Why warm your engine before an oil change???

[Meat Head]

Originally Posted by mountainman

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.

[1olddude]

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.

[Joe B]

Originally Posted by 1olddude

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.

[pothole]

Originally Posted by Meat Head

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.

[Meat Head]

Originally Posted by pothole

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.

[pothole]

Originally Posted by Meat Head

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.

[woodsman]

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...

[pothole]

Originally Posted by woodsman

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...

500ml is one hell of a big cup of coffee. Especially one that's only almost full. Would suggest a cup of coffee is typically sub 200ml. Which is it, a cup of coffee or 500ml?!

[woodsman]

400 ML or an almost full coffee MUG--or a large Tim Horton's cup!!!