Does Motor Oil Expire?

If you change your own oil, the chances are you’ve got some old engine oil on your shelf. Likely it’s nothing more than an opened 1-liter top-up bottle, or an unused 4-liter bottle. You then wonder, "Does motor oil expire?"




WHAT DO THE OIL COMPANIES SAY?

There is a general consensus of terminology coming from the oil companies that unused, unopened, and stored in its original container out of extremes of temperature, motor oil will last for an “extended period”. They then go on to suggest that the oil shouldn’t be used after a few years; the exact period varying between 2 years (according to Total) up to 5 years (Mobil).

So while motor oil manufacturers say we should responsibly dispose of oil after a few years they all stop short of saying that the oil does actually expire. Clearly, there is a vested interest in their future sales here so, to get to the truth about oil, you need to drill down deeper.

WHY DO WE NEED MOTOR OIL?

The primary purpose of motor oil is for lubrication. Inside the internal combustion engine, hard metal surfaces slide backward and forwards across each other at high speed and at very high temperatures. The oil forms a fluid barrier between the moving parts, lowering friction and, crucially, reducing wear on major engine components like pistons, connecting rods, crankshaft, and of course the cylinder linings of the block itself.

Secondly, the oil also acts as a coolant, drawing heat away from the engine as it circulates, and third, it keeps the engine clean by carrying away dirt and debris from high wear areas.

HOW DOES MOTOR OIL EXPIRE?

The manufacturers’ advice on storage gives some clues as to what might happen to degrade the oil. Extremes of temperature can affect oil in different ways. Too hot and thermal breakdown occurs reducing the oil's viscosity (its “weight” or thickness), which, if used, leads to a decreased flow rate and in turn to increased oil consumption, the build-up of deposits, and potential damage to engine surfaces. Too cold and sludge will form in the oil, blocking engine oil passages and eventually becoming too thick to flow at all.

Another possible degradation cause is oxidation, more likely with a container that’s been opened, which is when the oil molecules react with oxygen molecules in the air. In this instance, viscosity increases forming sludge and sediment. Oxidizing oil can also increase acidity and start to rust or corrode any metal surfaces it contacts.

An opened, partly used container also renders the oil more susceptible to contamination from water condensation or dirt, both of which reduce its effectiveness as a lubricant.

DOES THE TYPE OF OIL MAKE A DIFFERENCE TO WHETHER IT EXPIRES?

Simply put, yes- the type of oil matters a lot. The key to this is whether the oil is synthetic and what additive ingredients there are. Both conventional and synthetic oil began life coming out of the ground, but synthetic oil is further refined, distilled, purified, and broken down to a basic molecular level. From this point, the oil’s molecular structure can be rebuilt and customized to suit a specific purpose, such as the greater demands of heat tolerance in modern engines.

Even though this more uniformly engineered base oil is already an improvement over conventional oils, it is further improved through a blend of additive compounds. These extra ingredients counter the typical breakdown causes by maintaining viscosity at extremes of temperature through detergents and dispersants which delay sludge build-up, isolating contaminants by suspending them in the oil, and counteracting the effects of oxidation.



WHAT ABOUT OIL INSIDE AN ENGINE, WHAT HAPPENS THERE?

Everything that could happen to break down oil in a container, is even more likely in use inside an engine. It is subjected to much higher temperatures and, of course, mechanical action. As conventional oils in use start to break down straight away, the maximum recommended driving between oil changes used to be only a few thousand miles. Depending on whether you drive hard miles- characterized by lots of short trips where the engine oil barely warms up- or easy miles, such as longer highway journeys – your engine oil can last a full-service interval for 10,000 miles or more.

The biggest issue in use now is contamination. As the oil circulates around the engine it picks up dirt such as soot and microscopic slivers of metal worn away from the moving parts. This is beneficial in that it takes the dirt away from the engine, but even with a good oil filter (like a Wix) it can eventually become saturated with debris and start to form a sludge.




WHAT IS RECOMMENDED?

Only use the type and grade of motor oil recommended by the car’s manufacturer. For example, Dodge recommends Pennzoil Ultra Platinum Full Synthetic 0W-40 for the 6.4 Hemi. Make sure the oil and filter are changed according to the mileage intervals given in the owner’s manual, or if the car has sat unused for more than a few months.

While premium brand, fully synthetic motor, oils are expensive and you might be reluctant to waste them, the cost is trivial compared to having major surgery on your engine to replace worn components caused by filling up or topping off with degraded oil.

So, does motor oil expire? Yes, it can but depending on the conditions and the type of oil it might take a long time. You are okay if the expiration date on the container is still good, or you know exactly how long you’ve had it and how it has been stored (i.e., a cool, dry location away from sunlight).

MOTOR OIL – HOW DANGEROUS IS IT?

Used oil cannot just be put out with the trash or poured down the drain. Used oil is classified as a highly toxic, hazardous chemical. Clean oil is relatively safe but once it is used in an engine and is no longer clean, it becomes a carcinogen. Pennzoil says, "Used oils may contain harmful impurities that have accumulated during use. The concentration of such impurities will depend on use and they may present risks to health and the environment on disposal. All used oil should be handled with caution and skin contact avoided as far as possible." (Note- Continuous contact with used engine oils has caused skin cancer in animal tests).

Bearing this in mind it is important to use good practice when you store, handle, or dispose of used oil. This also explains why dumping oil in a landfill is illegal in many parts of the world and can lead to a hefty fine- in short, the initial time and effort saved by dumping it is not worth it.

MOTOR OIL DISPOSAL – THE EASIEST WAY TO COLLECT IT?

When changing your motor oil, it is advised that a trash bag is put underneath the pan– that way, the majority of the oil can be collected in an easily transportable way with minimal effort. If any oil is spilled it can be easy to clean up if you know what you’re doing. Pouring cat litter or sawdust over any spill will help to absorb the puddle before it stains anything. After letting it soak up for a couple of hours, sweep the pile up and secure it in a bin bag– be sure to wear gloves and wash your hands thoroughly after finishing.

To ensure that the ground underneath remains free from stains a squirt of dishwashing soap and a brief scrub with a hard bristle brush will do the trick.

Unpainted concrete may be trickier to clean effectively so instead mix a 50:50 solution of laundry detergent and bleach, pour it on, and wipe up the residue with paper towels. Once again, use gloves and wash your hands afterwards.

MOTOR OIL DISPOSAL– STORING IT FOR TRANSPORT?

One simple way to efficiently collect and safely store the oil is to use a plastic bottle, such as the one it came in, or an old water bottle. A storage unit that can be sealed leak-free is recommended.

The easiest way to get the oil from the bin bag, as mentioned earlier, is to place a funnel in the neck of the bottle, hold the bin bag over it, and puncture a hole in the bottom. This will minimize spillage while allowing you to collect the oil easily. You may want to put down some paper towels to soak up any spilled drops.



WASTE MOTOR OIL – WHERE TO TAKE IT?

Motor can be taken to a recycling plant if it’s clean, however, if it is dirty and contaminated, as is more likely the case, it must be taken to a local waste disposal center.

Many auto shops and garages also accept oil that they will safely dispose of. Check on Google for those in your area.

The recycling or disposal site will then be legally responsible for disposing of the oil and your work is done!