adallak Posted October 11, 2011 Report Share Posted October 11, 2011 I have always changed oil when it was hot. The hotter the thinner so it is faster to drain. On the other hand, if the car was sitting over night, more oil was drained into the pan, so potentially you will get more used oil drained, say in the same 30 minutes. There is a theory though, that some suspended particles will settle in the pan and probably will not get out with the volume of oil if you you let the car sit over night before changing oil. The drain plug on my oil pan is positioned so that about a half of pint of oil will stay in the pan no matter what. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Texas Jim Posted October 11, 2011 Report Share Posted October 11, 2011 I have always changed it hot... For the reason you mentioned... a lot of the stuff that is suspended in the oil when it is hot and circulating in the engine, may settle out and not get drained out of the engine. BUT...if the filter is doing it's job.. how much stuff is actually still in the oil ??? I would venture a guess of very little... But I will continue to change it when it is hot... it just eases my mind a little more... even if it really makes no actual difference. :D Link to comment Share on other sites More sharing options...
hjb981 Posted October 11, 2011 Report Share Posted October 11, 2011 I would change it hot. There will always be particles that are too small to be caught by the filter - it has to have a threshold at some level. Of course those small particles will also be the ones staying in suspension the longest. As for draining from the engine to the pan, most of it happens right after you shut off the engine, when it is still hot. When I check my oil level, it reads a quart lower if I check it right after engine shut-off. If I wait 5 minutes, it will be at its normal level, and after that I do not see much change, so not that much happens after 5 minutes. (If I wait until the car completely cools down, the oil level will go down a quart again, because of the oil's contraction.) The much higher viscosity of cold oil when draining from the pan will probably retain enough oil on the walls of the pan that you actually get less oil out by changing it cold. Therefore you would have to wait a long time, and then you may as well change it hot, since then there would be time for the oil to drain from the engine to the pan, and then out, anyway. Link to comment Share on other sites More sharing options...
navion Posted October 11, 2011 Report Share Posted October 11, 2011 I have always changed oil when it was hot. The hotter the thinner so it is faster to drain. On the other hand, if the car was sitting over night, more oil was drained into the pan, so potentially you will get more used oil drained, say in the same 30 minutes. There is a theory though, that some suspended particles will settle in the pan and probably will not get out with the volume of oil if you you let the car sit over night before changing oil. The drain plug on my oil pan is positioned so that about a half of pint of oil will stay in the pan no matter what. I also vote for changing the oil hot. I do it on everything from aircraft to large diesel engines. And to add another aspect, if possible I will schedule an oil change so I can drain it in the evening and let it drain all night. Then the next day, I will prefill the filter, replace the drain plug and add the correct amount of oil. Just don't forget and have someone drive off with no oil! That would NOT be beneficial. Britt Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 11, 2011 Report Share Posted October 11, 2011 I agree, hot, it runs faster Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
KHE Posted October 11, 2011 Report Share Posted October 11, 2011 Always change the engine oil hot. What little oil may remain is not worth worrying about. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
adallak Posted October 11, 2011 Author Report Share Posted October 11, 2011 Well, for the first time I have decided to change it cold. Got out about 1/2 qtr less than usual. Now it is about 1/4" above the highest hole in the dipstick... Should I drain the excess or leave it alone? The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Texas Jim Posted October 11, 2011 Report Share Posted October 11, 2011 Just my opinion... but as long as it is not over the "FULL" mark... I would leave it alone... Link to comment Share on other sites More sharing options...
adallak Posted October 11, 2011 Author Report Share Posted October 11, 2011 Just my opinion... but as long as it is not over the "FULL" mark... I would leave it alone... It is about 1/4" higher than the "operating range" mark. By the way, because the drain plug is on the driver side of the pan, I lift the passenger side up to get as much oil out as possible. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Texas Jim Posted October 11, 2011 Report Share Posted October 11, 2011 Just my opinion... but as long as it is not over the "FULL" mark... I would leave it alone... It is about 1/4" higher than the "operating range" mark. It will probably be fine... if the engine don't like it that full, it will use it in pretty short order. But if you are as anal about your car as I am... I would probably take out just a little bit... You may be able to get a small hose down the dipstick hole and siphon a little out... may save getting back under the car. Link to comment Share on other sites More sharing options...
adallak Posted October 11, 2011 Author Report Share Posted October 11, 2011 Just my opinion... but as long as it is not over the "FULL" mark... I would leave it alone... It is about 1/4" higher than the "operating range" mark. It will probably be fine... if the engine don't like it that full, it will use it in pretty short order. But if you are as anal about your car as I am... I would probably take out just a little bit... You may be able to get a small hose down the dipstick hole and siphon a little out... may save getting back under the car. Will drain a pint in a couple of days. Hate to make a mess in the engine bay. Yeah, I am probably as anal about my car as you are about yours. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Ranger Posted October 12, 2011 Report Share Posted October 12, 2011 I change mine hot for flowability reasons. Link to comment Share on other sites More sharing options...
adallak Posted October 28, 2011 Author Report Share Posted October 28, 2011 For the first time, changed the motor oil cold. Will not do that again because I got less old oil out of pan than usually. Sure, I would get the same result if I waited for 24 hours, but who is going to wait for so long? The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
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