In the world of Engine Oils, we love our acronyms don’t we? 15w40, SAE 80w-90, ACEA, SUTO 10w-30, API … so many letters and numbers to decipher!
Here, we hope to simplify it a little by looking at the basics of why we have so many different oil grades available and what the lower and upper numbers mean.
Hopefully, this will increase your confidence when choosing which oil is best for your engine.
Who’s behind the grading of oil specification and can you swap one engine oil brand for another safely?
With engine Oil lubricants being an essential part of smooth operational performance, bulk engine oil and lubricant suppliers such as OptimOil have long kept in step with engine development by refining their lubricant technology to meet ever stringent requirements. The alignment in oil specifications for the different engine types is enabled by the publication of sequences, or standards by Automobile engineering societies and trade bodies. Whilst there are several such bodies globally, including the SAE (Society of Automotive Engineers), the ACEA (European Automobile Manufacturers’ Association), JASO (Japanese Automotive Standards Organisation), and EMA (Truck & Engine Manufacturers Assoc) these share a lot of their testing procedures and aims.
One major difference between the global regions is climatic conditions, hence the popularity of Multi-Grade engine oil in weather-volatile temperate regions such as the UK. Another regional difference is environmental protection policies, with the UK and EU having arguably the highest requirements of engine oil specification.
Lubricating oil has to be at the correct viscosity inside the engine (or gear transmission) to prolong the life of your hardworking equipment, keep your fuel expenditure optimised and prevent falling foul of environmental protection regulations. Additives are blended in to achieve the best performance. However, its a balancing act as some of those that protect the engine’s lifetime can cause blocking of the DPF (Diesel Particulate Filter, an exhaust carbon soot capture device) which has led to the development of Low SAPS engine oil.
This is an important factor as oil has more viscosity (resistance to flow) at low temperatures and its viscosity naturally decreases (it thins) as it heats up. As 100 degrees centigrade is the peak operating temperature of most engines, and around 90% of engine wear occurs at (cold) start-up, oil technicians originally had to blend at a compromise between warmed-up engine temperature and average ambient air (starting) temperature. This is how we arrived at single-grade motor oils, which required an oil change every Spring and Autumn, often SAE30 to SAE10 and back again. Changing the oil to match the season meant the ‘summer’ oil performs (at a higher temperature) the same as the ‘winter’ oil does (at its lower temperature). However, as this single grade is a compromise between starting and operating temperatures, it rarely met most optimum performance.
Multi Grade oil has been engineered to perform well over a wide operating temperature range, so it protects a cold starting engine from the first turn; right through to peak operating temp. Amongst all the engine oil lubricant suppliers near me, I’ve only ever seen multi-grade engine oils in their stock. However, single-grade and tight tolerance grades of Hydraulic oil, Gear oils and Transmission oil are available from OptimOil; these applications do not involve such temperature extremes as engines and so are blended to meet the correct specification required based on a smaller operating temperature range.
No, these numbers are the oil’s grade or rating given to an oil blend after going through a number of tests. A set of cold tests are performed below freezing temperatures and another set conducted at over 100 degrees Celsius. This is to see how the oil performs on cold starts and at normal engine operating temperature.
So, if the oil industry hadn’t confused things enough with their letters and acronyms, they threw in another term – “weight”. When does ‘weight’ not mean what something weighs? When its used in by an oil supplier! The weight grade of an oil actually refers to its behaviour, in relation to its temperature. It includes viscosity, along with a few other attributes that the engine’s design requires.
If an oil’s viscosity is too high, it will not circulate around and in between the moving parts as it should, leading to excessive engine wear, poor fuel economy and the risk of an expensive engine seizure. Too low a viscosity and the oil will fail to provide enough lubrication for protection, or is likely to leak from the system.
In summary, the common standards around grading motor oil mean you can safely use any oil that matches the numbers recommended by your engine’s manufacturer. For example, a Mobil 10w40 can be mixed with a Rock oil 10w40 or OptimOil E7 heavy duty engine oil or, for newer engines the E9 4 stroke oil is likely ideal. What you should not mix or use is a different weight grade to what your engine has been designed around, especially so if the first number is higher or the second lower than your engine spec as this will mean the oil is too thick to move at the start-up phase, or too thin to lubricate at the operating temperature.
If you are a heavy user of industrial gear oil, lubricant, specialist oils, or buying bulk engine oil then why not give OptimOil a call or get in contact to see how you much time and money you can save on your lubricant supplier.