Draining oil without removing filler cap?

[OceanRuns]

Just did an oil change. Forgot to unscrew the filler cap while draining. Did remove the filter.
Older car, first change, no idea of the amount it should take. Let it drain for about 10-15 minutes. Still had a drip going when I sealed it back up, but also didn't warm it up a lot.
Does not removing the filler cap 'hold' (vacuum) oil in?
Think 10-15 minutes got enough that no real difference exists?

 

[Whimsey]

Opening the oil filler cap helps drain the oil faster I find.

Whimsey

 

[samven]

No, just takes longer to drain. I always remove the drain plug first and then take the cap off to avoid the huge gush but really its not air tight even with the cap on if you have a dip stick.

 

[Traction]

In my 50 years of changing my own oil, I have never took the oil cap off to drain oil. The crankcase is vented. More important is to remember to do everything else right, and not to forget to put the cap back on. I did that once, so far.

 

[eljefino]

Originally Posted by Traction
In my 50 years of changing my own oil, I have never took the oil cap off to drain oil. The crankcase is vented.



And if it weren't vented the oil would still drain, it would just glug as it brought air back in.

 

[Snagglefoot]

Depends what vehicle you have.Try it both ways and pick the one you like. Mine do not glug. The crankcase vents to the intake.

 

[Chris142]

The crankcase is vented. Removing the cap will have no effect on the drain time.

 

[OilUzer]

Originally Posted by eljefino
Originally Posted by Traction
In my 50 years of changing my own oil, I have never took the oil cap off to drain oil. The crankcase is vented.



And if it weren't vented the oil would still drain, it would just glug as it brought air back in.


it may also lube the calipers for you

 

[Hall]

I'd say that I've done oil changes without removing the cap more than the times I've remembered to remove it. It's by no means necessary so don't give it a second thought. 10-15 minutes draining is more than long enough too. It will 'drip' for hours if you let it so don't use that as an indication of much either.

 

[bbhero]

Exactly right ↑↑↑↑

 

[TheLawnRanger]

I usually forget and say I'll get it next time. I put the same amount of oil back in and if it shows different on the dipstick, it's microscopic.

 

[Triple_Se7en]

I think my Hyundai owners manual states to remove the oil cap and dipstick prior to opening the drain plug. Now I'm employing the same proactice on all three vehicles.

 

[JeffKeryk]

I think you gotta take it off sooner or later.

 

[92saturnsl2]

I've never removed the fill cap when changing oil and it always comes out plenty fast if the oil is warmed up.

Next time I change the oil I'll try removing it and see if I notice a difference-- I doubt there is.

 

[slacktide_bitog]

I'd be afraid of the oil cap not coming off after you already drained the oil

That's why you should take off the cap first

 

[Jimmy_Russells]

Part out

 

[dishdude]

I've never pulled the fill cap to drain oil.

 

[ecotourist]

Originally Posted by slacktide_bitog
I'd be afraid of the oil cap not coming off after you already drained the oil

That's why you should take off the cap first

Agreed. I was told that when doing any fluid replacement, you should remove the fill plug before removing the drain plug. That way you never end up with the fluid drained and no way to replace it. So for an oil change the cap comes off first.

 

[clinebarger]

That's more for transfer cases & differentials because the fill plug is also the check hole/plug. Ford's ratcheting oil caps are the only ones I've ever had issues with.

 

[Black_Thunder]

you could also just loosen it partially just so the seal isn't in contact with the fill and it would probably give just as much of an effect as removing it completely