I dont know what to do. Should I change my oil when its warm or when its totally cold?? Ive been changing my oil when its warm for years now, im just wondering what you guys think. Thanks.

 

i like to do it when its warm cuz the oil isn't as thick and you get more out of the motor when you do it that way IMO

 

ive always done it the opposite way. i have done it in the cold thinking that when its cold its has had time to drain to the bottom of the pan. not to mention avoid burning myself...i can be a clutz sometimes.

 

well this is what i do (should of said this to start with) i run the car till its at at running temp then turn it off and let it sit for 15mins then chage it... ( when its warm its not as thick and drains into the pan fast)

 

I usually change mine will cold so I know that more oil is in the pan as opposed to warm. But what My86Firebird said is a pretty good idea, cause whatever doesn't fall into the pan in 15 minutes, isn't gonna fall into the pan at all. But while were on the topic, what I USED to do, and will start doing again when I put my brand new motor in is..drain to the oil, refill, start up and let it run for 5-10 minutes, then drain it again, change the filter and refill and then done. If you haven't guess already, the idea is to run the clean oil through the motor to pull down any left over dirty oil film still clinging to internals. Gets pretty expensive though when using Mobil 1, lol.

Tom

 

I have heard convincing arguments for a couple schools of thought on the subject. Both of them have merit depending on the circumstances.

1. Drain the oil cold, so that the more viscous oil will help "plow" away any large chunks in the pan and direct them toward the drain hole. You'll leave a little more oil in the pan and engine, but all the large deposits will be cleaned out.
   
2. Change the oil hot, so that the greatest amount of oil will be drained, along with the greatest amount of suspended particles and grit. You may leave larger pieces in the pan, but the oil pickup screen will prevent them from being pumped into the engine.

If your engine has been neglected, or you suspect large deposits of "junk", and if you use a lubricant that doesn't clean as well (mineral oil), you may be better off changing it cold.

If your engine is relatively clean, and doesn't likely contain large pieces of carbon, gasket material, sludge, etcetera, then you may do better changing it hot so that all the oil and contaminant can be drained out. Since the engine was just operated, more particles are likely to be in suspension. The oil rushing out faster will tend to flush them out with the speed of the draining oil flow, rather than allowing them to settle out.

In either case, there are some conventions that apply to both situations:

• Cold oil will take longer to drain, and will cling to internal surfaces with a thicker film - leaving more old oil in the engine.
• Hot oil will drain faster, tending to wash away all the suspended particles but will also tend to run around large pises rather than push them out.
• Regardless of the oil you use, if it doesn't drain back into the pan within 15 seconds, you have a serious problem. If you think it takes 15 minutes for oil to drain back, you will be in deep trouble when you calculate that the oil pump takes 4 gallons a minute out of the sump at 3,000 RPM. If only five quarts take 15 minutes to drain back, you'll run out of oil in the sump in about six seconds. Better not drive much above idle speed if your engine does that.
• A lubricant that tends to clean better will likely have more contamination (look dirty) than a less detergent oil.
• The air filter is possibly more important than anything in maintaining a clean engine. Oil analyses of drained engien oil show that most of the particulates and contaminants in an otherwise correctly tuned engine are from atmospheric dirt. All that dust that is sucked into the engine needs to be trapped in the air filter, or it will end up stuck to the cylinder walls and be washed/scraped away by the piston rings - right back into your oil sump.
• The oil filter is critial in the entire cycle. A good filter that has adequate element surface area to trap particles and still alow full flow will keep the engine cleaner. Once the filter goes into bypass mode, it is useless.

It's crucial to use a good filtes.

Personally, I always change mine hot. I also have never had an engine of mine torn down for a lubrication failure. Usually, my teardowns are completely for recreational (improvement) purposes. I've had almost 200,000 miles on more than one Chevy engine, and until I get less satisfactory results, I'll probably continue to follow the procedure I've always used.

 

Depends on the outside temp. If it is hot outside, do it with the engine cold, if it is cold outside, warm the engine and allow to cool to where the oil won't burn you.

 

Thank You very much Vader for the detailed description! That helps a lot. Thanks again!

 

I change mine warm...Gets more crap out of there...I change my oil alot too...

 

i change mine usually after running the car up to normal temp, and then i park it get everything ready and after some minutes has gone by i go to work.

around every 3,000 miles with mobil 1 and a puralator filter.

 

I change mine cold so I don't burn myself. I change the oil (and filter) often enough so I don't think it matters. Hell if I wanted all the old oil out of there, I'd be tearing the motor down every few months.

Well I guess technically I don't change it cold... I let the motor run just long enough for me to get the car into the garage and positioned for jacking it up. So that's maybe, what, 1 minute?

 

No oil pan will drain completely. The nut for the drain plug is inside, so there is no way gravity is going to drain that last 1/2" or so (the canted plugs are a little better about that than those mounted flat to the bottom of the pan).

When cold, more "junk" will have settled out of the oil. Guess where it settles?

For that reason, I'm an advocate of draining the oil warm. More of the particulates that may be in the oil, that are too small for the filter to take out, will be suspended in the oil that way. Since the typical pleated paper filter lets things smaller than 60 microns go through (that's about .004"), it would be better to have that stuff suspended when the bulk of the oil is drained, than settling out and staying there for the fresh oil to pick up.

If you have stuff big enough to need the "push" of the extra viscosity of cold oil, you've probably got more problems than deciding whether to drain the oil cold or warm.