Thanks for your imput but tell me why in Australia they mainly use W40 weight to deal with their heat ?? 5W40 10W40 15W40
I have not heard of Australians doing that? but until just now I've never looked either haha. but quick Google showed Toyota and Mazda both recommended 5w30 for new cars? Fords and chevy didn't show up in my quick search.
can you point me to some info? be interesting.
I don't have it handy, but I've seen a chart about oil viscosity based on oil temperatures, something like a 50w racing oil is about like a 5w30 at 320deg oil Temps. that plus how much load your engine is seeing at those Temps corresponds to the oil wedge needed to keep the bearing from touching the crank. but it was a deep dive into racing engines and kinda general.
in the newer c7 z06 corvettes. the ones with the supercharger and meant for track days, they still need dexos for daily, so there's a new "supercar" branded mobile 1. I believe it's a 0w40 so you get thicker than a 5w30 but won't kill the cats, which is the dexos rating is for. but for track days the owners manual says to change to a straight sae 50 mobile 1 racing oil and then change back as soon as the track day is over. the cars are notorious for very high oil Temps in track settings,(as well as over 600hp) and that's the work around. even thou the 50 racing oil is full of zinc, which is great for lube but causes ash that is said to be bad for cats. I personally have run all kinds of stuff with the oem cat still fine on my obs. so I'm not sure how much that matters but gm says oil needs the dexos meaning low zinc rating for long cat life.
also there's one chart that recommends oil weight based on bearing clearances you built the engine too, iron block and aluminum block. aluminum growing more for the same Temps, so clearance ends up different for different Temps kinda thing.
I was listening to that milling oil pump webcast and someone did ask a question about if they could gain hp by running thinner oil in older cars like that new 0w16 stuff in a 60s car by adjusting bearing clearance to tighter spec. the guy on there said it's probably not good to try and reinvent the wheel with 60s technology engines. just run what it calls for and build hp a eaiser way.
now this is all racing stuff. nothing I've seen geared towards our stock daily drivers but I I'm curious. like I've wondered if i could run that 0w20 in my truck. since it's got a variable displacement oil pump. but then I talk myself out of it cause what's the point really haha. it already gets good mpg for a big suv. 0.5 more won't really matter.