What happens if I miss a scheduled oil change?
The short answer is: bad things could happen if you miss a scheduled oil change! Just as you need good blood flow through your veins and arteries to stay healthy, your engine needs good, clean oil flowing through it to stay healthy and run well. Think of oil as part of the “circulatory system” of your vehicle.
Understanding Your Oil's “Circulatory System”
Changing your oil (and oil filter) regularly is very important and will help your engine live longer. Your engine has many moving parts and clean, well-circulating oil is needed for them to work efficiently.
Your engine oil performs three important jobs: to help clean, cool and lubricate many moving parts. And inside your engine, there are quite a few moving parts, all highly engineered to incredibly tight tolerances, and all having to work in harmony.
The clearance between the moving piston and the cylinder wall, as well as between the crankshaft, camshaft and piston connecting rods and their respective bearings, and all the other moving parts, is measured in thousandths of an inch. To put that in perspective, a typical strand of human hair has a diameter in the neighborhood of .004” – four thousandths of an inch. This means there's not much margin for error.
When the oil is operating as it should, these metal parts inside the engine don't actually touch one another as they do their job. Rather, they glide past one another on a microscopically thin film of oil. If parts do come into unintended metal-on-metal contact, they will wear faster or even become damaged.
While engine parts such as pistons and bearings may seem smooth and polished to the unaided eye, at a microscopic level they all have peaks and valleys. If, for example, the oil film thins and two metal parts begin to touch, the peaks will get sheared off and can work their way into the engine bearing material. The engineers call this asperity, but all we need to remember is that if this happens, it is very bad for the engine's longevity.
In addition to lubricating the moving parts by creating this thin film, oil also removes heat and cleans your engine. All engines become hot when they've been running, with the average temperature being between 195°F and 220°F. This means you definitely don't want to put your hand on an engine block that's been running recently.
And while keeping your engine cool is the primary job of your cooling system (which includes your radiator, thermostat, hoses and coolant), your motor oil also plays an important role. As oil circulates through the engine it absorbs and helps remove heat from the moving parts. If the engine overheats and runs hotter than intended, damage or premature wear to parts inside can occur.
But eventually, even the normal high engine temperatures take their toll and the oil and additives begin to break down and lose their effectiveness. Thinner oil means there is less lubrication in the engine to keep it cool and create that film of oil between the metal parts that are sliding past one another.
Oil collects dirt particles, contaminants and impurities from your engine. These then get collected in the oil filter. This is how oil cleans your engine. When your oil is drained and your old filter replaced
with a new filter, and fresh oil is added, the contaminants will have been removed from your engine.
But there is a limit to how much dirt and contaminants your oil and filter can hold. In the worst case — which usually means you waited way too long to get your oil changed — if your filter becomes full, the bypass valve opens. This means that while the oil will keep circulating in your engine, it's now completely bypassing the oil filter. This is another reason why it's important to change your oil (and filter) on the recommended schedule for your vehicle.
What is Sludge?
Another danger of not changing your oil often enough is sludge buildup. Sludge is created when old oil starts to solidify. It's caused by a combination of oxidation and contaminant build-up in a poorly maintained engine.
When sludge forms, the oil can't flow as easily as it should through the engine. Sludge can make it hard for oil to flow between the moving metal parts because it starts to clog some of the narrow oil passages. This can cause oil starvation to crankshafts, bearings, camshafts, and other important parts. Oil starvation means oil isn't getting where it's needed to do its job. Eventually this will lead to major engine damage. In short, sludge is bad, very bad.
What is Oxidation?
Oxidation is a chemical reaction that happens when oil is exposed to oxygen. Think of how a cut-up apple will turn brown; that's oxidation from the apple reacting with the oxygen in the air. Oxidation happens inside engines too, and happens even faster if the oil is exposed to water or very high temperatures.
Oxidation also happens where it's extremely cold, because the oil can become diluted with water. When this happens, the oil doesn't flow as well.
Oxidation breaks down your engine oil quicker and — like sludge — is bad for your engine. When oil oxidizes:
- It wears out faster
- It thickens and won't flow as well
- It can eventually turn to sludge
All of this technical jargon aside, oxidation is a chemical reaction that happens to oil and it is very bad. It causes the oil to be less effective in doing its job of cooling, cleaning and lubricating.
What are oil Additives?
Engineers add a variety of chemical additives to oil to make it work better. In fact, about 20% of every quart of oil is made up of these additives. Additives are really important, as they can help minimize corrosion and sludge build-up. They can even lessen the likelihood of oil leaks on higher-mileage engines.
Each oil manufacturer keeps their precise formula secret but typical additives include:
- Detergents to help keep engines clean
- Antioxidants to help prevent rust and corrosion
- Viscosity modifiers to help keep the oil at the right thickness at higher temperatures
- Dispersants to help lessen the likelihood of sludge forming
- Seal swell additives to help minimize oil leaks in higher-mileage engines
- Anti-foam agents to help prevent oil foaming and keep the oil lubricating as it should
- Corrosion inhibitors to help protect metal parts from rusting
- Anti-wear agents to help prevent the moving metal parts from wearing out
If nothing else, what's important to take away from this is that additives are very important, and all additives will break down over time and stop being effective. That's yet another major reason why it's important to change your oil according to the manufacturer's recommended schedule.
Metal, dirt, and other impurities will build up in your oil. And, eventually the additives in your oil will break down and weaken the protection for your engine. Over time, even the best oil will lose its lubricating and cleaning abilities. This will make your engine run less efficiently and shorten its life. If you don't change your oil and oil filter frequently enough, the filter will stop working, leading to faster, more severe wear inside your engine. Eventually it will lead to engine failure and expensive repair bills.
Get to know your suggested maintenance schedule and bring your vehicle to the Ford to the techs who know it best.