Engine oil keeps the internal parts of the engine lubricated and working smoothly. Without it, the engine would seize up, requiring a costly repair or a new engine or new car altogether.
There are many reasons why an engine might be consuming oil at a fast rate. Some are common; some are rare, but it’s a problem not to be overlooked. There are also ways to mitigate it as an engine ages.
What is excessive when it comes to oil consumption?
Excessive oil consumption is the consumption or loss of oil at a rate that is faster than “normal.” What’s normal depends on the specific engine, as each one will have its own recommended change interval and may burn oil at different rates compared to other engines. According the James Dunst at bellperformance.com, an average rate is 1 quart every 1,500 miles, and this number can be less than 1,000 miles for performance vehicles. Manufacturers will have a common mileage number for consumption, which you can find in your owner’s manual. It’s important to know that this number can change depending on what oil is used.
What causes excessive oil consumption?
Age is a common factor when it comes to burning oil. As the engine ages, parts and seals can wear out from usage. Other factors, such as driving style, how often the oil is changed, and the type of oil used, can affect the wearing of these parts. There are even some models that are prone to it. Check out our list of worst offenders below. If you have one of these vehicles and are reading this article, it may not be a coincidence! Here are some common culprits of excessive oil consumption:
Gaskets prevent leaks by sealing parts together. When these wear and tear from age, oil can leak out, resulting in leakage on the ground or oil being burned off in the combustion chamber. This can be common with worn valve seals and valve guides, creating excessive blow-by in the combustion chamber, which, when the gases combine with oil, create pressure. Eventually oil seeps past the gaskets, such as the valve cover gasket or crankshaft seal. In this case, oil can also burn off in the combustion chamber. Gaskets such as the intake manifold’s can create vacuum leaks, and failed gaskets in the oil pan can create leakage.
According to Edmunds.com, DIYers or mechanics who are not aware of the recommended oil may use a different type. That can damage the engine and can void the powertrain warranty. Many manufacturers have created specific blends for certain engines, and not using these or a similar type can wear down internal parts, leading to higher oil consumption.
Worn Piston Rings
Piston rings keep oil from entering the combustion chamber. If the piston rings have worn to a degree that oil is escaping, the oil can be burned off or create carbon deposits, which can affect engine performance and/or fuel economy. Worn piston rings can also create blow-by, which is when gasses from the combustion chamber get into the crankcase. These gasses can mix with the oil, degrading it and leading to oil consumption.
Vacuum leaks can draw oil up into the intake. This can create carbon deposits and sludge that may restrict air flow.
As engines surpass 100,000 miles or more, more oil consumption is expected. With age, internal parts like valve guides, valve seals, and piston rings can wear out over time, which can increase oil consumption.
How a car is driven and how hard the engine works can also affect oil consumption. Lugging the engine (working the engine hard at low RPMS, for example accelerating to pass without downshifting) or driving at high RPMs often can make the engine work harder, burning oil and gasoline at a faster rate than usual.
Skipping Oil Change Intervals
Your owner’s manual will have the recommended oil change interval for your vehicle. Exceeding this interval means dirty oil will contaminate engine parts, wearing them down faster. Oil may also burn at the recommended interval, and an engine working harder with less oil can lead to increased consumption.
Vehicles Prone to Excessive Oil Consumption
Some vehicles are more prone to burning oil than others. Here’s a few that are known for oil consumption complaints:
- 2012-2013 Chevy Equinox
- 2007 Toyota Rav4
- 2007-2009 Toyota Camry
- 2003 Honda Accord
- 2008-2010 Honda Accord
- 2012 Honda Insight
- 2007 Chevy Suburban
- 2010 Toyota Prius
How do I test for increased oil consumption?
There are a few ways to test for excessive oil consumption. There are also some preventative measures you can take to mitigate the chances of it happening as an engine ages.
Check the Oil Regularly
Checking the engine oil every 500 miles is a good practice to get a read of how much oil an engine is consuming. You can check the oil by letting the engine warm up, and turning it off and letting it sit so the oil can collect at the bottom. Then remove the dipstick, clean it with a rag, and reinsert it. Remove the dipstick again to check the oil level. If the level reads near the add or low mark, add a quart, and if it reads halfway between the add and full mark, add ½ a quart. If you find yourself adding a quart every 500 miles, unless it’s been approved by the manufacturer, you most likely have an oil consumption issue.
This video will walk you through the basics of checking your oil if you are a little rusty.
Look for Blue Smoke Blowing Out the Exhaust
Blue smoke blowing out the exhaust is a sign of an oil and gas mixture burning. This means oil is entering the combustion chamber and is burning away.
Test with UV Leak Detection Dye
If you suspect a leak, oil dye and a UV light can help locate it. Simply add the dye to the oil and let the engine reach operating temperature and run for a bit. With the engine off, identify any areas of leakage with the UV light.
Perform a Compression Test
A compression test will require the removal of the spark plugs and a disabling of the fuel injectors and ignition coils. The process includes inserting the compression tester into a cylinder, cranking the engine, and taking a reading. The highest and lowest cylinder compression measurements should be within a range of 15% of each other.
Notice Build up in the Engine or Spark Plugs
Sometimes oil deposits and sludge can chalk up the engine. This is also possible with sludge collecting on the spark plugs or the bottom of the valves, which means oil is getting in the combustion chamber.
How Do I Prevent or Fix Oil Consumption?
While excessive oil consumption can be a costly and timely fix , sometimes there is an easier fix, such as the PCV valve or oil pan gasket. In the case of internal engine parts, like piston rings, unless you’re an experienced DIYer, it may be best to leave this option to the mechanic. There are a few preventative measures you can take to lower the chance of facing excessive oil consumption as your engine ages.
Change Oil at Recommended Intervals
Following the manufacturers recommended intervals for oil changes can increase the life of the engine. It can also possibly stave off excessive engine oil consumption happening.
Perform Tune Ups
Typical tune ups give an opportunity to catch leaks in their early stages or before they happen, such as noticing grime on spark plugs or spotting worn seals. A tune up can also help increase engine life, and can even lead to early replacement of parts like the PCV valve before it becomes an issue.
Use High Mileage Motor Oil
As your engine ages, it can help to use a high mileage motor oil designed for older engines. James Dunst at bellperformance.com states that thinner oil such as 0w-20 is more likely to seep through the pistons. It may help to use a thicker oil if your manufacturer allows it. You can find the recommended oil in the owner’s manual.
Check For Leaks Regularly
As your car and engine ages, it’s good practice to check for leaks. Not only will this help spot oil leaks, but also other fluids like the transmission oil. To identify what kind of leak you may have, see our leak identification guide.