No mention of weights on that chart at all.
Here's the way I understand it, and if I'm wrong, I'd like someone to
explain it to all of us.
Oil gets thinner as it gets hotter. Through more high-tech refining, it can
be stabilized over a wide temp, displaying multiple weights.
- 10w oil is thin; sewing machine and 3-in-1 household oil are 5 or 10w.
- 30w is about right for a warmed-up gasoline engine.
- 90w is the gear oil used in the rear end, thick and syrupy.
- Multi weight oils cover a wider range; 10-40, when it's cold, won't get
thicker than straight 10w, and when it's hot, won't get thinner than
straight 40w. This allows it to cover a wide range of driving conditions.
- 10-30 is fine for most driving, but not as wide ranging as 10-40.
- If you ride an air-cooled bike, you'll have a very wide range of
temperatures, and probably use 5-30 in the winter and 10-50 summer.
- In the winter, when your engine never gets very hot, 10-40 is probably
overkill. 10-30 would be fine.
- If you live where it's hot and never gets cold, you'd probably be OK with
straight 30 or even 40w. You need the multi-weight to keep from bogging
down a cold engine.
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