breather hose/MPG question

[Cyrus2000]

im curious as to whether or not your PCV breather hose is clamped onto the valve cover vent nipple or just loosely placed over it. mine was so loose it showed no resistance at all if you tried to remove it, literally you can lift the hose off with your pinky. i put a hose clamp on it today.

possibly unrelated, i just recently fixed my fuel filler neck (big puddles of gas under the trick if i let it fill til the pump auto shuts off). So on my last tank of gas, I noticed a HUGE drop in MPG. I was averaging 24mpg before, but averaged 16mpg on the last tank (20 gallon tank). I also used to have lots of pinging on the highway under load, like going uphill in 4th or 5th gear, but not anymore. I didnt think to check it with breather hose unclamped, but now with the filler neck and the breather hose clamped, it doesnt ping at all. I've been putting 89 octane in which helped a bit with the pinging, so I'll have to try 87 and see what it sounds like now. so i just want to know if that breather hose could let in enough unmetered air to cause a lean condition that gave me better gas mileage. and could the filler neck having a huge hole in it have contributed in some way?

 

[srteach]

The breather for the PCV will let un-metered air into the intake, depending on how loose it is and if the vacuum applied to the tube seals it. The O2 sensor will read a lean condition in the exhaust, and send a signal to increase fuel input if it is operating correctly. This will cause premature detonation (sometimes interpreted as ping). Fuel mileage will usually decrease in this condition, though some other engine controls may compensate or counter the condition.
That being said, I doubt the slightly loose PCV hose is causing the mileage issue,but it is a good idea to seal it properly.