What’s what with oils?
QWe need oil for a petrol generator and the markings on oil containers are confusing. The recommended oil seems to be AP1, SE, SF, SG, SH, 10.30, but all we can find locally is a semi-synthetic ACEA A3/B3 API, SL, CF. Would it be okay?
There are two parts to the way oil is designated, one relates to its viscosity or ‘runniness’ and is a standard set by the Society of Automobile Engineers ( SAE). The higher the number, the less ‘runny’ or more viscous the oil.
By the 1960s mono-grade oils ( SAE 20, SAE 30 and so on) could no longer provide optimum lubrication, so multigrades were developed. These have two viscosity numbers separated by a W so we get SAE 20W50 or SAE 15W40. The first letter shows how ‘runny’ the oil is when cold and the second when it is hot. The oil does not get thicker, it just thins more slowly as it heats up than a mono-grade oil. So it looks as if you need an SAE 10W30.
The second part is a set of performance standards. There are two standards bodies, ACEA ( European Automobile Manufacturers’ Association) and API (the American Petroleum Institute). API has a logical progression system. The first letter tells you what engine type the oil is designed for so, if the two or three character designation starts with an S, it’s for Spark ignition (petrol) engines. If it starts with a C, it’s for Compression ignition (diesel) engines. Some oil
Ameets the criteria for both engines so you find API specs starting with both S and C. If the oil is for your boat you concentrate on the Cs and if it’s for a petrol generator, concentrate on the Ss.
What follows the initial letter is another letter or sometimes a letter and number that defines the performance standard. The further up the alphabet the letter the higher/better the oil performs. Nowadays, pure mineral oil simply cannot perform well enough for some engines and has to be produced in a factory, so oils for high performance engines tend to be known as fully synthetic or synthetic.
Oils for more modest engines are based on mineral oil but have chemicals added to meet performance standards. These are lsemi-synthetic.
So, you are looking for an SAE 10W30 oil in API SE, SF, SG, or SH. The oil you quote would appear to be of a too high specification for your generator but, being a petrol engine, I doubt it will do much harm apart from to your wallet. You also do not give its SAE (viscosity) designation. Doing a Google search shows most 10W30 oils are expensive synthetic oils. If you do not want to get it mail order and have no time to visit outlets such as Countrywide Farmer’s Stores and Motor Factors, I suspect the best you can do is to use a 10W40 in API SE, SF, SG, or SH oil. This will be the correct viscosity when cold but a bit thicker than that specified