Changing engine oil (Hot or Cold)

Submitted: Friday, Feb 21, 2003 at 17:56
ThreadID: 3482 Views:2215 Replies:10 FollowUps:3
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Conflicting ideas on wether to change the oil when engine is hot or cold as when the engine is hot the oil is thiner and drains beter but the oil is still draining from the head ect.

What do you guy's do ?

Kev.
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Reply By: diamond - Friday, Feb 21, 2003 at 18:18

Friday, Feb 21, 2003 at 18:18
when i service cars i run them first to get oil hotter for reason above thinner oil
AnswerID: 13677

Reply By: David - Friday, Feb 21, 2003 at 18:27

Friday, Feb 21, 2003 at 18:27
Change it hot but don't burn yourself-
A good compromise would be to change it when warm...
AnswerID: 13682

Reply By: Suzuki Viagra - Friday, Feb 21, 2003 at 18:41

Friday, Feb 21, 2003 at 18:41
Hot - more oil runs out.

If you have tough hands then it's ok, but otherwise wait 2 beers and it'll be uncoimfortable but wont burn....

As an ex mechanic your skin gets used to it - but your wife don't get used to the grease stains on everything.......
AnswerID: 13688

Reply By: Gary - Friday, Feb 21, 2003 at 19:00

Friday, Feb 21, 2003 at 19:00
Always hot, the oil will flow quicker. Just wait a few minutes extra to allow the oil in the top end to trurn to sump
AnswerID: 13692

Reply By: Truckster - Friday, Feb 21, 2003 at 22:21

Friday, Feb 21, 2003 at 22:21
NOT HOT!!!!!! REPEAT NOT HOT...
Dont come back from a day trip and jump under the car...

Again NOT COLD....

Hot will burn you to the bone if it hits your arm as you remove the plug.

Cold will be too thick... Warm is the go... Run it for 3-5 odd mins at idle.....

Warm oil is thinner and runs our easier....
AnswerID: 13715

Follow Up By: Kev. - Friday, Feb 21, 2003 at 22:30

Friday, Feb 21, 2003 at 22:30
I take it you mean not to hot !!

The last thing i want to do after a day trip is change the oil , keep me buzzy on the weekend.
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FollowupID: 8106

Reply By: Bob Y. - Saturday, Feb 22, 2003 at 15:50

Saturday, Feb 22, 2003 at 15:50
Kev, We always run vehicle up to normal operating temp, or drain oil on return home after day's work. Have the luxury of drive on service ramp, so often leave vehicle to drain overnight. Don't know if I'd be too keen to get under hot vehicle, if had to do it goanna style! Hot is best for diesels, as their oil often gets "gluggy" towards end of oil change interval. Have plenty of work shirts, with "shrapnel marks", from removing plug, on very hot sumps. Hooroo...
AnswerID: 13743

Reply By: nugget - Saturday, Feb 22, 2003 at 23:14

Saturday, Feb 22, 2003 at 23:14
Draining your oil hot is better as it flows easier and also because contaminants in the oil are in suspension because your engine has just been run. If you would then leave you oil to cool down eg overnight before draining, then some contaminants will seperate from the oil and be left behind in you engine. Drain your oil straight away after it has been run.
AnswerID: 13760

Reply By: Member - Bob - Sunday, Feb 23, 2003 at 08:25

Sunday, Feb 23, 2003 at 08:25
I might be missing something here, but.... When the engine is cold didn't the oil spend several hours dripping down from the upper galleries etc from when it was last hot? So the only places in a cold engine that contain oil are the filter canister and the sump? If you crank the motor you send cold oil everywhere, and then have to wait for it to slowly return to the sump. The sump plug is big enough for it not to matter whether the oil is thick or thin. So I reckon, provided you don't crank the engine, you will retrieve more old oil and crud from a cold engine.
AnswerID: 13761

Follow Up By: Kev. - Sunday, Feb 23, 2003 at 15:31

Sunday, Feb 23, 2003 at 15:31
Thats basicly the question i asked.
When cold the oil has had time to drain from the engine, if you check your dipstick after a run it can take several hours for the oil to reach the cold oil level.

Best idea may be to drain while hot and to leave overnight if possible.
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FollowupID: 8185

Reply By: Coops - Sunday, Feb 23, 2003 at 08:35

Sunday, Feb 23, 2003 at 08:35
I've always done it when hot for the thinner oil reason but have never really thought that it would matter significantly.
AnswerID: 13762

Follow Up By: Bruce - Sunday, Feb 23, 2003 at 18:56

Sunday, Feb 23, 2003 at 18:56
Like many others I believe it is definitely best to drain oil when hot/normal operating temp but you must let it drain for a long time eg several hours or overnight if possible, this way you can as much out as is possible.
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FollowupID: 8193

Reply By: Bruce - Sunday, Feb 23, 2003 at 19:04

Sunday, Feb 23, 2003 at 19:04
I forgot to add that you also need to ensure the vehicle is parked at the right angle to let all the oil drain out the plug hole. On some vehicles this means running one or both wheels part way up a ramp.
AnswerID: 13789

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