Lots of cars in Australia, of all types, running around on 15W40. Simply because all the majors make a 15W40 and sell them at a very low price point. You can get Castrol GTX, Shell Helix HX5, Valvoline Engine Armour and many others, all as 15W40 PCMOs. You can run them year round in our climate.
Mostly they were mineral oils rated API SN/CF and ACEA A3/B3, with natural low Noack and good shear stability. HTHS was around 4.0 - 4.1 cP, from the few that published this data.
More recently some have become semi-synthetic, e.g GTX UltraClean 15W40, and some like the Valvoline EngineArmour / DuraBlend have been upgraded to API SP, Euro ACEA A3/B4 and VW 502/505.
I was at a fuel station recently, and a guy in a nice suit and driving a new Audi bought some mineral 15W40, and I watched him pour it into his engine. He must have got a low oil light or something. Probably not the correct oil, but it will work just fine. At least he topped it up. A friend of mine has a Subaru WRX with the boost turned up, his mechanic told him to run a 15W40 HDEO, and that's all he uses.
I know it seems strange to the North American market, but over here, many people use 15W40 without concern. I often use it myself, and my oil stash contains GTX UltraClean 15W40 and Mobil Delvac 15W40 mixed fleet HDEO.