🔍 Key Concepts

• Ethylene glycol is commonly used for a specific purpose on board machinery systems • How engine lubricating oil can become contaminated by other fluids on the engine • Typical symptoms and causes of different types of lube oil contamination (coolant vs fuel vs dirt vs wear)

💭 Think About

• Ask yourself: In what system on the engine is ethylene glycol normally found, and how could that system communicate with the lube oil system? • Which type of contamination (coolant, fuel, air/dirt, or wear metals) would most likely introduce ethylene glycol specifically, not just generic impurities? • If piston rings were worn, what kind of contamination or change in the lube oil properties would you expect instead of ethylene glycol?

✅ Before You Answer

• Identify in which fluid on an engine ethylene glycol is normally an ingredient • Eliminate the choices that would cause different contaminants (like dirt, fuel, or metal particles) rather than ethylene glycol • Consider how a leak or failure in that ethylene-glycol-containing system could let it enter the lubricating oil circuit