Each engine is referred to by both its family designation, such as 1MZ-FE, and its production or serial number. The serial number can be important when ordering parts. Certain changes may have been made during production of the engine; different parts will be required if the engine was assembled before or after the change date. Generally, parts stores and dealers list this data in their catalogs, so have the engine number handy when you go.
It's a good idea to record the engine number while the vehicle is new. Jotting it inside the cover of the owner's manual or similar easy-to-find location will prevent having to scrape many years of grime off the engine when the number is finally needed.
The engine serial number consists of an engine series identification number, followed by a 6-digit production number.
On the 5S-FE engine series, the engine serial number is stamped on the left rear side of the engine block. The 1MZ-FE engine stamping is located in the middle of the front of the engine.