First thread on this forum for me. This tip is courtesy my first oil change in my 97 Acura 2.5TL.

I've been changing oil in cars for 40 yrs or more and thought there was nothing to learn about this fundamental task of auto maintenance. I think I discovered something that may be useful on many models with oil filters that are horizontally mounted.

I ran the Acura up on ramps and drained the hot oil (engine fully warm). I decided to let the engine cool a bit and let the draining continue to dribble into the catch pan. After taking a break, I came out to remove the oil filter. On the 2.5L engine the oil filter is mounted horizontally under the throttle body on the driver's side (engine is inline). It's easily visible and touched, but a bit tricky to access for loosening and removal. I was able to break it loose w/ my left hand, and loosen w/ my right hand. It was still very warm and I didn't want to spill hot oil on my arm in removing the filter through the narrow access passage. So I left the loosened filter in place to cool some more. When I stepped back I noticed that a steady stream of oil was draining from the crankcase drain. I was surprised since this had to be oil from the oil filter. So I watched while the stream ran for a minute or so and returned to a dribble.

Here's what happened. When I loosened the oil filter, I allowed air to vent into the filter and oil to flow downhill from what was formerly a atmospheric pressure lock (usually called vacuum lock). Basically, the air pressure is holding the liquid in place because the drain opening is too small to allow air to run around the liquid and gurgle (viscous effect dominate pressure effect in a narrow passage).

When I finally removed the oil filter, there was no oil loss, and total loss from the filter appeared to be perhaps a tablespoon during the initial loosening. Even this might have been avoided if I had loosened the filter less.

This experience suggests you can avoid the inevitable messy loss of 2-4 oz of oil from the oil filter w/ similar practice on Accords, or likely any car w/ horizontal filter mount that will allow the filter to drain, at least partially. Oil will drain from the filter till level is below the mounting tube level.

Here's a pic of the Fram Anti-Drainback Valve arrangment. It's the 3rd Picture. Air can enter once you've cracked the filter, but oil can't come out, except through the engaged threads. This allows most oil to drain into the crankcase via the oil return, threaded filter mounting tube.

Fram Oil Filter Anti-Drainback Flap Valve

I would appreciate feedback from folks who try this.

regards