How often should I change my engine oil? I remember my first job in a garage as a young man, that was back in the days when you would take your car to the garage at least twice a year to change the engine oil and have a service. It varied a bit depending on manufacturer, but about every 5000 to 6000 miles was the norm.
In those days the garage would have just one barrel of oil in the corner of the workshop and every car would get a dose of the same oil, either 20w/50, or a few years later, 15w/40. This was a mineral oil and had to be changed frequently to maintain it’s integrity. Things have come on a long way since then, but not necessarily for the better.
In that same workshop, today, there has to be a multitude of different kinds of oil to suit some very particular engines. 5W-30 is probably the most common grade of oil you will find in a modern workshop, but there can be 7 or 8 variants of that oil, depending on the demands of the vehicle’s engine.
The latest specification for engine oil in some Japanese makes is 0W-8, which is like sewing machine oil! The main driving factor for this is ever tightening government legislation to have zero emissions and a clean atmosphere. Unfortunately, this means that engine manufacturers have to find ways to meet those specifications. In some instances this means developing engines with tighter internal tolerances to maximise efficiency. These tighter tolerances mean less space for a film of oil to flow between the engine components to prevent wear. So, that leads to an oil that has super low viscosity. An oil with a lower viscosity also improves friction between the surfaces of engine components like the crankshaft, which in turn improves fuel efficiency.
Lower-viscosity oils reduce internal friction since they flow more easily than higher-viscosity oils, improving fuel economy. With fuel-economy standards growing more strict, auto-makers are leaning toward low-viscosity lubricants to help them meet the requirements.
It’s also important to note that the use of the ‘wrong’ variant of oil can cause huge problems with modern car engines. For example, if you do not use the correct ‘LOW SAPS’ version of the recommended oil grade for your diesel vehicle, you will cause the DPF filter to block up prematurely, which could lead to total breakdown and a large repair bill.
**Note to self: Stop buying cheap 10W-40 ‘top-up’ oil from Tesco every time I go shopping!**
Let’s take a look at those numbers and find out what they mean.
The numbers associated with the oil you put in your engine refer to oil viscosity, which is a measure of the oils resistance to flow. A 5W-30 oil exhibits good flow characteristics in both winter cold and summer heat. In other words, at -35°F, the oil will retain its ability to flow and will refrain from gelling. The oil will also retain its ability to flow and protect an engine at high temperatures (212°F). These are the test points used by SAE, which you may also see on the label.
The SAE’s testing program centres on a viscosity number of 30. The 5W-30 identifies the oil as a multi-grade oil that, at -35°F retains the characteristics of a 30 weight oil. The W identifies the oil as Winter grade oil (it will flow in the cold, which is great for the UK). The 30 identifies it as a 30-weight oil that will flow at high temperature. SAE standards apply to not only multi-grade oils, but also single-grade oils well.
This brings us back to the initial question.......
How often should I change my engine oil?
With the advent of fully synthetic oils the rules changed a lot. It’s now not uncommon for the engine oil to be changed at 10,000 or even 20,000 miles.
Some vehicles even monitor the condition of the engine oil dynamically and tell you when it needs changing. Whilst it is important to follow the manufacturers recommendations, it’s also important to take into account other external factors that prematurely degrade your engine oil. Thus, reducing the lifespan of your car’s engine, and that’s what most people ignore until it’s too late.
Some of these include:
- Towing a trailer or carrying goods on a roof rack.
- Frequent fast acceleration then stopping/slowing considerably shortly afterwards.
- Regular short trips of less than 5 miles under normal conditions or 10 miles in freezing conditions.
- Frequent start/stop driving in hot weather.
- Frequent driving on roads that are dusty, muddy or have salt or gravel on the surface.
- Driving at less than 50mph over long distances
It’s also worth noting that short slow trips cause quicker degradation of oil quality than driving long distances on a motorway at the speed limit, so may result in more frequent oil changes being necessary.
It’s important to monitor the overall quality of your engine oil on a regular basis. Whilst driving style and conditions play a part on the lifespan of your engine oil, there are other factors at work that have an impact on your engine oil, its lifespan, and the subsequent longevity of your vehicles engine.
The increased use of biodiesel and ethanol based fuels leaves sludge, varnish and lacquer deposits within your engine. Also the fitment of Exhaust Gas Recirculation (EGR) and after treatment systems (DPF/SCR) leads to increased ‘soot loading’ of the engine oil. If these contaminants are left to accumulate, they inevitably lead to premature engine failure.
You’ll have noticed that I haven’t managed to answer the question, how often should I change my engine oil? For the simple fact that there are so many variables these days. There really is no such thing as a ‘one size fits all solution’.
But, what I can tell you is this. Change your engine oil as often as possible, while maintaining a little common sense about it. Manufacturers schedules must be taken as absolute maximum times. The vehicles we see in our workshop that have critical engine problems, are usually those that are serviced minimally and infrequently.
As a rule of thumb, most modern vehicle engines will benefit from having their oil flushed, the oil filter replaced and new engine oil added at least once a year, or every 10,000 miles at the most. Even if the vehicle manufacturer says it is too soon!
It always pays dividends to form a relationship with a garage like Liphook Auto Services who’ll give you up front honest pricing, you’ll get the job done right, and you won’t end up with a repair bill you need to speak to your bank manager about! As members of the Good Garage Scheme, we also follow their ‘Industry Standard Service Plan’ which ensures consistency across all Good Garage Scheme members, and gives the customer the confidence that their vehicle has been serviced to the highest standard.