In general, a yellow-brown oily substance coming from underneath the washing machine usually indicates a major problem has occurred with your machine. Yet the only way to know for sure what kind of problem you're dealing with is to contact a washer repair specialist to have the machine serviced. A washing machine that's working properly won't leak oil, grease or water. Although some issues can be remedied with repair or replacement parts, typically the problem isn't worth the trouble or expense to fix when compared to the cost of replacing the washing machine.
The motor assembly operates the drum's belt or motor coupler that moves the drum during agitation and spin cycles. The motor assembly contains multiple parts that work together with the aid of oil to reduce friction. Over time, if the motor assembly malfunctions, it can ooze oil that deposits underneath the washing machine. Depending on the damage to the motor assembly, you might need to replace the entire component. Confirm that repair or replacement costs are covered under the washing machine's warranty before having the issue addressed.
If the motor assembly isn't leaking an oily substance, the transmission might be the culprit. Although appliance manufactures have modified the design of transmissions on washers produced after 1995 to prevent oil leaks, oil leaks can still occur on older models. If you have an older model washing machine, or discover oil underneath the washer, the transmission probably has worn. Contact a washer repair specialist to inspect the transmission. If the specialist indicates that the transmission is leaking, replace your washing machine and upgrade to a newer model that's less likely to leak oil as it ages.
A rusted metal drum can leak water into the cabinet and underneath the washing machine. Although oil won't be what's collected below the washer, the rust particles in the water might make the water appear yellow-brown and oil-like. Once a metal drum rusts, it can't be repaired. While you can replace a drum, replacing your washing machine is generally more economical.
Verify that the water inlet hoses at the back of the washing machine aren't leaking. While the water that leaks from the hoses generally won't be yellow-brown, if the water is coming from the hot water inlet hose, the water may be discolored. Hot water can deteriorate a rubber hose faster than cold water and cause the hot water hose to produce a yellow-brown oil-like substance, which will appear in the pooled water that has accumulated behind and below the washer. If you discover that either hose is damaged, replace it.