Walk into any oil shop and the shelves are full of numbers and letters: 20W-40, 5W-30, SN, SP, CI-4. This guide explains how to read them, and which kinds of grade different vehicles typically use. It is written for vehicle owners, workshop mechanics and small fleet operators.
Rule one: the owner's manual decides
The engine maker tested the engine with a particular oil grade and specification. It is printed in the owner's manual, and sometimes on the filler cap or a service sticker. Use that grade first. Everything below helps you understand the label; it does not replace the manual.
How to read an engine oil label
Every engine oil label tells you three things: the viscosity grade, the performance category and the type of base oil.
Viscosity grade, for example 20W-40
The SAE number tells you how thick the oil is. The first number, followed by W (for winter), shows how easily the oil flows when the engine is cold. A lower number flows more easily at a cold start. The second number shows how thick the oil stays at normal running temperature. A higher second number means a thicker oil when hot.
Performance category, for example SN, SP or CI-4
The API letters show the service category. S is for petrol engines and C is for diesel engines. The second letter moves forward through the alphabet as newer tests are introduced, so SP is newer than SN, and CI-4 is newer than CF-4. A newer category can usually be used where an older one is asked for, but check the manual to be sure.
Base oil: mineral, semi-synthetic or fully synthetic
Mineral oil is refined from crude oil and is the most economical choice. It suits simpler engines and shorter change intervals. Semi-synthetic oil, also called a synthetic blend, mixes mineral and synthetic base oils. Fully synthetic oil is engineered for steadier performance in heat and at cold starts, and is typically used with longer change intervals. Some modern engines specify it. If your manual asks for a type, follow it.
What different vehicles typically use
Motorcycles and scooters (4-stroke)
Common grades are 10W-30, 10W-40, 20W-40 and 20W-50, with API SN or SP on newer bikes. Most motorcycles share one oil between the engine and the wet clutch, so the manual often asks for a JASO MA or MA2 rating. Check that the product datasheet lists it before you buy. In the Lukeron range, SPL 4-STROKE comes in 20W-40, 10W-40, 10W-30 and 20W-50, and ECO 4T UNI is the economy option.
Cars and SUVs (petrol)
Modern engines often specify thin grades such as 5W-30 or 0W-20 with API SP. Older engines in hot climates are often run on 20W-40 or 20W-50. Cars running on CNG work hot, so some oils are made specifically for them. The Lukeron SPL PCMO range covers 5W-30 and 0W-20 in semi-synthetic and fully synthetic types, and 20W-50 for CNG.
Trucks, buses and commercial vehicles (diesel)
15W-40 is the common grade, with API CI-4 or CF-4 depending on the age and emissions standard of the engine. Heavy loads, dust and long hours shorten oil life, so use the shorter interval the manual gives for heavy-duty work. Lukeron SPL HDEO is 15W-40 API CI-4 PLUS, and ECO Engine Oil is the economy grade.
Tractors and farm machinery
20W-40 oils of the CF-4 type are commonly used. Farm engines idle for long periods and work in dust, so service intervals are normally counted in running hours as well as months. Lukeron SPL Agri Engine Oil is 20W-40 CF-4.
Does a thicker oil protect better?
Not necessarily. An oil thicker than the engine was designed for can make cold starts harder and can flow less freely through the narrow passages of a modern engine. An oil thinner than specified in a worn engine can lead to higher oil use. Use the grade the manual gives, and ask a mechanic before changing it for a worn engine.
How often should you change it?
It depends on the engine, the type of oil and how the vehicle is driven. Follow the interval in the manual, and shorten it for severe use such as dusty roads, heavy loads and stop-start traffic. Each Lukeron product page shows the recommended change interval for that product.
A quick checklist before you buy
- Open the manual and note the viscosity grade and the API category.
- Check whether the manual asks for semi-synthetic or fully synthetic oil.
- For a motorcycle, check the JASO rating on the datasheet.
- Choose the pack size that matches the oil capacity, so you do not store half-used containers.
- Keep the container sealed and out of direct sunlight until you use it.
Need help choosing?
Tell us the vehicle or machine and the grade written in the manual, and we will suggest the matching Lukeron product. You can also use the engine oil finder in the Tools section of this website. Always follow the grade and specification in the owner's manual.