My Briggs & Stratton manual calls for SAE 30 weight. What is wrong with using a 10w-30? On my snow blower it says use a multi viscosity oil such as 10w30! What’s the difference? It is the same type of engine.
The reason straight 30-weight is specified is because air-cooled engines don’t need viscosity improvers since they typically aren’t operated in sub-zero temps. Multi-viscosity motor oils use viscosity improvers (VI’s) in order to get oil to behave like a 10-weight oil at freezing temps, and then to thicken and become a 30-weight oil at 212 degrees F. Since the VI’s take up space in the container, that leaves less room for the oil—which is the actual lubricant. Remember, VI’s don’t lubricate—they only thicken. In other words, a can of straight 30-weight oil has more lubricant than a can of 10w-30 oil. However, a snowblower would benefit from a 10w-30 due to the lower temperatures the engine must run in.
The reason straight 30-weight is specified is because air-cooled engines don’t need viscosity improvers since they typically aren’t operated in sub-zero temps. Multi-viscosity motor oils use viscosity improvers (VI’s) in order to get oil to behave like a 10-weight oil at freezing temps, and then to thicken and become a 30-weight oil at 212 degrees F. Since the VI’s take up space in the container, that leaves less room for the oil—which is the actual lubricant. Remember, VI’s don’t lubricate—they only thicken. In other words, a can of straight 30-weight oil has more lubricant than a can of 10w-30 oil. However, a snowblower would benefit from a 10w-30 due to the lower temperatures the engine must run in.
