This means that getting the right oil for your car is more important than ever. Get it wrong and while you won’t see instant disaster as you would if you’d put diesel in a petrol car, you will subject your engine to excess component wear.
“You won’t see an issue immediately. It’s not like putting contaminated fuel into your vehicle,” says Wright. “But within 20,000 miles, you could have severe operational issues.”
What kind of oil you need depends on the engine. All new cars will come with a recommended grade listed in the manual and usually a recommended manufacturer, too. The grade will be shown in numbers, separated by the letter ‘w’ – for example, 5w40.
“Put simply, the viscosity of an oil gives you an indication of its resistance to flow at given temperatures,” Wright explains. “The ‘w’ rating, preceded by a number, gives you an indication of how the oil flows at winter temperatures and the last number indicates flow in summer temperatures.”
However, the viscosity alone isn’t enough to indicate how well an oil will protect your engine. There are numerous tests that car manufacturers go through to formulate engine oils and these are ratified by an organisation called the European Automobile Manufacturers Association, known as the ACEA (an acronym of the organisation’s French title). The ACEA determines the exact requirements needed to meet the demands of different types of modern engine. The specifications, known as ACEA Oil Sequences, are renewed every four years but are backwards compatible for older vehicles.
“The high costs of investment in engine oil technology run into six or even seven figures for a set of engine tests. Oil blenders, manufacturers and marketers have to be certain that the lubricants they sell are suitable for a given application,” Wright says.
Each ACEA specification is denoted by a letter, followed by a number, which identifies the class of oil and a category within that class – for example, ACEA C3. This specification will be indicated on the oil packaging and the car manufacturer's manual will again specify which you should go for.
But what if you can’t find the exact recommended oil? Wright says drivers should tread carefully, because using the wrong oil can cause damage to your car’s engine.
The problem is that the oil industry is self-certifying. The ACEA defines the specifications, but it’s up to the manufacturers to make sure that the products they put out meet them. A technical organisation called ATIAL spot-checks products of its members every few years, but largely it’s down to the industry to self-police. Some lesser known oil suppliers have been known to label their products as a certain specification but not meet the standards.
“Sometimes it distorts the marketplace if you get some less reputable new entrants into a market selling product below the cost price of other, more reputable blenders. That’s when you get some questions raised.
“If something looks too good to be true, then it probably is,” Wright says. “If you have been offered the latest specification, fully synthetic engine oil in the pub for £1 a litre, then it probably is too good to be true.”
To combat such products and to check the quality of products, the UKLA launched the Verification of Lubricant Specifications (VLS) service. Anyone can suggest a product for it to test, and if it’s found to be wanting, the UKLA will ask the marketer to quarantine or recall the product, and relabel or reformulate it. Wright says that since the VLS was launched in 2013, it has made a positive impact on the quality of lubricants sold in Britain.