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Old 05-05-2013, 06:14 AM   #1
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Why warm your engine before an oil change???

I have never understood the idea of bringing your car to operating temp before draining the oil???

I understand that warm oil will flow easer than cold and the theory is that you will get more of the old oil out of the car.

Everyone knows that a large part of engine wear comes from start up. The reason for this......all of the oil has drained from the engine to the oil pan. You will never have more of the engine oil in the pan than when the car has sat overnight. Why would you want to start the car only to recirculate the old contaminated oil through the engine???

I have a different approach to oil changes (in all my cars). the night before I'm going to change the oil, I park the car in the location that I plan to perform the oil change. The next day, I jack up the car where it sits and drain the oil (never starting it). Let it drain for 30-40min and comeback to fill her up with fresh oil. When I do my oil changes in this manor, it always requires the full amount of oil stated in the manual (oil capacity). I figure that this is a good indication that most of the contaminated oil has been drained from the vehicle.

Does anyone else have a theory about this??? I can't see a reason to bring your car up to temp before an oil change???
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Old 05-05-2013, 07:02 AM   #2
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The belief is that contaminants and sludge will settle out overnight (and therefore stay in the engine) if you drain it cold.

Your new favorite oil manufacturer recommends changing oil when it's at operating temperature: Castrol oil change
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Old 05-05-2013, 07:09 AM   #3
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Ditto. Also the design of the flat six engine makes for slow draining of the last remaining oil and even warm should drain for at least 30 minutes. if it were cold it would tale longer still with poorer results.
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Old 05-05-2013, 07:23 AM   #4
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Ditto. Also the design of the flat six engine makes for slow draining of the last remaining oil and even warm should drain for at least 30 minutes. if it were cold it would tale longer still with poorer results.

I understand the slow draining of the flat six. But with my method, the car has been draining for 12-15 hrs. (It has all gathered in the oil sump over night). As far as the sludge, your car is at operating temp when you park it, so I'm assuming the sludge will settle in the oil sump at this time.

I could be completely wrong, but I think the oil companies suggest bringing the car to operating temp because many people don't have the option to change the oil were the car sits overnight (without starting). Therefore, if you start the car (pumping the old oil through the system) it is crucial to bring it to operating temps to not leave the sludge behind and allowing the oil to flow.

I'm not an expert, just my theory lol.
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Old 05-05-2013, 07:47 AM   #5
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I'm with Meat Head. That's how I do it with all my vehicles. The theory is common sense to me. I always end up pouring in the exact amount of new oil that is recommended. Just my 2$ worth.
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Old 05-05-2013, 08:28 AM   #6
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....When I do my oil changes in this manor, ........
If I lived in a manor, I'd let the groundskeeper change the oil when he did the tractor, mower etc.
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Old 05-05-2013, 09:45 AM   #7
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I get the car to driving temperature, shut it off, and let it drain overnight. I also like to pour a 1/4 quart of oil thru the engine as a a little extra clean out.
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Old 05-05-2013, 11:06 AM   #8
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I want to live in a manor too! Do you really think there's sludge in OUR engines? I've always warmed and then drained overnight as well but now i'm wondering...
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Old 05-06-2013, 02:16 AM   #9
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If I lived in a manor, I'd let the groundskeeper change the oil when he did the tractor, mower etc.

I do let the mechanic of my manor change the oil in the box but the groundskeeper just takes care of the landscaping. Doesn't everybody ???? But I give him guidelines on how I want it done

Don't you know, all people that own Porsches live in a manor, ask anyone
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Old 05-06-2013, 05:10 AM   #10
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I'm with Meat Head. That's how I do it with all my vehicles. The theory is common sense to me. I always end up pouring in the exact amount of new oil that is recommended. Just my 2$ worth.
+1. Cold oil drains, just slower.
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Old 05-06-2013, 05:27 AM   #11
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Gotta love car guys. Having grown wary of endlessly debating which oil is best for our cars, we will now endlessly debate the best way of draining said oil from our engines. I can hardly wait for the discussion on how best to pour the new stuff in. (I like to pre-heat mine in the microwave first so as not to shock the delicate internal parts with cold oil)
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Old 05-06-2013, 05:32 AM   #12
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Originally Posted by Meat Head View Post
I understand the slow draining of the flat six. But with my method, the car has been draining for 12-15 hrs. (It has all gathered in the oil sump over night). As far as the sludge, your car is at operating temp when you park it, so I'm assuming the sludge will settle in the oil sump at this time.

I could be completely wrong, but I think the oil companies suggest bringing the car to operating temp because many people don't have the option to change the oil were the car sits overnight (without starting). Therefore, if you start the car (pumping the old oil through the system) it is crucial to bring it to operating temps to not leave the sludge behind and allowing the oil to flow.

I'm not an expert, just my theory lol.
Hmm. In my experience the rate of flow becomes absolutely teeny after about an hour. Can't really see the benefit of leaving it overnight. However you do it, there's going to be a fair bit of old oil left. Well, unless you fill it, run it and flush it a few times before refilling.

