0w-20 oil -- need to warm it up before oil change?

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Steve ... When your car is cold ... the oil is “0” (water thin). When your car is hot ... the oil is “20” (more viscous than water but still really thin).


NO. ... “W” does NOT mean “water”.

... But I’m just sayin’. ​

 

I've tried it both ways and I no longer think it is worth a warm-up drive in advance.

 

It doesn't hurt anything to let it run for a couple
minutes anyway. On the same topic - seems I read that the multi-viscosity thing - about making the oil feel thinner when it's warmer vs. Colder, is a misnomer but idk.
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I too am concerned about such a low viscosity for engine oils. I wonder if the longevity of the engine is sacrificed for a minimal increase in MPG ratings.

This is a pretty good explanation of oil viscosity.

When you see a W on a viscosity rating it means that this oil viscosity has been tested at both a high and low temperature. The numbers without the W are only tested at 210° F or 100° C which is considered an approximation of engine operating temperature.

In other words, a SAE 30 motor oil is the same viscosity as a 10w-30 or 5W-30 at 210° F (100° C). The difference is when the viscosity is also tested at 0° F or (-18° C).

For example, a 5W-30 motor oil performs like a SAE 5 motor oil would perform at 0° F (-18° C), but still has the SAE 30 viscosity at 210° F (100° C) which is engine operating temperature. This allows the engine to get quick oil flow when it is started cold verses dry running until lubricant either warms up sufficiently or is finally forced through the engine oil system. The advantages of a low W viscosity number is obvious. The quicker the oil flows cold, the less dry running. Less dry running means much less engine wear.

This is accomplished by adding additives to the oil. Some additives thicken the oil at operating temperatures while others lower the viscosity at low temperatures. As you put miles on the oil, these additives evaporate off so the oil loses those properties.

 

You don't "need" to have the oil hot to drain it out.
But having it warm can't be a bad thing.

 

Ever the contrarian, I usually go the other way....

My 3 adult sized vehicles (all use 5w30) have over 150,000 miles, and I prefer to change the oil with the engine dead cold, preferably after having been parked all night. This allows me to ensure that all of the oil has made its way back into the sump and gives me a realistic idea of whether or not I'm using a measurable amount of oil between 5k changes.
My baby ute (GMC Terrian) uses 0w20, and "warming" the oil to make it thinner is an absurdity, IMHO.
I changed the oil just yesterday and was pleasantly surprised how clean it was.
Since we had used the vehicle that morning to <<**trigger alert!!**>> go to church, my normal method wasn't applied, and I had to settle for a fairly warm motor.
For the Covid Karens we're doing "drive-in, contactless church" until Delta eases.

SO....
Back in the day when people used molasses-thick oil in primitive, hand built, iron engines I suppose you had to heat it up to ensure that most of it had a chance to ooze back into the sump.
Back in the 'good old days' we also used relatively raw dino-lube with a 3000 mile oci in hulking, inefficient 5 liter engines that, *maybe* made 300BHP, and sometimes managed to stay in operation for an eye-popping 100,000 miles.
Speed limits were 55mph, the average fuel economy was in the teens, and despite their relative up-armouring many of these "old school" vehicles weren't much safer than the bantam-weight, plastic-on-stamped metal, crumple zoned cars we have today.

That's why only idiots would want to go BACK to...."the good old days."


Thus, absenting a good reason to do so...I don't feel particularly bound to "always do it because we always DID it."
I'm "old school" about many things....but it IS A SCHOOL.

 

Even when it "flows like water", the viscosity of the oil is still way higher than that of actual water. As for the OP question, why did you change the oil after after warming the engine? So it can drain better? Being hot or cold likely isn't going to make much difference. There is another reason to run the engine first though. To ensure all the free particles are in suspension, and as little as possible are left sitting at the bottom of the pan.

 

My car has an oil filter.

 

The pursuit of efficiency also means tighter clearances between engine parts. Using a thicker oil means it flows slower between those parts, increasing overall oil pressure, and possible not getting 100% coverage.

The 'cold' oil viscosity test is dona at 40C(104F).

Which clogs up, and opens the bypass valve in about 1000 miles.
What darkens the oil with use is a build up of suspended particles.

 

Oil gets dark?

Hmmm
I guess I need to keep my 5K OCI.....
Don't want that to happen to ME.

Besides....my cars also have oil pressure gauges.

 

My favorite way to change oil is a long drive home lasting hours and then straight up onto ramps and drain soon as I arrive. But many times, especially in winter that's not practical.

As for 0W-20 issues, I can relate... Just after an oil change its so clean you can barely see it on the dip stick.

 

Glad to see that you are living up to your handle once again.
Both of those statements are total BS.

 

Then what causes the oil to darken?

 

Sure am glad you learned to properly hold your dipstick because if you hadn't of mentioned that part my inner troll would of had to much to say to you!

 

The main bearing, rod bearing and piston to wall clearance of a Prius V engine are nearly the same as my 1972 Pinto 2 liter engine was 50 years ago.

The 0 in the 0W20 means that it will get to the bearings a little sooner during a startup than the recommended 10W30 did in the "good ol days".

 

The 'polishing' of the Prius v engine means the microscopic crevices in the cylinder wall are a lot shallower. Those there might actually be on purpose to help reduce friction.

The 20 means the oil flows easier at operating temperature. Carrying away any particles and soot quicker.

 

Petroleum based oil naturally darkens with heat.
Automotive oils darken because of changes in the additive package.
IF.....your oil gets black because of suspended solids, you have a serious problem.
And so does the engine.

What Causes Black Motor Oil? Is it a Bad Thing?

 

It’s not that hot. And it gets a chance to come off the peak temp, if you’ve spent some time getting out stuff and raising the car.

I typically don’t go out of my way, say drive the car just to warm up the oil. Instead I’ll do the change when we just got home, say after a bit of shopping. Get it raised, engine underpanel removed, oil catch system in place, remove drain bolt, go in for dinner or tea.

then come back out, deal with the oil filter, button everything back up, lower the car, pour in spec qty of oil.

if it wasn’t convenient to drive beforehand it’d be fine too, doing the drain cool, but all things being equal, might as well do it hot.