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It can be frustrating to have paid for or completed an oil change yourself only to see the oil black soon after. You may doubt the car shop did a good job or that you messed up.

First, we need to determine if your engine is a diesel engine or a gasoline engine.

If it is a diesel engine, it is more normal for the oil to turn black quickly but it’s not typical, though, with a gasoline engine.

We will explore the five reasons why your engine oil is still black and the quickest and simplest ways to fix it.

The old car engine oil wasn’t emptied fully and the engine flushed before new oil was put in, or the oil filter wasn’t changed. Empty the old oil, flush and then refill with new oil.

Let’s look at those two causes and the other three in a little more detail.

1. Could Need Additional Flushing Out

Some of the old oil could still be in the mix, making it appear darker. A good mechanic should properly flush out the old oil, but sometimes it can linger, or this step is forgotten altogether.

This problem will solve itself as the old oil is burned.

If you specified you wanted a flush and paid for one but have black oil, go back to the car shop and query why your oil is black. The engine flush liquid is cheap and costs around $5 retail so even less for a bulk buyer such as a car shop.

The next time you change your oil, it would make sense to get a flush of the engine to remove all traces of the old oil. The less often the oil is changed, the more likely it is to become sludge and the more difficult it becomes to remove it.


Free! There is nothing to do except wait. As mentioned, you could go back to the car shop if you paid for the system to be flushed before the new oil was put in.

2. You Waited Too Long Between Oil Changes

If you don’t regularly change your oil, dirt and sludge can build up in the engine and immediately turn the new oil black.

You should change your oil regularly, every 5000 to 7,500 miles so that this doesn’t happen. Your car needs to have clean oil to run correctly, and it will help extend the lifespan of your vehicle. It’s a false economy to cut back on oil changes.

Some minor damage may have already been done to your engine if you haven’t changed the oil regularly. Look out for metal shavings within the oil on the dipstick.

This is a sure sign that the oil has not been lubricating the pistons, and friction has caused damage to the engine.

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Depending on your area, an oil and filter change will cost you between $35 and $75 if you go to a mechanic, less if you are handy and can do it yourself. 

However, if you’ve seen shavings in your oil, this can be very expensive in both parts and labor to repair. 

3. Your Oil Is Mixing With Unburned Gasoline

If your engine is not running properly, it could mix unburned gasoline with your new clean oil. 

This is something you want to be diagnosed and fixed quickly as it can lead to more extensive and expensive issues especially if you see white smoke coming from the exhaust. The easiest way to tell if this is your problem is to smell gasoline while you are driving. If this is the case, then you will most likely need a new fuel injector. 

This isn’t a problem that will go away on its own, so you should take your vehicle to the professionals as soon as possible.


This is the priciest problem you can run into with black oil. Replacing your fuel injector will cost between $800 and $1400 for new fuel injectors and labor.

4. The Oil Filter Wasn’t Changed

Your oil filter should be changed every time you change your oil. If this is not done, the oil won’t remain clean and do its job.

If you know the oil was changed and flushed, it suggests that the filter was not changed out. The oil picks up dirt from the engine, and it needs a clean filter to run through to pick up and collect any impurities.

Changing the oil without also changing the filter is only doing half the job, and you are wasting the new oil.

It isn’t unsafe to drive your car before changing the oil filter, but you want to do it sooner rather than later.

Unfortunately, the oil filter is difficult to see from above as it usually sits at the bottom of the oil pan. If you decide to replace it have a look for any metal shavings within it as this shows signs of engine damage that is perpetuated by a poor engine maintenance schedule.


A new oil filter costs around $15, depending on the make and model of the car. Expect to pay $50 for labor, but this should have been changed as part of the oil change.

5. The Oil Wasn’t Changed At All

Most mechanics are honest and hardworking people, but you can get scammed just like in any industry. If you have ruled out everything else and you didn’t witness the oil being changed, it may be that it wasn’t. 

Take it back to the same shop and ask them to change it again while you watch. If you do not trust the mechanic you first went to, it may be better to take it to a new shop altogether.

If you took your car to the mechanic just for an oil change, this is unlikely to be a cause, but if you took it there for a major tune-up or service, they may have cut corners and not changed the oil.

Check brake, transmission fluid, and wiper windscreen fluid as these should have been topped up as part of the service you paid for.  

You can still drive your vehicle in this case, but you want to get it back to the mechanic as soon as possible.


If you take it back to the original mechanic, they should change it again for no additional charge.

Diesel Engine Oil Is Black After An Oil Change

Diesel oil contains soot from the combustion process and some of these particles are too small to get caught by the filter. It’s a common trait of diesel engines to have more carbon in them and shouldn’t cause you too much concern.

The EGR valve makes no difference one way or the other as diesel engine oil was tuning black quickly before they were invented.

New diesel engine oil will turn black quicker than petrol engines. As long as it’s smooth and non-sludgy then there is no need to worry.

In Summary

Black oil indicates that the engine wasn’t flushed before new oil was added or that the oil filter wasn’t changed.

Oil is a crucial player in helping get us where we need to go, so changing it regularly will ensure you are running on clean oil and your engine is adequately protected.

If it is a more severe issue like needing a new fuel injector or witnessing shavings in the oil, you will want to be sure to get that looked at promptly.

As a last note, it is always essential to go to a shop where you trust the mechanic and feel like they have your best interest in mind. 

You’ll need to be there at least every six months, so finding a mechanic that you like is a top priority.

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