For me it lasts around 12 hours. I also have oily skin and this is the best foundation I've tried. It works better than any high end foundation. You get a matte finish but it doesn't look dry or powdery at all.
i work at an arbys restaurant and when i do my makeup i wear all drug store products, and my makeup looks good by the end of 8 hours. it doesnt look like it did when i first put it on but its not god awful and not caked.
So I start work at around 5 am and this foundation will literally stay on my face until I get home at around 8 pm. I have really oily skin and my skin stays matte the entire day! I've even worked out with this on (which I don't recommend just because working out with any kind of make up on is bad for your skin) and it stays looking matte