If you want to really reduce the amount of old oil residue, I think you need to completely fill it after draining, run it for a while and then dump and refill. Leaving it for hours and hours to drain doesn't make much difference to the residue stuck to all parts of the engine.

Personally, I just drain it for about an hour from warm and refill but I do my changes fairly frequently - around every 5k miles - so I really don't worry about a little residue. Fortunately, these cars take a **************** load of oil, so any residue gets pretty well diluted.
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Old 05-06-2013, 05:37 AM   #13
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Gotta love car guys. Having grown wary of endlessly debating which oil is best for our cars, we will now endlessly debate the best way of draining said oil from our engines. I can hardly wait for the discussion on how best to pour the new stuff in. (I like to pre-heat mine in the microwave first so as not to shock the delicate internal parts with cold oil)
Since my kids are grown, I use their old bottle warmers
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Old 05-06-2013, 05:38 AM   #14
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Gotta love car guys. Having grown wary of endlessly debating which oil is best for our cars, we will now endlessly debate the best way of draining said oil from our engines. I can hardly wait for the discussion on how best to pour the new stuff in. (I like to pre-heat mine in the microwave first so as not to shock the delicate internal parts with cold oil)

I'm pretty sure that is what these forums are all about. I don't consider most of these discussions a debate??? In my opinion, forums are just great places to bounce ideas off of hundreds of people. Many times someone points out something that I hadn't even thought of. I like to throw my 2 cents into the mix and see everyone else's theories from different perspectives.

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Old 05-06-2013, 05:46 AM   #15
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Hmm. In my experience the rate of flow becomes absolutely teeny after about an hour. Can't really see the benefit of leaving it overnight. However you do it, there's going to be a fair bit of old oil left. Well, unless you fill it, run it and flush it a few times before refilling.

If you want to really reduce the amount of old oil residue, I think you need to completely fill it after draining, run it for a while and then dump and refill. Leaving it for hours and hours to drain doesn't make much difference to the residue stuck to all parts of the engine.

Personally, I just drain it for about an hour from warm and refill but I do my changes fairly frequently - around every 5k miles - so I really don't worry about a little residue. Fortunately, these cars take a **************** load of oil, so any residue gets pretty well diluted.

If you read the entire thread you will see that I'm not saying drain for hours . I'm saying if you let the car sit overnight (do not start before draining), it is equivalent to draining for hours because the oil has gathered at the sump. At this point 30min should drain every possible bit of oil out of the engine. If sludge is your concern, because the car was parked at operating temps, I would assume the sludge would also gather at the sump at this point.
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Old 05-06-2013, 07:16 AM   #16
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I'm in the drain the oil while it is hot camp. For two reasons particularly:

1) Particles have a tendency to be picked up better by hot oil and flushed with the oil change.

2) Sludge does not even move when cold. The "sludge" generally contains the most particles.

Depending on vehicle age, oil type, oil change frequency, etc. you might be surprised by what is left on the bottom of your oil pan just waiting to be mixed in with your fresh oil as it heats up the next time.
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Old 05-06-2013, 08:35 AM   #17
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I'm pretty sure that is what these forums are all about. I don't consider most of these discussions a debate??? In my opinion, forums are just great places to bounce ideas off of hundreds of people. Many times someone points out something that I hadn't even thought of. I like to throw my 2 cents into the mix and see everyone else's theories from different perspectives.

I wasn't being serious or critical - just joking around and poking at bit of fun at us car guys about how anal we can get about our hobby.
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Old 05-06-2013, 08:49 AM   #18
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I'm in the drain the oil while it is hot camp. For two reasons particularly:

1) Particles have a tendency to be picked up better by hot oil and flushed with the oil change.

2) Sludge does not even move when cold. The "sludge" generally contains the most particles.

Depending on vehicle age, oil type, oil change frequency, etc. you might be surprised by what is left on the bottom of your oil pan just waiting to be mixed in with your fresh oil as it heats up the next time.
Yeah, I think you've sold me. I'll stick with doing it with the oil hot.
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Old 05-06-2013, 08:52 AM   #19
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If you read the entire thread you will see that I'm not saying drain for hours . I'm saying if you let the car sit overnight (do not start before draining), it is equivalent to draining for hours because the oil has gathered at the sump. At this point 30min should drain every possible bit of oil out of the engine. If sludge is your concern, because the car was parked at operating temps, I would assume the sludge would also gather at the sump at this point.
As you say, what you are doing is equivalent to leaving it to drain for hours. And as I've said, not convinced of the benefit of that.

Mr Knowles has made the clinching argument, I feel. That sludge that has collected over night may not be terribly mobile when you attempt to drain cold the next day.

Drain it hot and nicely mixed up and you can be confident you'll be getting the vast majority of the unwanted gunk out.
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Old 05-06-2013, 11:16 AM   #20
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FACT: After draining oil for one hour, remove quantity and place cup under car. Wait overnight or 12 hours. You will find about 500ml (pint?, half quart, almost full coffee cup). I've been doing it that way for 13 years. Facts is facts!-as opposed to mental foreplay...
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