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The idea is that oil is less viscous when warm and flows out a little better. The dirt also becomes suspended in the warm oil, instead of just laying on the bottom of the pan or in the oil galleys.
Bottom line is, you just get a better drain if the oil is warm or hot.
For the past few oil changes, I've used Mobil 1 0w40 European Formula, full synthetic. Towards the end of the oil change cycle, I've noticed I get this bright buildup on the inside of my oil cap, a smooth, firm, dry residue ranging from Corvette red to stop-light yellow. It's never been wet to the touch, and has only been present as of late.
Should mention this is in the first generation Hemi magnum 5.7L engine. No operating issues, but I just want to know what this is.
Are you making short trips, say less than 5 miles, frequently?
There's a secondary reason for "warm" oil, and that's to suspend any particles that may have settled, back into the oil/in suspension so it drains out with the oil. The lift I use is 5 miles from my driveway, which is the perfect distance to have a warm, but not hot, engine.
All told, the fact that the oil is changed is more important than if it's hold, warm or cold. It's also more important than if you do a 5 minute or a 5 hour drain.
There's a secondary reason for "warm" oil, and that's to suspend any particles that may have settled, back into the oil/in suspension so it drains out with the oil. The lift I use is 5 miles from my driveway, which is the perfect distance to have a warm, but not hot, engine.
All told, the fact that the oil is changed is more important than if it's hold, warm or cold. It's also more important than if you do a 5 minute or a 5 hour drain.
Yeah, concur. Oil should be changed when warm.
A. Because it flows better, regardless of the rated weight.
B. Because any sludge will be in suspension, rather than settled. (This was more important back with non-detergent oils, but it is still good advice. The nastiest stuff in the oil settles. If you change it cold, you are more likely to leave residue than if you change it warm. That residue includes metal shavings and bearing material shavings.)
C. I also agree that it is more important, given the quality of most oils these days, that the oil is changed, period. Back in the day of non-detergent oils, you might have a little slack - better to change warm at 4K than cold at 3K - but non-detergent oils saw significant residue from metal and bearing material wear.
Fairly hot oil drains more thoroughly, not just faster. I’ve changed it cold, warm and hot. The amount that drains out in a given period of draining is directly related to increasing temperature. I do not rush the draining, nor do I give it hours to drain. Generally, I wait from 20 to 30 minutes before putting the plug back in.
If I want to change the oil and the vehicle has been sitting undriven for more than a few hours, I will either run the engine for a few minutes OR I put a small space heater under the oil pan (for maybe 30 minutes) so that the oil is a little bit warmed up. Best thing is to change the oil shortly after returning from running an errand with the truck, but sometimes there is too much to do so I end up changing the oil on a less busy day. Because I change the oil myself at safe intervals of miles and time, I’m not too worried that sometimes the old oil is warm rather than hot.
Some of the comments do not make logical sense to me. more viscous (cooler) oil will carry the derbis better than thinner (less viscous - hot) oil. It will settle out of less viscous oil more readily.
There is no problem with getting oil to flow out no matter the temperature. It does not need to be hot to flow out. Gravity works the same at any temperature. It is still liquid and will eventually all drain out. The difference in time is a matter of a few minutes.
If the vehicle has been run recently, the oil will be distributed more throughout the engine and not collected in the pan. Thus, when you drain the oil hot, you need to drain longer to get all the oil out. At least that has been my experience with several vehicles. I no longer change oil at home (disposal effort is not worth the $12 savings), so it has been a while. Maybe newer cars work differently and trap less oil in the engine immediately after running it.
The difference in viscosity is minuscule. It is not enough to make much of a difference one way or other. The oil is still liquid. Unless you have run it to sludge, hot or cold is nto gong to make a meaningful difference.
I am wondering whether the people who say it is critical to change the oil hot, also put nitrogen in their tires.
Some of the comments do not make logical sense to me. more viscous (cooler) oil will carry the derbis better than thinner (less viscous - hot) oil. It will settle out of less viscous oil more readily.
"more readily" still takes time, less time, but it's not instant. There's a Potential to get more debris out, less that sticks to the bottom of the oil pan.
Quote:
Originally Posted by Coldjensens
If the vehicle has been run recently, the oil will be distributed more throughout the engine and not collected in the pan. Thus, when you drain the oil hot, you need to drain longer to get all the oil out. At least that has been my experience with several vehicles. I no longer change oil at home (disposal effort is not worth the $12 savings), so it has been a while. Maybe newer cars work differently and trap less oil in the engine immediately after running it.
Careful about that "$12 savings", it's easy to turn that into a stripped out oil pan, leaky plug, and the worst I've seen was a plug that was pushed out (PCV clogged, pressurized crankcase) that dumped all the oil and seized the engine. I've seen too many that were gooped up with JB Weld and cost the owner no tiny sum to get it fixed right. Some oil change places are good, but how do you know which ones? A dealer can hire a gorilla without sense just as easily as the jiffy-mart oil drop.
But, the point I wanted to get to is that modern vehicles all seem to have you check the oil about 10 minutes after engine stop. That would indicate to me that at 10 minutes, all the oil that's going to drain, will have drained.
As I said above, what's important is THAT the oil is changed. Hot, warm or cold is irrelevant, subject to personal taste. I do mine warm because I'm not a fan of burning myself and don't have the means to do it in my driveway/have a 2-post lift just a few miles away.
Quote:
Originally Posted by Coldjensens
I am wondering whether the people who say it is critical to change the oil hot, also put nitrogen in their tires.
Everyone puts in at least 78% nitrogen. Apparently the above is so prevalent that Mazda issued a TSB with:
Nitrogen for tires • Compressed air contains approximately 80 percent nitrogen.
• There is no practical value added from filling tires with nitrogen.
For the past few oil changes, I've used Mobil 1 0w40 European Formula, full synthetic. Towards the end of the oil change cycle, I've noticed I get this bright buildup on the inside of my oil cap, a smooth, firm, dry residue ranging from Corvette red to stop-light yellow. It's never been wet to the touch, and has only been present as of late.
Should mention this is in the first generation Hemi magnum 5.7L engine. No operating issues, but I just want to know what this is.
Kinda like this?
If that looks similar, google "engine varnish" and some of the causes.
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