locked engine in lexus es300 on 1994 Lexus ES300

why did the engine lock that had a full tank of oil

2 answers
Sometimes if the Fuel pressure Regulator goes out, it dumps fuel into the oil causing it to vapor lock.. has nothing to do with the oil other than gas being in it.... once you change the fuel Pressure Regualator and an oil change, should be fine .. or it could be just the starter locked up which then in that case you need a new starter.. we just did that on ours..
Could be that something broke in the engine. Or even with the oil full if the oil pump went bad no oil pressure could cause an engine to "lock up" Probably half a dozen more things too.