Does it Matter What Type of Oil You Put in Your Lawn Mower?

Time and Temperature

• Mowers that operate in temperate climes may function well with an oil rated at straight 30W. The viscosity of the oil remains at a constant value despite engine operating temperature. The constant and relatively heavy oil weight may also aid in slowing slight oil consumption that some older engines may exhibit. Hard starting may result, though, at temperatures below 40 degrees Fahrenheit.

Wider Ranges

• Multi-viscosity oils can provide essential lubrication in a wider range of temperatures, due to the adaptability of the oil weight. 10W-30 weight oil can gain viscosity as the temperature rises, with the added benefit of being somewhat thinner when cool. Cold starts are easier and protection increases as the heat climbs. The operating temperature range of a mower with 10W-30 engine oil is anywhere between 0 and 100 degrees Fahrenheit.

Synthetic Oils

• Synthetic engine oils can provide superior lubrication at a wider temperature range. The viscosity of synthetic oils responds more readily and is capable at weights below that of conventional oils. A 5W-30 synthetic oil can travel to the outer extremes of the engine at a cold start, affording proper lubrication when it is needed most. The operating temperature range for a mower with synthetic 5W-30 engine oil is between -20 degrees and 120 degrees Fahrenheit.

Two Strokes

• Some small engines are of the two-stroke design, and they require oil added to the fuel for top-engine lubrication. Many different brands exist with additives intended for specific purposes. The engine manufacturers often recommend a specific brand, or brands with the correct additives for the particular make of engine. This instance is one where "good enough" might very well not be good at all. Follow the manufacturer's recommendations anytime doubt exists.