Gas cap
 

So here's the scoop.
The gas cap was put on crooked the other day and became jammed.
This has happened before and is a quick fix for me.

Well this happened while I was at work and I told my wife that I'd get it when I got home.
Well her cousin's boyfriend decides he is gonna wrench on the friggin cap untill he finally manages to snap it off, duma$$.

Anyways, enough with my bitc# rant...

I put a different gas cap that I had laying around on the 3, it fits but now I'm recieving a CEL.

Would this cap be the source of this CEL, due to it being a screw on cap instead of the Quarter turn-then lock cap it had?

Since the advent of the OBD-II era (mid to late 1990s), if you put a gas cap on your car (any car, any make, any model) that doesn't seal exactly like the factory cap, you'll get a CEL. Put the proper cap back on there and the CEL should extinguish itself after half to three quarters of a tank of fuel.

Yea, I'll get around to buying one eventually.
Unless I can convince the service guy it was a manufactering malfunction and it was their fault it broke....then warranty will cover it....LOL

That shouldn't be a difficult sell at all. Why? Given the huge numbers of problems with the 2008 model year gas caps, if the service guy says he doesn't know about the problem, then he's lying. ;)

I'm the same as you... sometimes my cap gets jammed too. A little jiggle work and it comes off.

A loose, wrong, or improperly fitted gas cap doesn't seat properly, causing an EVAP loop failure which puts the CEL on.
Mazda screwed up on the original design which easily goes on cross-threaded; some need to be crushed to death with a pair of slip-joint pliers to extract them.
You can get the redesigned replacement under warranty, but don't ask them about it, tell them about it (and bring the slip-joint pliers with you for persuasion: if the service manager knows the difference between a rooster and a capon he'll get the message).

I'm on the road as early, if not, earlier than you, so yeah... I know what you mean. I generally don't get gas in the mornings though. I live just a few miles down the freeway from the warehouse so it's not often I need to gas up in the morning.

But still... yeah. I will have times that I'll go to take it off and it doesn't move at all...