My new lawn tractor calls for SAE 10W-30 but some Internet sites recommended the use of SAE 10W-40? Which one should I use? Also is using a synthetic recommended? Thanks.”
Halderman:
I always recommend what the vehicle manufacturer specifies to be used. The engineers know what is best for the engine; in your case, using SAE 0W-20 is the right viscosity to use. Here is the good news. If there is a “0” at the beginning of any oil viscosity rating, it has to be synthetic to be able to meet the specifications.
Regarding your lawn tractor oil: I would again recommend the use of the specified SAE 10W-30. Using the SAE 10W-40 means that it has more viscosity index improvers added to make it suitable for the wider viscosity range. The extra improver additive has been known to cause piston rings to stick, leading to increased oil usage.
Staying with a known, brand-name SAE 10W-30 and using a synthetic one is a wise option, in my opinion. Change the oil in the lawn tractor as specified by the manufacturer, which is usually every 25 hours of operation.
Have an automotive question? Write to Jim at jim@jameshalderman.com.
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