Is draining oil better than siphoning it out?

Dear Car Talk

Dear Car Talk | Jul 01, 1997

Dear Tom and Ray:

The quick-oil-change dealer in my town has begun
to siphon the oil from cars through the dipstick
tube. He still changes the filter and the new oil
looks clean. But it seems to me that debris could
be left in the oil pan at the bottom of the
engine, causing problems. What do you think? --

RAY: I don't think it's a problem at all, Keith.
I think it's a great idea. It'll probably even
remove some stuff that you wouldn't get out
through the normal oil-change process.

TOM: Whichever method you use, you're only going
to get about 95 percent of the old oil out. But
that's good enough. And the advantage of sucking
the oil out through the dipstick tube is that it
eliminates the possibility that some
knuckle-scraper at the quick-oil-change place is
going to strip your oil pan by overtightening the
drain plug.

RAY: Or not tightening the plug enough, and
letting your oil drip out on the road as you
drive home.

TOM: So as long as they change the filter, we're

RAY: Of course, they could accidentally suck out
your transmission fluid! But we'll give them the
benefit of the doubt of knowing which dipstick is
which -- at least until we hear from our readers

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