If you mean this chart extracted from the Kawasaki FR730V manual, [Linked Image]

then I see what you mean. But unless oil consumption at higher temps becomes noticeable, there probably isn't anything to be gained by using SAE40, in terms of engine life.

SAE40 monograde oils are available, but are usually intended for diesel truck engines, specifically the GM/Detroit 53, 71 & 92 series 2-strokes [it's OEM Spec for these]. So it's sold in 20L and up sizes, and may not be the best formula for small petrol engine use [e.g. the Penrite Mono Truck 40 has lower antiwear additive by ~25% than the SAE30].

Cheers,
Gadge

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