I sell boats for a living and most contain Volvo sterndrives. The engines are actually GM marinized by Volvo. Synthetic lower unit lube and synthetic engine oil are REQUIRED for warranty purposes. The catch is that they require their own brand (what a surprise) of lubes be used. Right on the oil fill cap it says 30weight synthetic only. We have it in 55 gallon drums and it clearly states synthetic 30. I am curious as to the maker of this oil and if there is actually such a thing as a straight 30 in a synthetic. It seems all are multi-vis except this one.