3. An oil can carry both API TC and TC-W3 claims if it has been developed for both, but each claim must stand on its own.
How to use it when choosing oil
Treat API TC as a minimum description, not a complete specification. Check the equipment manual for the grade it lists, which may be API TC, a JASO or ISO grade, or the engine maker’s own oil. Then follow the maker’s fuel-to-oil ratio, which is separate from the oil classification.
Frequently asked questions
Is API TC still valid?
API TC is the only API two-stroke class not withdrawn or superseded, and it still appears on many labels. Many manufacturers now also reference JASO M345 or ISO two-stroke grades.
Can I use API TC oil in my outboard?
Outboard makers generally call for NMMA TC-W3. Use the category in the outboard manual.
Is API TC the same as JASO FC?
No. They are separate classifications with different test programs. Some oils list both.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].