5 Common Oil Change Mistakes and How to Avoid Them

Changing your own motor oil is a classic automotive maintenance task that can save you money and give you a greater connection to your vehicle. However, what seems like a simple job is filled with small pitfalls that can lead to costly, and in some cases catastrophic, engine damage. A simple mistake can turn a routine service into a multi-thousand-dollar repair bill. For any car owner, whether you're a seasoned DIYer or just considering your first oil change, understanding these common errors is essential. Avoiding them will ensure your engine remains healthy, efficient, and reliable for years to come.

Common Oil Change Mistakes to Avoid

1. Using the Wrong Type of Oil
This is the most frequent and potentially damaging mistake. Your car’s engine is a precision machine designed to operate with a specific type of motor oil, and using the wrong kind can lead to poor lubrication, increased friction, sludge buildup, and premature engine wear. The most critical factor is the oil's **viscosity**, indicated by a grade like "5W-30." The first number (5W) refers to its flow rate in cold temperatures (W for Winter), and the second number (30) refers to its thickness at the engine's normal operating temperature. Using an oil that is too thick can strain the oil pump and prevent it from reaching tight tolerances on startup, while an oil that is too thin won't provide an adequate protective film on hot components. Beyond viscosity, you must also use oil that meets the manufacturer's specific performance standard (e.g., API SP, ILSAC GF-6, or a brand-specific standard like GM's dexos1). Using an uncertified oil can void your powertrain warranty. Always consult your owner's manual; it is the definitive source for the exact oil your vehicle requires.


2. Not Changing the Oil Filter
Trying to save a few dollars by skipping an oil filter change is a classic case of being "penny wise and pound foolish." The oil filter's job is to trap abrasive particles, sludge, and metal shavings, keeping them from circulating through and damaging your engine's sensitive components. Over time, the filter's paper-like media becomes saturated and clogged. When this happens, a bypass valve inside the filter opens, allowing oil to flow around the filter media to prevent oil starvation. However, this means completely unfiltered, dirty oil is now circulating directly through the engine, accelerating wear on critical components like bearings, pistons, and camshafts. For the small cost of a new filter, it is an essential and non-negotiable step in every single oil change.

3. Over-Tightening the Drain Plug
This is a simple mistake of using too much force, but it can have disastrous consequences. The oil drain plug only needs to be snug enough to prevent leaks, which is why it uses a soft metal crush washer to create a seal. Most car oil pans are made of cast aluminum, which is a relatively soft metal. If you over-tighten the hardened steel drain plug, you can easily strip the threads in the oil pan. A stripped oil pan is a major repair that can cost hundreds of dollars, as the pan often has to be replaced entirely, a labor-intensive job. The correct procedure is to always use a new crush washer and tighten the plug with a torque wrench to the exact specification listed in your vehicle's service manual. If you don't have a torque wrench, a reliable rule of thumb is to tighten it by hand until it's fully seated, and then give it a final one-eighth to one-quarter turn with a wrench—no more.

4. Not Checking the Oil Level After Filling
After you've refilled the engine with fresh oil, you cannot assume you've added the correct amount. You must verify the level. After adding the manufacturer-specified amount of oil, start the engine and let it run for about 30-60 seconds. This circulates the new oil and completely fills the new oil filter. Then, turn the engine off and wait at least five minutes for the oil to settle back into the pan. Pull out the dipstick, wipe it clean, reinsert it fully, and then pull it out again to get an accurate reading. The oil level should be between the "MIN" and "MAX" marks. Both under-filling and over-filling are dangerous. Under-filling can cause oil starvation and catastrophic engine damage. Over-filling can cause the spinning crankshaft to whip the oil into a foam, which doesn't lubricate properly, and can also lead to high oil pressure that can damage engine seals and gaskets.

5. Forgetting to Put the Oil Cap Back On
It may sound obvious, but in the process of cleaning up, it's surprisingly easy to forget to screw the oil filler cap back on. This simple oversight can create a huge mess and a dangerous situation. Without the cap, hot oil will splash out of the engine as you drive, covering your engine bay in a slippery, flammable mess. If this oil drips onto the hot exhaust manifold, it can easily start an engine fire. Beyond the mess, the oil cap is a critical part of the engine's Positive Crankcase Ventilation (PCV) system. Leaving it off creates a massive vacuum leak, which will disrupt the air-fuel mixture, causing the engine to run poorly, stall, and trigger a "Check Engine" light. Always make it a habit to double-check that the oil cap is back on and tightened securely before you even close the hood.

Mistake Potential Consequence The Correct Procedure
Using Wrong Oil Poor lubrication, sludge buildup, voided warranty, engine damage. Consult the owner's manual for the exact viscosity grade and oil specification.
Skipping Filter Change Dirty oil bypasses the filter, accelerating wear on internal engine parts. Replace the oil filter with a new, quality one during every oil change.
Over-Tightening Drain Plug Stripped threads in the oil pan, leading to a costly, labor-intensive repair. Use a new crush washer and a torque wrench to tighten to the manufacturer's spec.
Not Checking Final Level Under-filling causes oil starvation; over-filling can damage seals and foam the oil. Run the engine briefly, wait several minutes, then check the dipstick on level ground.
Forgetting Oil Cap Oil splashes out creating a mess and serious fire hazard; engine runs poorly. Make it the last thing you double-check before closing the hood.

Key Takeaways