OK so a few months ago I was driving on the interstate and when I came to a stop I noticed a gas/oil smell. I thought nothing of it and thought it was coming from the semi in front of me but when I got to work and got out of the car I noticed it against so I popped the hood. Low and behold there was oil all over the engine compartment and a closer look revealed that my oil cap was missing. I figured the oil cap was loose and finally popped off but then I thought I haven't had an oil change for a couple months so why did it take so long for it to come off if it indeed was loose. So I thought maybe pressure built up and it popped off but when I looked at the cap which was sitting on the right side of the engine there was no damage so I assumed it did come loose. But here's the thing, ever since that happened I have an oil leak that only happens when I start the car. A considerable amount of oil leak from somewhere I have yet to find to the point I have to keep an eye on it and replace about a quart of oil a week. I'm thinking maybe pressure did build up which caused the oil cap to pop and also maybe created a hole in a seal somewhere under the engine. My question is does anyone have any ideas what and where this leak could be coming from? Like I said it only leaks when I first start the car after its been sitting for awhile. Also any ideas what would have caused my oil cap to pop off? I'm positive it wasn't loose and didn't just rattle off. Any input or ideas would be appreciated. I'm tired of replacing quart after quart of oil. I had a mechanic look at it and said he couldn't find an oil leak but he said there was quite a bit of oil under there.