What is the difference between diesel engine oil and gasoline engine oil

From a mechanic’s perspective, the main difference lies in how they handle combustion byproducts. Diesel oil is built to cope with heavy soot and acidic compounds from diesel combustion, which is why it has extra detergents. Petrol oil doesn’t need as much cleaning power but must manage higher engine speeds smoothly. Using diesel oil in a petrol car might cause excessive deposits over time.

Diesel engine oil and gasoline engine oil are formulated differently to meet the specific demands of each engine type. Diesel oil contains higher levels of detergents and anti-wear additives because diesel engines produce more soot and operate under higher compression. Gasoline engine oil has lower additive concentrations but includes friction modifiers for better fuel efficiency.

Key differences:

1. Additive package – Diesel oil has more detergents to handle soot buildup, while petrol oil focuses on reducing friction.
2. Viscosity – Diesel oils often have higher viscosity to withstand extreme pressures.
3. API ratings – Diesel oils use "C" classifications (e.g., CK-4), whereas petrol oils use "S" (e.g., SN, SP).

Using the wrong oil can lead to poor lubrication, increased wear, or clogged filters. For example, a Ford Focus with a petrol engine requires oil meeting ACEA A/B standards, while a diesel Vauxhall Corsa needs ACEA C-rated oil. Always check your vehicle’s manual for the correct specification.

The differences between diesel engine oil and gasoline engine oil:

1. Different API classifications. Diesel engine oil classifications start with "C," while gasoline engine oil classifications start with "S";
2. Different combustion flame temperatures. Diesel engine oil burns at a flame temperature of 1800 degrees Celsius, whereas gasoline engine oil burns at 600 degrees Celsius;
3. Different oil viscosities. Diesel engines operate in harsher conditions, so diesel engine oil has higher viscosity.

Additional information: Engine oil functions include reducing friction and high temperatures, minimizing gas leakage, and preventing contamination from external sources. It protects against contact with water, air, acidic gases, and engine components; cushions pressure surges in engine cylinders; and cleans contaminants from component surfaces. Additives also differ, and prices vary accordingly.