Why must warm up before oil change

[Tianmo]

I have been thinking about this logic.

 

Everywhere I check, I see ppl saying to warm up the car b4 oil change, because warm oil flow faster.

 

But...........................just wondering, wouldn't the oil still flow when it is cold? Will the oil flow out lesser if it is cold? will the oil flow out the same amount when hot or cold?

 

What happen if we change oil without warm up?

 

Lately I overfill my EO (itchy backside), and the only way to take out some oil was to change the oil filter, because my oil filter is located high up. I went to my WS and ask them to change a oil filter, and all the mech there was like blur , one took out the dipstick and told me that just nice because my EO level show more than half. But than there are oil in the engine, as in oil all over in the engine. When cold, it show more than max on the dipstick.

 

which means when we start engine and warm up, there are like about maybe 500ml of oil up everywhere in the engine, this oil will take some time to flow back down, if we change the oil when cold, would we be taking out more used oil?

 

is my thought logical or am I crazy?

[Tripthipal]

I think u have a point.. I really feel like testing it out on my car now

[GemLeo]

hi bro.. not sure what you mean exactly..

 

but i guess starting the engine.. to circulate the residue in the oil which has accumulate at one area when engine was stopped??

 

then it's more like getting more dirty stuff out from the engine.

[Trex101]

  On 11/29/2010 at 2:16 PM, Tianmo said:

I have been thinking about this logic.

 

Everywhere I check, I see ppl saying to warm up the car b4 oil change, because warm oil flow faster.

 

But...........................just wondering, wouldn't the oil still flow when it is cold? Will the oil flow out lesser if it is cold? will the oil flow out the same amount when hot or cold?

 

What happen if we change oil without warm up?

 

Lately I overfill my EO (itchy backside), and the only way to take out some oil was to change the oil filter, because my oil filter is located high up. I went to my WS and ask them to change a oil filter, and all the mech there was like blur , one took out the dipstick and told me that just nice because my EO level show more than half. But than there are oil in the engine, as in oil all over in the engine. When cold, it show more than max on the dipstick.

 

which means when we start engine and warm up, there are like about maybe 500ml of oil up everywhere in the engine, this oil will take some time to flow back down, if we change the oil when cold, would we be taking out more used oil?

 

is my thought logical or am I crazy?

 

Actually it's the time factor, warm oil drain dry faster then cold oil. The logic is that the mechanic will take less time servicing your car when warm compare to another car which is cold.

 

For me, when i DIY change my car oil, i usually let it drain for 30min or more while i clean the engine bay and other stuffs 1st before topping it up. If you DIY like me and have plenty of time, i think you can drain more oil if you let it drip for 30min - 1hr.

Edited November 29, 2010 by Trex101

[Tigershark1976]

i usually drain out the oil when the engine is cool.... dont want myself to get burn...

[ER-3682]

Inside the engine,there are many small grooves & holes,very difficult to drain 100% of the old oil....i would says,about 200-300ml[depends on the size of the engine],is still inside the engine.

[Crazecow]

Yes, warm oil drains alot faster compared to cold oil. Thats why people recommend you to drain oil while its warm. But becareful cause the oil is really hot.

 

When the oil is cold, you are right that you will be draining out more oil than when its hot. Cause when you leave the car overnight, the oil will flow back to oil pan, hence you will get more oil.

 

Actually, there is a way to make the oil drain slightly faster at the expense of new oil. When you are still waiting for the last few drops of oil to drip, just pour in some new oil. This way you don't have to wait till the oil pan is dry to get rid of the old oil. The new oil will clear out most of the old oil.

[Nightsky]

Liquid viscosity depends on temperature - at higher temperatures, oil tends to be less viscous, ie more fluid, therefore it is easier for oil to flow at slightly higher temperatures.

[Ben5266]

Maybe is because of the capillary effect. If the oil is less thick, capillary effect is less, hence it will drain faster and drain more.

[Tianmo]

  On 11/29/2010 at 4:02 PM, Tripthipal said:

I think u have a point.. I really feel like testing it out on my car now

 

 

test and feedback ok?

[Tianmo]

  On 11/29/2010 at 9:06 PM, Trex101 said:

Actually it's the time factor, warm oil drain dry faster then cold oil. The logic is that the mechanic will take less time servicing your car when warm compare to another car which is cold.

 

For me, when i DIY change my car oil, i usually let it drain for 30min or more while i clean the engine bay and other stuffs 1st before topping it up. If you DIY like me and have plenty of time, i think you can drain more oil if you let it drip for 30min - 1hr.

 

 

I also guess is the time factor.

 

I am going to DIY, but using the pump to suck from the dipstick.

[Tianmo]

bro, how much your amsoil going to increase after today huh?

 

payday on the 3 leh.

[Tianmo]

  On 11/29/2010 at 11:07 PM, Tigershark1976 said:

i usually drain out the oil when the engine is cool.... dont want myself to get burn...

 

 

more oil drained compare to warm? or the same?

[Tianmo]

  On 11/29/2010 at 11:19 PM, ER-3682 said:

Inside the engine,there are many small grooves & holes,very difficult to drain 100% of the old oil....i would says,about 200-300ml[depends on the size of the engine],is still inside the engine.

 

 

I understand.

 

just trying to get out as much as possible.

[Tianmo]

  On 11/30/2010 at 1:41 AM, Crazecow said:

Yes, warm oil drains alot faster compared to cold oil. Thats why people recommend you to drain oil while its warm. But becareful cause the oil is really hot.

 

When the oil is cold, you are right that you will be draining out more oil than when its hot. Cause when you leave the car overnight, the oil will flow back to oil pan, hence you will get more oil.

 

Actually, there is a way to make the oil drain slightly faster at the expense of new oil. When you are still waiting for the last few drops of oil to drip, just pour in some new oil. This way you don't have to wait till the oil pan is dry to get rid of the old oil. The new oil will clear out most of the old oil.

 

 

I actually saw 1 mech did this, brough 5L CL to the workshop, he poured in 1L towards the end as the oil was draining, stopped, and later fill up with the balance.

[Tianmo]

  On 11/30/2010 at 2:18 AM, Ben5266 said:

Maybe is because of the capillary effect. If the oil is less thick, capillary effect is less, hence it will drain faster and drain more.

 

 

But I was just wondering, how thin can the oil get after 20min of warm up?

[Hjgfdkjhretoilkjlkjlkj]

Yes, warm oil will flow faster as its thinner. Remember the viscosicity of oil is not measured at 100C

[Tigershark1976]

  On 11/30/2010 at 5:26 AM, Tianmo said:

more oil drained compare to warm? or the same?

 

 

same (from visual judgement). I drain the oil for the whole night so i dont think it makes any different...