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Oil Won't Drain Completely... 😮‍💨

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#21 ·
I call BS on all three of Motortrend's "Expert" opinions.

MT 1. Oil viscosity is thinner when it's hot, so it drains more quickly and completely out of the engine than when it's cold.
As Tazio says:
Tazio Nuvolari said:
--from the real old days of single weight non-detergent oils. Those 30w and 40w oils were very thick and slow to drain when the engine was cold--
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Current oils are as thin as water. Maybe MT's experts are from that bygone oil era.

MT 2. On a hot engine, contaminants are more likely to remain suspended in the oil than when the oil is cold, increasing the chances they'll be expelled from the engine during the draining process.

I thought modern oils had detergents and additives specifically designed to dissolve contaminates and keep them suspended regardless of temperature. If they weren't they'd be the first particles or whatever these contaminates are to come out upon removing the drain plug. Again that may have been true with the old non-detergent single weight oils.

MT 3. Today's high-tech OHC engines hold oil in a lot more places compared to old-school motors, so it's gotta be warm (and thin) to escape from all those upper-end crevices.

What? So today's pushrod high-tech engines like many of the V8s don't have these mysterious crevices? Must be okay to drain them cold. And please show me a diagram of where these crevices are that can magically retain oil even after given overnight to drain.

But I do have a one-size-fits-all solution. Pull the plug with the engine warm and let it drain overnight. Would take care of any viscosity oil, all possible suspended contaminates, and keep those crevices retain free.
 
#22 ·
Your transmission fluid is drained when it is cold and I think there are more contaminants in it than there is oil. Otherwise there wouldn't be magnets in there. Along with being tighter crevices, such as in the valve body. If you drain it hot, you're going to have to let it sit a long time to cool back down to set the proper level being it is set within a low temperature range, unless you have the tool to set at any temperature.
 
#23 ·
Robert70 said:
When draining the oil cold a lot of the oil stays stuck inside the drain pan. That's why they say to drain the oil when hot. You also need to consider different brand of oil filters some are larger/smaller in size causing different quantities of oil needed. Change Engine Oil Hot … Or Not? (motortrend.com)
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??? Their conclusion: Drain engine oil hot, and let the car sit and keep draining for at least a half hour. Wear mechanic's gloves to minimize the chance of getting burned.
 
#24 ·
All engines have old oil left which means you are diluting it with the new oil. Most of the contamination is fuel related. They want the engine warmed up to ensure the top end and timing chain remains lubricated on startup when the filter and oil pump may take a few extra seconds to move the new oil. No one at the dealer or oil change places prefill the new filter.
 
#25 ·
rj.parker said:
They want the engine warmed up to ensure the top end and timing chain remains lubricated on startup when the filter and oil pump may take a few extra seconds to move the new oil.
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So you're saying they don't want the old oil to have time to fully drain off the parts.
rj.parker said:
No one at the dealer or oil change places prefill the new filter.
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It's a lazy man's hedge against lack of startup lubrication due to not prefilling.

Sounds like trying to get away with not doing the job right. Brilliant!
 
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#26 ·
Dr. Dyno said:
So you're saying they don't want the old oil to have time to fully drain off the parts.

It's a lazy man's hedge against lack of startup lubrication due to not prefilling.

Sounds like trying to get away with not doing the job right. Brilliant!
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Think of it as a fool-proof method, needed because so many fools are changing oil. If you know how to do it proper, go ahead; otherwise use the simpleton method.
 
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#27 ·
Dispersants keep everything suspended in the oil. Some are lost in the 1800's lubrication misinformation.

The only difference between a hot or cold oil drain is TIME needed for the same effect. The amount of oil in the pan doesn't make a difference concerning oil temp. The big issue is the front-only ramps one should use, and the pathetic recessed/angled/placement drainplug location that most automakers spec for the oil pan.

Has nothing to do with 'start up' lubrication. There will always be a film of oil on components, even after sitting overnight. And, ADBV's tend to leak slowly so filter is usually empty after a few days. We don't go all nutso worrying about lubrication because we left the engine off overnight or over the weekend.

Prefilling filter, even 1/2 or 1/3 way is attention to detail. So, if you fear startup lack of lubrication, then prefill your filter. When I worked in filter manufacturing, dry media was the easiest to damage. So, I prefill the filter to make sure that my filtration media is saturated to prevent it from being a dry wall for the 1st wave of oil flow.

Concerning motortrend, I don't expect much from non-mechanicals writers. Being a writer doesn't make you a mechanic.

