The phrase "oil drain" refers to the process of removing or draining out used or old oil from a machine or vehicle, so that it can be replaced with fresh oil for optimal performance and maintenance. Full definition
It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under severe conditions, e.g. extended oil drain intervals according to the manufacturer's recommendations. (mechanics.stackexchange.com)
It is recommended for highly rated diesel engines meeting Euro I, Euro II, Euro III, Euro IV and Euro V emission requirements and running under very severe conditions, e.g. significantly extended oil drain intervals according to the manufacturer's recommendations. (mechanics.stackexchange.com)
Working vehicles for many years but have not seen this engine oil drain out red before. (humblemechanic.com)