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Regency Generators Knowledge Base

Why use oil in my diesel generators engine? What different kinds of oil are available?

Why use oil in my diesel generators engine?

Oil in your diesel generators engine is essential. It lubricates all the moving parts when running, reducing wear and prevents the diesel engine from seizing. It also helps to cool down some parts and it may help to inhibit corrosion when unused for short periods.

What different kinds of oil are available?

Oil is typically available in mineral, semi-synthetic and fully synthetic types. Your engine manufacturer will recommend which type of oil to use in your engine. More modern engines typically require synthetic oil, while older designs use mineral oil. So what is the difference? What about the grades? What does 10W-40 viscosity number mean?

Mineral Oil

Mineral oils are made from crude oil which naturally occurs in the earths crust. It is refined and processed to produce different products. Waxes and other impurities are removed in an oil refinery. Mineral oils are usually at the thicker grades of engine oils.

Fully Synthetic Oil

Fully synthetic oil is just that - it is fully synthesized and designed to meet the exacting demands of modern engines. This process makes them more expensive to buy, because they cost more to produce. So why pay this premium? Because each is tailor-made to provide the best performance, excellent engine protection and great fuel economy. They are also more stable at high temperatures and fluid at very low temperatures. Synthetic oils are around twice the price of standard mineral oil.

Semi-Synthetic Oil

As the name implies, this is a mixture of both mineral and synthetic oil. This mixture produces a mid range product, cheaper than synthetic, but better performance than mineral oil.

What about the viscosity number? What does it mean?

The number you see on engine oil is important - it is called the viscosity and refers to how well a liquid resists flowing. You can imagine water flowing easily down an inclined pipe whereas something like whipped cream wouldn't  flow quickly at all.

In a diesel engine, this is a little more complicated - because the engine might be hot, or cold. The oil needs therefore to be able to flow in both these situations. The higher the number, the more it resists thinning. So for engine oil there are two numbers. For example, 10W-30. The first, with the W shows how much the oil will resist thinning at 0 degrees F (about -18 degrees C). The W stands for Winter - when its usually cold! The lower the number here, the less it thickens in the cold.

The second number shows how the oil performs when it is hot at 212 degrees F, (100 degrees C). The lower the number the more the oil will thin out at high temperatures, so 10W-30 will thin out quicker than 10W-40 if its hot.

Engine manufacturers normally recommend a grade of oil based not only on their engine, but also recommend a different viscosity based on the expected temperatures.