bijiminy
Active Member
- Joined
- Aug 17, 2020
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I've been thinking about this: If 15w40 oil were recommended, wouldn't straight 30w be okay? It seems in colder ambient temps the thickness of the oil would be on the 40w end and at hotter ambient temps the oil would be at the 15w end. I know it should be just the opposite, because of the additives, but I used to run 15w40 year round in my diesel Ford. It was extremely hard to start in cold weather unless I had the block heater plugged in. When I changed to year round 10w30 diesel oil on Ford recommendation, it was much easier to start. 15w40 would sort of be on a sliding scale so to speak. It has to go through the oil hole feeding the bearing, and this oil would be 30w at some point. Feeding the bearing is the whole issue. Most people only use their lawn equipment from early spring, when it relatively cool but not cold to late summer when it very hot. So, to me, straight 30w makes sense or is my reasoning way off?the oil has to float the bearing
What decides if it can do this is, the size of the oil hole feeding the bearing, the pressure that the oil is under , the space between the journal & the bush , the viscosity of the oil.
The first 3 are manufacturing fundamental of the particular engine