What weight oil

[Grandpa]

Using technology, when not necessary, is plain silly and a total waste of time and money. Whatever advantage, if any, can be derived from adding this junk to a motorcycle engine is subject to the law of diminishing returns. It not only does these additives not help your wet-clutch engine and oil-bath transmission; it may even be harmful to your engine/clutch/transmission.

I strongly recommend to anyone reading this to stay away from anything in your engine other than a good-quality oil changed regularly with the oil filter.

Use of additives of any kind is not recommended by Suzuki. I would think that a motorcycle like my GK, which has been on the road for 118,000 miles, with not a bit of engine, or clutch, or transmission trouble, and no teardowns past the valve cover, is proof enough that this junk is unnecessary and a total waste of time and money.

I'm out of this thread. Waste your money on this junk if you want, y'all. :-D

[KEITH KRAUSE]

Use what the factory recommends. On a '78 GS1000?, I'd run 10/40 all year, unless you have a lot of hot summers and city riding to do. 20/50 may be used under hot conditions but be sure you have stock clutch fibers. Many aftermarket plates will allow clutch drag if you run 20/50.
I run 10/40 Motul 3000 all year on my '79 GS1000.