Car Running Rough After Oil Change? Two Vital Checks

It can be worrying after an oil change – or having one done at the car shop – to find that your car is now running rough, especially at idle. You may even be experiencing the whole car shaking in severe cases.

You’ve done the right thing by getting your car serviced and maintained properly, but you are left with another problem you didn’t have before.

Below we will highlight the causes of why your car is running rough and what you need to do to put it right.

Have you put too much oil in your car, or, more rarely, have you put an oil viscosity in your car that is inappropriate for the engine. Both can cause long-term damage to your engine unless you take action.

3 Quick Checks If Your Car Runs Rough After An Oil Change

Engine Oil Overfilled

Many people top off the oil level without doing a full oil change. Often people fixate on ensuring they have enough oil inside the engine but don’t realize that overfilling it can cause as much damage.

An engine overfilled with oil can cause a buildup of pressure. All liquids expand when they are heated, and oil is no different. Giving your oil less room to expand inside the engine can cause a pressure buildup that can damage valves and pistons and cause oil leaks as the oil escapes due to increased pressure in the engine.

An overfilled engine often triggers warning lights -even at idle – on the dash of a car but not always.

In severely overfilled cases, the oil pressure sensor will send an error code to the car’s computer (The ECU), but if you have only topped up your engine slightly above the max, this may not occur.

Another symptom of overfilled oil is an excess of smoke from the exhaust. It is usually black, and is the engine trying to burn off the excess oil.

It’s easy to check the oil level of your car. You need to ensure you are doing this on a level surface and that the engine has been turned off for 30 minutes.

Remove the dipstick, clean it, reinsert, take it out and inspect it. It should be below the max level. If it is above the level, drain the excess oil away.

There are two ways to do this.

Remove the oil filter and drain oil from there, OR
Remove the drain result in the engine sump and drain oil from there.

Wrong Oil Viscosity

More rarely, your car idles rough because you have the wrong oil viscosity inside the engine. Many oil types are available, ranging from mineral to semi-synthetic to fully synthetic – that have longer expiry dates-, and each type has various viscosity (thickness).

Each car manufacturer stipulates what oil should be used in their vehicles. Some people ignore this, especially in older cars, but damage can be caused. Sometimes the wrong oil can prematurely make the oil turn black very quickly.

Bear in mind if your car is under warranty, putting the wrong oil in it could negate a claim for any damage caused to the engine.

In truth, the oil inside your engine would have to be totally unsuitable for any rough idling to be that noticeable.

Check the manufacturer’s handbook or go online and check what engine oil should be used for your vehicle and then compare it with a disused and empty bottle you have used to top up or do an oil change with.

Engine oil is not there just to lubricate the engine but also to take heat away from it too. Overheating sometimes occurs with unsuitable oil, which is very rare.

You should drain it completely and top it up with the correct oil if it’s unsuitable.

It would be a good idea to flush through the engine to remove all traces of the bad oil before refilling with oil.

Using Expired Oil

Many people have old oil bottles on shelves, and the temptation is to save money on buying new oil and reusing the oil in half-full bottles.

Does Synthetic Oil Expire and Go Bad? [ANSWERED FULLY]

Caution is the word here. If you have topped up with oil from an opened bottle or even an old sealed bottle, it may have separated – think milk and cream – and not fit for purpose. If this oil finds its way into the engine, it won’t be capable of doing the job it is designed for

In reality, you should be able to trust a reputable garage or car shop to do this job for you correctly. If you have doubts about the trustworthiness or competence of the person who changed your oil, it may be best to get another oil change.

Unfortunately, no home check will show if your oil is bad unless precision equipment that isn’t available to me and you is used.

Will An Oil Change Stop Rough Idle?

Some people change the oil in the hope that it’s made stop the car from idling rough, but as discussed, oil normally has little to do with it.

If your car is still running rough after an oil change, these are the other causes.

Generally, it will be because there is a disruption in the balance of fuel and oxygen inside the engine. Luckily this is normally caused by a filter that isn’t doing its job correctly and is clogged.

The two main filters to check are the air filter. A clogged air filter can restrict the air entering the engine’s combustion chamber.

The fuel filter, when clogged, can restrict the flow of petrol or diesel into the engine slightly. However, the main cause on the fuel side of things is that the fuel injectors may be blocked.

Fuel injectors spray fuel into the combustion chamber, mixing it with the right amount of oxygen to create the spark to fire the engine.

These are the three main reasons for an erratic idle, but this article below goes into other courses in more detail and may be worth reading.

Many visitors read this article next: Erratic Idle Causes And How To Fix Them

In Conclusion

Your car may be running rough after an oil change, especially at idle, because either the engine has been overfilled with oil or the wrong type of oil was used in the oil change.