Hehe, gender was not specified, so no problem! I roger you.
Just digressing a bit as I have been wondering, how about rotary engines? I was told that they need to use fully synthetic but what I've always seen is they use GReddy or some oil imported from Japan. Rotary can use 5w-40?
OMG.. I think I'm in love
A girl who knows her oils and knows what a rotary is!
If you're driving a perodua, using the 5W40 isn't going to destroy anything. The only thing is it'll feel really heavy when you're driving around since the recommended weight is 5W30. Personally, if you have a friend who has a Toyota Vios, Proton Wira, Gen2 or Persona, you can give/sell that 5W40 oil to them. I wouldn't use it on my Perodua. BMWs are very sensitive machines, I wouldn't use anything other than the recommended oil weight the service manual dictates.
As for rotarys, there's a lot of debate going on regarding it. Because the engine is so sensitive to heat, the oil that helps dissapate heat the fastest and prevents build up is the best imho. Most of the rotary kakis I know use mineral 10W30 or 10W40 at most. 5W40 and 5W30 on a rotary shouldn't be a problem but since most of them change oils at 3000km, semi-synthetic or fully synthetic oils are quite pointless.