New X5 owner needs advice on end-of-warranty and gas cap warning

[wwu123]

Hi, new to the forums and proud new 2007 pre-owned X5 owner as of about six weeks ago. Have put about 1500 miles on the car, and it pulled through like a trooper during the holidays shuttling extended family around town and to Lake Tahoe, particularly with the third-row seat for the pre-teen relatives.

Need some advice from the experts here, I'm at 49,100 miles, so just a few weeks shy from the end of the factory warranty. The "check gas cap" warning has already triggered the check engine light once, forcing a trip to the dealer to reset it. I attributed that to user error after my first fill-up.

However, since then the red gas cap warning diagram has flickered on and off a couple of more times, forcing me to pull over and tighten it, and then once again once before I was able to pull over, the check engine light came on within 15 seconds and stayed on.

I have an OBD scanner that confirms the PID code most associated with a loose gas cap. But this was 300 miles into that tank of gas, so I don't think it was user error. I'm definitely planning to bring it in to the dealer before the original warranty is up, but aside from them just resetting the light, what else should I insist they check?

1. Should I insist they check for a leaky or failed part? Is it likely there's a vacuum or seal leak somwhere, and the light will keep coming on?
2. Or is it possibly a temporary condition due to water in gas/low-grade gas/ temp fluctuations (there have been some cold spells and rain)?
3. Will the check engine light eventually go out by itself? It hasn't so far after 400 more miles. My service advisor claims it will, but I read that on some models it will never go out by itself.

I do have the CPO warranty that kicks in, but aside from not wanting to pay $50 deductible every time this happens just to reset the light, it's a hassle and minimum 1-1.5 hours to the service dept each visit, and I've already been in three times for misc small warranty items. And if there is a failed part, I'm not sure "emissions" stuff is covered under the CPO warranty?

Thanks in advance for your input,

Warren