Can you flush motor oil & auto fluids with a septic tank?
The short answer for motor oil & automotive fluids and a septic tank: never. Motor oil, antifreeze, and other automotive fluids are toxic, do not break down, and destroy the tank's bacteria while contaminating the soil and groundwater the drain field discharges to.
Take used motor oil and automotive fluids to an auto-parts store or hazardous-waste collection site.
- Verdict
- Never — they poison the tank and contaminate groundwater
- Why
- Motor oil, antifreeze, and other automotive fluids are toxic, do not break down, and destroy the tank's bacteria while contaminating the soil and groundwater the drain field discharges to.
- Take used motor oil and automotive fluids to an auto-parts store or hazardous-waste collection site.
When in doubt, throw it out — only the three Ps (pee, poo, toilet paper) belong in a septic system.
Check another — What are you thinking of flushing?
Use the Can I Flush This? Septic-Safe Lookup to check any other option, or jump straight to one of these:
Rather skip straight to quotes?
Send the short form — we'll route you to an independent local pro.