Car is a civic vti 1999.
I've asked on forums and honda themselves who said so long as my weather isn't extreme one way or another, I should use 0w30 or 5w30 engine oil.
When I went to pickup the oil from my local parts store they told me I need to be using 10w40 because my car is old and showed me some specific oils. When I said honda said he replied '..well they would because they want to sabotage your car. older cars do not do well on the new stuff they will put strain on your engine..'. I can't remember if the oils he showed were synthetic or not.
Is there any truth in this?