There are various categories for separating gasoline and diesel oils. The most famous of these categories is the American Petroleum Institute (API), which categorized oils based on their quality in gasoline and diesel categories, in this category the petrol-based oils, abbreviated as "S" Which stands for SERVICE or spark ignition, and the lowest level of quality in this classification with SA and the highest quality is up to date with SN. Diesel engine oils are also marked with the letter "C", which is the commercial or compression ignition It is noted that the lowest quality level in this category is with CA and the highest quality to date with the CJ-4.  You can refer to the manual for choosing a suitable oil for your car, as the car manufacturer will offer you the best possible option based on the year of engine design and operating conditions. It is usually seen in the car's manuals that a specific oil is introduced and the driver avoids replacing other oils. Knowing this is that you can use other oils as long as the quality of the other oils you are looking for is identical with the oil that is introduced in the booklet or from a higher quality level that can be introduced to the quality level. Cover. For example, on the packaging of oils, read the API SG / CD and wonder which one, SG for gasoline cars or CDs for diesel cars! No worries, the additive of these types of oils is designed to be usable in both types of vehicles, and if you have a gasoline car that should use oil with a quality SG, you can use it and for diesel vehicles Similarly, in order to determine the appropriate viscosity, the same should be done. Again, the best way to determine the viscosity of the oil used in the vehicle is to look at the vehicle. The American Society of Automotive Engineers (SAE) (Society of AutomotiveEngineers) has outlined the viscosity of oils. For example, the SAE20W50 shows a certain viscosity and varies with SAE 10W40, SAE 5W30 or SAE 40, each of which indicates a certain viscosity. If you do not have access to the car manual, refer to automotive or lubrication experts.