From MT:
  • Oil viscosity is thinner when it's hot, so it drains more quickly and completely out of the engine than when it's cold. This is rocket science. I have plenty of time. Your quicklube dealer doesn't. I'll take a 12ounce and sandwich break. I doubt anyone lets it drain for 1/2 hour as MT recommends. The draining time at the dealer is usually the R&R filter service time, or simply the drainplug gasket replacement time.
  • On a hot engine, contaminants are more likely to remain suspended in the oil than when the oil is cold, increasing the chances they'll be expelled from the engine during the draining process. And, when not suspended by the oil's additive package, where do they hide? Again, ol' school thinking that magical Houdini contaminants hide and don't drain out. There's probably 5x more dispersants in your oil than antiwear additives, especially when considering those foolish OLM and 10k+ intervals greenie automakers are pushing. I have more faith in the dispersants than I do in MT's recommendations.
  • Today's high-tech OHC engines hold oil in a lot more places compared to old-school motors, so it's gotta be warm (and thin) to escape from all those upper-end crevices. So, did those secret hidden crevices not drain down to the pan while I let the engine sit over night? WTF is wrong with these yahoos.
  • English/communication writers shouldn't be giving mechanical advice, or quoting their so-called experts .
  • Bottom line, don't take advice from MT
Gotta run. The upper-end crevices and I are about to do battle.
 
#28 ·
My thoughts exactly. ;) Thanks for typing them up for me.
 
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#29 ·
Are we actually going to do this again? As for the OP, 5 times in less than 30k? You're throwing out perfectly good oil.

If you warm the engine, turn it off and let it sit for 10 minutes, you'll get the vast majority of oil out - which is the point. There will always be oil left over and that is fine. Me thinks a lot of you are way, way overthinking things.
 
#30 ·
Regarding oils (not) thinning as the engine gets hot - a 5w-15 oil is 5 when cold and thickens to 15 when hot. There are molecules in the oil that uncurl as they heat up and increase it's viscosity. This helps the oil flow at engine startup and helps it protect once up to temperature. Afaik we change the oil hot to make sure all the crap is suspended in it and hasn't settled out.
 
#31 ·
Good post Greasy

I drain oil after it has been sitting over night because I don’t want to deal with hot stuff. I figure that it will just take a little longer until the dripping stops. I’m in no hurry. If there’s any less drained, it will be such a small amount that is not enough to make a difference.

What I noticed on my RAV4 is the location of the drain plug and design of the oil pan will retain quite a bit of oil. Maybe a quarter of a quart. This has been the case on most cars that I have worked on.

Bottom line: It doesn’t matter. There is nothing that you can do about it. Don’t worry about it.
 
#32 ·
A8k said:
Regarding oils (not) thinning as the engine gets hot - a 5w-15 oil is 5 when cold and thickens to 15 when hot. There are molecules in the oil that uncurl as they heat up and increase it's viscosity. This helps the oil flow at engine startup and helps it protect once up to temperature. Afaik we change the oil hot to make sure all the crap is suspended in it and hasn't settled out.
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Wrong

Oil is thicker when cold than hot. You can prove that yourself using your refrigerator and stove/microwave. Some ol' school BS that you posted.
 
#34 ·
Hey OP…Funny that you didn’t get all your oil out of the car because I jacked the front end up and drained mine two weeks ago. The previous change was done at a quick lube place in town and guess what?? I barely fit the drained oil into the 5 empty bottles I had from my Camry oil change(each one was filled to the neck or higher). Those guys must have put 5+ quarts in the car last time or they didn’t get the oil drained all the way. So if keeping the car flat doesn’t allow a full drain that could explain why I had extras.
 
#35 ·
#36 ·
SAE J300 prefix/suffix system. This is what the bottle grade means as seen in the attached photo. I'd ignore the newbie. Not sure if its a bot/ai/troll or even has a rav4. There are many trolls ruining forums everywhere, especially with clueless misinformation. If it is not on the SAE J300 system, then it needs to be defined by the seller/blender/brand.

Image
 
#37 ·
I believe there is confusion because most people will associate "cold" with room temperature. Cold being 40C (104F) is a foreign concept.

Then throw the concept of a multi-weight oil with the characteristics changing over temperature...
 
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#38 ·
#39 ·
Just for a laugh. Google up what the 'W' stands for. We had a laugh at work about this the other day. Oil threads are the best threads!! LOL
 
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#40 ·
Widgets said:
I believe there is confusion because most people will associate "cold" with room temperature. Cold being 40C (104F) is a foreign concept.

Then throw the concept of a multi-weight oil with the characteristics changing over temperature...
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It’s always been my understanding that the W number means the oil will thicken as much as a straight weight oil of that number when cold and will thin as much as a straight weight oil of the second number when hot. The reason it’s called a “multi weight” oil.
 
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