Gasoline Engine Oil Grade Chart

Gasoline engine oil grades are classified according to SAE viscosity grades. There are six types of winter oils: 0W, 5W, 10W, 15W, 20W, and 25W. The "W" stands for winter. The smaller the number in front, the greater the oil circulation volume and the lower the usable temperature.

Summer oils come in five types: 20, 30, 40, 50, and 60. The larger the number, the higher the oil viscosity, the stronger the high-temperature maintenance characteristics, and the higher the natural temperature environment it can be used in.

There are 15 types of all-season oils: 5W20, 5W30, 5W40, 5W50, 10W20, 10W30, 10W40, 10W50, 15W30, 15W40, 15W50, 20W20, 20W30, 20W40, and 20W50.

API quality grades divide engine oils into S-series and C-series products. S-series products are designated for automotive gasoline engine oils, while C-series products are for diesel engine oils. When labeled with both S and C, it indicates that the oil is suitable for both diesel and gasoline engines. Products in each series are arranged numerically (A, B, C, D, E, F, etc.). The further the letter in the alphabet, the higher the grade and the stronger the characteristics.

Gasoline engine oil grades include SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN, and SP. Diesel engine oil grades are CA, CB, CC, CD, CD-II, CE, CF-II, CF-4, CG-4, CH-4, and CI-4.

The correct engine oil grade for your petrol car depends on factors like climate, engine type, and manufacturer recommendations. Most modern petrol engines use 5W-30 or 5W-40 synthetic oil, which offers good performance in varying temperatures. The grade (e.g., 5W-30) consists of two numbers: the first (5W) indicates cold-weather viscosity, while the second (30) refers to high-temperature performance.

1. 5W-30: Ideal for most UK climates, balancing cold starts and motorway driving. Used in popular models like the Ford Focus and Vauxhall Corsa.
2. 0W-20: Common in newer, fuel-efficient engines (e.g., Toyota hybrids), offering better cold-flow properties.
3. 10W-40: Often recommended for older or high-mileage engines, providing thicker protection at higher temperatures.

Always check your car’s manual or use an online lookup tool for the exact specification. Using the wrong grade can reduce efficiency or cause engine damage.

From a mechanic’s perspective, the oil grade chart is about matching viscosity to engine needs. Thinner oils (0W-20, 5W-30) flow better in cold starts, reducing wear. Thicker grades (10W-40) suit older engines with wider tolerances. For turbocharged petrol engines, synthetic 5W-40 is often best. Ignoring the chart risks poor lubrication or sludge buildup. Stick to the manufacturer’s recommendation—deviating voids warranties.