Burnsy

foil and a rubberband, good thought, i was trying to think of what to put over it, and kept coming up with tape, which isnt ideal

Nuke

Get one at the dealer or hit a junkyard. I doubt the oil is contaminated but it's cheap insurance and piece-of-mindto change the oil and filter.

GidyupGo

It should be fine. If allowed to remain open for a while, it could be an avenue for moisture to get into the oil from the air. Turn it into that yellow peanut butter looking stuff. Unless a chunk of gravel road got up into there, it should have received nothing worse than a little dust.......nothing the filter can't take care of.

ModernMuscle

we swapped oil at the track one day, and a lot of things went wrong with a friends car right as I put the last quart in...needless to say, we ran over to help, and forgot about the cap.
I made a pass, and got an oil light at the end.
But cehcked it, and put the cap right back on, and it ran perfectly...

GidyupGo

Did he slosh oil out or did a sensor just pick up that it was no longer a closed system?

28HopUp

When you get a replacement cap, be sure to tell the clerk that you need a "710" cap.

AdderMk2

I was just going to recommend that. People have no idea how important the 710 cap really is.

marcuskeeler

I would be wary of putting foil over it. A motorin good condition and with the PCV system working as it should, the valve areas should be running at a lower than atmoshperic pressure, or in other words, it will be sucking. Foil isn't that tough and might break up allowing bits of metal foil into the motor.
A lightly oiled rag is best, with a clamp round it to keep it taut.

Nuke

OK, I'll bite... WTF is a "710" cap?

rford426

yea what is a 710 cap???