Have you ever seen that movie Colors?
Well, it's not about the different colors of engine oil and what it means. But thankfully, if you're looking for answers to why the oil in your dirt bike or ATV is milky or white, you found the right place. For the movie about an experienced cop and his rookie partner who patrol the streets of East Los Angeles while trying to keep the gang violence under control, you found the wrong place.
In many respects, oil is the lifeblood of all gasoline or diesel powered motorized machines. Dirt bikes and ATVs, certainly no exception. If you cut yourself and your blood bleeds anything but crimson red, you'd likely freak out and call a doctor. The color of blood should be red; likewise the color of oil should be amber or dark brown. If it's anything else - depending on the color - change it or call a mechanic (and yes you can be the mechanic).
Hopefully you check the oil regularly. Keeping the engine oil in your dirt bike or ATV fresh and at optimum full levels goes a long way towards the immediate performance and long term sustainability of the motor. So the next time you check the oil and you see something other than normal, ordinary amber colored oil you've got problems.
Black oil simply means it's doing its job. Oil is supposed to collect and trap dirt and other contaminants preventing engine breakdown and abnormal wear and tear. Black oil means it's loaded with contaminants, losing its viscosity and at this point requires changing. Keep in mind that some bikes, after just one ride, turn the engine oil a very dark brown to almost black. It's important to know your bike well so you're not unnecessarily changing the oil prematurely and racking up maintenance bills.
It's about time the engine oil gets changed!
But if the oil is near or has exceeded the hours threshold recommended by the manufacturer and appears black as night - change the oil and filter.
If you've never seen milky oil it's a bit alarming. Milky oil looks a bit like coffee with creamer. Sometimes, it's also frothy like a milk shake. Milky oil means water contamination from either coolant or moisture in the system. Most likely, it's a coolant problem and since coolant is petrol based it generally mixes well with engine oil but not in a good way.
Coolant and engine oil enjoy a hot and heavy date when the cooling circuit mixes with the lubrication circuit via defect or damage to one or the other. For example, a bad head gasket allows coolant to seep out of the cooling jackets of the cylinder and seep into the combustion chamber, other times a water jacket cracks or breaks allowing coolant into the engine. Alternatively, a failed water pump seal allows the two fluids to mix.
If it's not coolant and all checks out with the radiator and other applicable seals then someone is sabotaging your ride and putting water directly into the engine. OK, probably not, though not unheard of, but more likely from moisture build-up as a result of not properly storing your dirt bike over the long term. Condensation floats to the bottom as oil rests on top and when you fire up your dirt bike the water and oil mix creating a milky situation.
In severe cases, milky oil looks more like gelatinized bacon grease which means you've discovered a barn find or you've totally neglected your ride because you let it sit for a really long time in its own oily filth or haven't changed the oil in 50,000 miles.
Silver or Gold Oil
If the oil is silver, i.e. looks like the liquid metal shapeshifting T-1000 from Terminator 2, you've got serious problems and not because it's going to magically extract from the engine and transform into a dagger. And if it's gold don't think you've found the mother lode. Metal shavings turn the oil a silver or gold color which occurs after breaking in a new engine, normal wear and tear or a failed bearing, for example.
A bad crank rod thrust washer on a 2009 Honda CRF450R left the oil filter covered in gold glitter
When breaking in a new dirt bike or ATV engine it's recommended to change the oil and filter after an initial short ride because of the tiny metal shavings produced. Healthy engines also emit small amounts of metal shavings showing why you should regularly change the oil and filter. Also, copper or bronze thrust washers often create a gold metallic shine to oil and lubrication systems with shared clutch and engine oil reveals gold tinted clutch fiber debris. Perfectly normal.
However, if heavy metal saturates your oil and not the airwaves in your garage then you've got a failed bearing or a bad crank rod thrust washer or something along those lines allowing excessive friction inside the crankcase.
Now you know why regular routine maintenance is so crucial. Not only does it prevent bad breakdowns from happening you'll often catch issues early before serious, detrimental problems turn costly.
For more oily information check out: