Why some cars use more oil

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If you notice smoke coming from the tailpipe, it’s perhaps because your car engine is consuming too much oil. Excessive oil consumption is something all car owners dread, but ironically it’s while they do something motor related that they realise their oil levels is low and needs to be topped up.

And this usually happens only if the oil change is done by professionals and not the owner as most owners assume that excessive oil consumption is the oil’s fault. However, there are many more reasons why some cars use more oil.

  1. The most common and apparent reason is a leak, which should be addressed first. You know that your engine’s oiling system lubricates essential moving parts and some of these elements like the rings and valve guides prevent the oil from entering the combustion chamber. However, once these parts wear out, it leads to a gap between the mating surfaces and this makes it easy for the oil to enter the combustion chamber where it ends up burnt and emits smoke through the tailpipe.
  2. The engine design also determines your car’s oil consumption as engines of some makes and models use more oil from day one. So if oil consumption is crucial to you, it’s better to check the forums about different cars to find out what other owners have to say about their car’s oil consumption.
  3. The condition of your engine’s seal and gasket also affects oil consumption. It’s because the more worn out they are, the more oil the engine consumes. So if you have a high mileage new engine, and there were previously no oil consumption problems, this is the most probable reason for your car using more oil as it grows old. This is related to a leak as the oil finds a way around the seals to end up burning in the combustion chamber or leaks out.
  4. Hot car engines lead to thinner engine oil. And it’s so much easier for thin oil to reach the combustion chamber to mix and get burnt with fuel.
  5. Did you know that your driving style also affects oil consumption? Yes, the higher is you’re RPM, the more oil that ends up getting consumed. This is because higher RPMs place extra pressure on seals and gaskets and once again, the oil finds its way around and is burnt in the combustion chamber.
  6. Even the quality of oil you use for your engine affects the oil consumption levels. It’s the low-quality oils that are highly volatile and has an impact on the oil consumption rate.

Too-low viscosity oils are not suitable for your engine. So if the oil has both low HTHS and SAE viscosity levels, then your car will consume and use engine oil much faster. Now you know the reasons for increased oil consumption, here’s how you can diagnose and assess the situation. You have to run the engine for a few minutes while idling, and then turn off the engine and let it sit for a few minutes. Now restart the engine and observe the exhaust as you immediately increase engine speed.

If there is a massive billow of smoke which disappears, and you have a relatively clean exhaust, then excessive valve guide wear is most probably the cause of increased oil consumption, which needs servicing. However, if there is only mild smoke which remains consistent under all working conditions, then the piston rings need testing. This can be done by a ‘dry’ and ‘wet’ test where the dry test is performed with a compression tester in the spark plug hole to measure the engine’s compression after disabling the ignition system. The engine is then cranked, and the pressure measured and recorded.

The wet test comprises of pouring a few teaspoons of oil into the spark plug hole and measuring the compression again. If there is an increase of more than 15 PSI, then it means the rings are worn out, and you may have to perform significant engine servicing. While compression testers are found in most auto parts stores, do follow the manufacturer’s instructions for proper usage. Also, make sure the ignition system is disabled to prevent possible engine starting.

Now that you have diagnosed the condition, there are a few things you can and cannot to about your engine’s increased oil consumption.

  • First and foremost, it’s not advisable to immediately start high viscosity oils just to fight oil consumption. There are some things to consider like high viscosity oils also lead to worse cold temperature performance, increased oil pressure, poor oil circulation, minimal heat transfer, and if the engine has thin oil passages, the oil lubricates very poorly even in operating temperatures.
  • While this does not imply that lower viscosity motor oil is a better choice, it just means that you should maintain and follow the range specified by your car manufacturer. However do not use thicker oil than permissible to reduce oil consumption as though you can place grease in the engine instead of oil, though there will be no oil consumption, your engine fails in a matter of minutes or seconds! This proves that an absence of oil consumption does not mean better engine lubrication or longer engine life.
  • While a stop leak additive may help reduce oil consumption, it’s only a temporary solution. Instead of treating the cause of the increased oil consumption it just hides it.
  • You could consider switching oils and starting using fully synthetic oil if you haven’t used such oils so far. This is because synthetic oils come with lower volatility, and does impact your engine’s oil consumption rate.
  • You can also try changing your driving style wherein you maintain a steady 2-2.5k RPM most of the time. Not only does this help save your oil, but it also helps save your fuel costs too.

If you still don’t know why some cars use more oil, it’s time you consulted a mechanic for help instead of doing something wrong. You may end up spending more money, and doing more harm than good to your engine!

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