kkim

For those that change their own oil... How long to you let the oil drain before buttoning things back up? I've read where leaving the system to drain for an hour or more can significantly increase the amount of oil that drains. I've not been doing this and have only waited like 30 minutes or so.

So, is there a significant amount of oil to be had by waiting? If so, I'll be sure to do this on my next oil change.

Thanks for any feedback

Flying Finn

I doubt that.

When I change oil, after about 10-20 minutes there are only drips dropping, say in every 2 seconds. So if you wait for an extra hour, (assuming the dripping will continue same rate, not slowing as I'm sure it will) you'd get about 1800 drops which is like (wild guess), a cup? How it could be significant amount I don't understand.

Since there is always about quart oil left in 993's oil cooler & lines anyway, I wouldn't bother waiting for an hour or more.

BTW, you do warm up the engine before you drain the oil.

TheOtherEric

Interesting question. Let me take a guess. I'd bet that waiting an hour would get you about 1/4 cup of oil drippings. For a 12-quart system, that's an additional 0.5%. Don't know about you, but an hour of my time is worth more than 1/4 cup oil.

I nominate YOU to take a measurement. Let's have a pool to see who guesses the closest.

kkim

I warm it up, but I don't get the engine to full operating temp.

Also, I guess it's just as important to have both front and rear of the car jacked up so oil can flow back in the lines? The last time I did an oil change, I only lifted the back and am questioning if that is a bad practice.

TheOtherEric

Finn,
1800 drops is 1/2 cup. In other words, 1% of the system's 12-quart capacity.
http://www.firstrays.com/convert.htm

the_buch

I was wondering if anyone uses one of those siphon-based oil evacuation systems by placing a long tube down the dipstick opening and drawing the oil out of the engine. This used to work wonders on my M3 and then I didn't have to worry about the drain plug at all. Of course, life was simple because the oil filter canister is on the top of the engine and replacement was a three minute job :-)

If the dipstick allows access to the full sump, these systems can get as much oil out as draining. The capacity of my pump is only six litres so it would take a couple of siphon sessions to do this job??

Regards,

Ray Calvo

When it stops dripping, then I button things up. 10 minutes or so.

Arrwin

I sure hope it's not bad practice.

CentralCoastC4S

I did my '97 oil change last weekend. I warmed it up and jacked up the back of the car, got the jacks positioned where I wanted them, pulled the drain plugs and let the oil drain for about 5 minutes. Just to see how much I was missing with just the rear end up in the air, I put a second jack under the front jack point and lifted the car from the front. I got maybe 1/4 of a quart out, that's about it. It didn't make a huge difference but then again, it's pretty easy to do. Once the drips stopped or slowed way down (about 30 mins) I dropped the front back down and started buttoning it back up.
BTW, I removed the oil return tube to increase access to the small filter, be careful when doing so as the tube tends to have a lot of resistance and then all of the sudden it's out and a lot of oil comes with it. Took an oil shower. Had to stop the process and take a real shower. Kinda messy. But it really helps access to the small filter.
I think it's safe to say that the rate of flow of oil is directly proportional to the heat of the oil. I hate burning my hands on that stuff so I just get the engine up to temp and no more. You'll get all the oil you need out and the heat exchangers won't fry you.

paradisenb

I'm curious how hot the engine needs to be? If it gets hot enough to open the front oil cooler it will burn the **** out of your hands if there is even a small hole in your gloves. Ask me how I know.
I did this with the 911.
The 993 need to have an oil change and I would like to do it myself, but not if I'm going to repeat my last experience. Is luke warm OK? Even if the cooler does not drain?

CentralCoastC4S

Randy, I'm sure my cooler did not drain. Is there any evidence you can ever really drain the cooler, no matter what the temps, if you don't unhook the lines at the cooler and physically drain it? Seems to me that during any oil change there will be residual oil. It's just a matter of how much oil gets left.
Get the engine warm. How warm? I just get the temps up to 180 or so and get it on jack stands and go. With as often as most of us change the oil, I can't see a problem.

hatchy

Does anyone know the answer to Doug's question (I'd like to know as well). I use the same method on my wife's C32 and oil changes take about 10 minutes.

Edward

I wouldn't use the siphon hose-in-the-dipstick pump. There is still a considerable amount of oil in the crankcase ...can't remember offhand, but I know that the drainpan I put under there gets quite a bit of oil, maybe a quart+ ???
Moreover, if you're changing filters anyway (and you should), you're really not saving much time.

Edward

Flying Finn

Kelly, Randy

I don't warm the engine to proper driving temperature, just to get the gauge to raise some is enough for me (for those burning reasons...).

I've been wondering whether it would work if you'd warm the engine hot ehough to get the thermostat open and that way be able to drain all the oil out.
I don't know exactly how 993 thermostat works but I figured it wouldn't work like that since every time I shut the engine when thermopstat it open and then if I start it almost immediately and start driving again, thermostat is closed... I guess it sense when flow stops or is electrically charger or? In any case I don't think it works.

I always change oil boith ends of the car up (so that the car is level), I don't actually jack the front up but drive front wheels on my home made ramps, and then just jack the rear and put on jackstands.

Eric,

Well even less then so no way it's worth spending extra hour waiting, espoecially since that 1/2 cup is way less because dripping will slow down...

Doug, hatchy,

Don't get me started on that damn siphon thing (check earlier posts on this)...

It is not advisable to use these sucking systems in our cars (personally I woudn't do it in any car). in 911s that have dry sump (as you know, some of them new water pumper 911s don't have it) which meand sucking from oil tank will get only little over half (maybe 3/4) of the oil out, rest of it you need to drain from the crankcase so no, it just doesn't work.
Not to mention advances on draining when it comes to getting all the "crap" out.

Aaaand finally, why think about sucking the oil since draining it really is the easy & fun part of 993s oil change, PITA of 993 oil change is that damn smaller oil filter!