Oil weight

[Grumpy Bear]

 

Taken a bit less literal was the idea that even the same displacement and motor type used for different purposes MAY have different viscosity requirements based on slightly differences in motor build specifications. Temperature is a factor in wall film thickness. Water contributes. So does load. So does viscous drag. 

 

10W30 use to bread and butter when wider high tension rings were the mainstay of Detroit. These new motors with the ultra thin low tension rings would have some issues scrapping enough oil from the walls on the exhaust stroke. 0W20 is a part of the cure. In part, the reason for low speed spark knock and modifications to oil chemistries is tied to that concern. Then again 0W20 in a Gen 1 SBC? Those rings of that period would wipe the wall dry. Water jacket of the day ran 25-30 F cooler. That would actually be a plus and that fact used, as stated earlier, when temperatures fell and 20W was used over the winter. 

 

As far as radiator sizes. No comparison to 'back in the day' copper core, brass tank to plastic tanks and aluminum cores of today. They're larger because they transfer poorly. Yesteryears motors were less thermal efficient as well. Drove truckloads more heat into the water even at lower hp/liter levels. 

 

Look, all I'm saying is we can't say 'blanket statemet' style that it is bad for GM to spec a lighter oil. I'm not going to buy into the 5 year 100K life limit of a motor that has to compete with Asian motors that will go three times that long. We have to many examples in this community to debunk that notion.  Even GM's own belated 3.8 V6 is good for 300K plus pretty reliably. There's a dozen or so in my own family over that mark. Buick/Olds…...

 

Anyway...enjoy the evening and be safe.