Why specifically use 5w30 when you could just use 0w50 grade engine oil for all cars?

[Ohiocruiser]

I'm not saying to wait until full operating temp, but to minimize load at the most extreme temp. There's probably a diminishing return as you get further from ice cold, but it's hard to imagine a few minutes and 50-100 degree head start before putting a load on the engine isn't preferable...

Well, that's why I keep it under 1500 rpm first 5min, maybe little longer. I doubt it stresses the engine.

 

[Thomby]

Well, that's why I keep it under 1500 rpm first 5min, maybe little longer. I doubt it stresses the engine.

Fair enough, we're probably arguing shades of grey at this point. Maybe the thing to do is something similar to what @D.J. did above, and plot time vs. idle oil temp for various ambient temps, and compare to a startup and light drive.

 

[Ohiocruiser]

I mean, you gotta love all these oil threads. Should we start arguing about which brand is better already?

 

[D.J.]

Fair enough, we're probably arguing shades of grey at this point. Maybe the thing to do is something similar to what @D.J. did above, and plot time vs. idle oil temp for various ambient temps, and compare to a startup and light drive.

For science, I do plan on hopefully getting 2 similar days (temperature) to compare: the 2 scenarios.

Today, the ambient temperature was 0°C (I don't control the weather)
After 9 hours of being parked outside at my work, my oil and coolant temps were not at 0°C. They were closer to 12°C despite sitting outside - odd.

From 6:17 to 6:27, I was not moving.
~6:28 my TPMS detects as I started driving
You can clearly see where I start driving based on the intake air temperature fluctuating.

 

[Volfy]

It's not just the piston speed, but also the side load on the major thrust face. It's why cylinders wear into ovals. You don't think this will occur at a higher rate when the oil is 150 degrees below its operating temp and you have a load sufficient to accelerate the car's weight? Vs. nearly zero load?

This is a valid concern. It is also why many engines have the crank pin offset slightly from the cylinder centerline, such that the power DOWN stroke (which is when the piston side thrust is at the greatest) sees less crankpin offset than the compression UP stroke.

Now then, just because there exists piston side thrust doesn't mean there will be wear on the opposing cylinder wall. If that is the case, then the engine will be destroyed in no time at all. We all know that is not the case. Why?? Because thin film lubrication by circulating engine oil provides a cushion between the piston skirt and the cylinder wall. Same as at any bearing surfaces. The two opposing metal surfaces actually glide on a thin film of oil, such that no metal-to-metal contact actually occurs.

What produces frictional heat is actually work done in shearing this thin film of oil - not dry contact friction. More side thrust adds more stresses, which produces more frictional heat, not necessarily more wear... so long as the thin film lubrication is maintained.

So... what provides this thin film of oil, you ask? Why, the engine oil pump, or course. This gets at the crux of why driving gently is preferrable to idling. With the car driven gently and the engine operating at moderate RPMs (say between 1500 and 2000 RPM), the direct gear-driven oil pump will be pumping more rigorously to produce a healthy oil pressure - and flow - compared to when idling. This is absolutely critical, especially when oil at low temp is more viscous and thus harder to flow effectively through tiny oil passages. Again, as long as thin film lubrication is maintained - and the driver doesn't go nuts with the loud pedal - the engine will warm up faster and get out of the danger zone sooner, all the while protected by a robust oil circulation.

Now, if instead you choose to idle. RPM will be low and the oil pump will be driven at the absolute slowest RPM. Now, if you check the oil pressure reading, it might actually read reasonably high, depending on where that oil pressure sensor is located. This might mislead you into believing you have adequate oil pressure and flow. Well, because the oil at low temp has higher viscosity, it tends to resist pumping, so the oil pump needs to push that thicker fluid harder. This might register an adequate pressure reading at the oil pump outlet, but that pressure will quickly drop when the oil has to flow through tiny orifices and small passages. So, by the time that oil reaches the bearing surfaces, there might not be much pressure left to produce a robust enough thin film strength.

Ironically, NO load doesn't necessarily guarantee NO wear. This is an easy misconception to theorize, by those without a solid understanding of tribology.

 

[rtv900]

It's not just the piston speed, but also the side load on the major thrust face. It's why cylinders wear into ovals. You don't think this will occur at a higher rate when the oil is 150 degrees below its operating temp and you have a load sufficient to accelerate the car's weight? Vs. nearly zero load?

no I don't think it will occur at a higher rate.
It's basically been debunked a hundred times over that idling a modern car to warm up is worse for a multitude of reasons. The bogus myth was started from the days of carbs, as stated already, where the need was simply from the standpoint that fuel couldn't vaporize in a cold intake and the engine would run horribly or barely run, that's it. It was simply a necessity pre 1990.

Your example of piston lub at idle vs driving when cold is the opposite of how it is. Most of the lubrication in cylinders is from crank splash in a wet sump, which are pretty much all cars. Cold oil combined with ultra low rpm's means you are getting the bare minimum of lubrication. If there's any tangible difference it is that you will have MORE wear when idling an ice cold engine than simply driving it under load conservatively.

 

[Snicklefritz]

I mean, you gotta love all these oil threads. Should we start arguing about which brand is better already?

Whatever brand KIA uses, of course. That would MOBIL 5W30 synthetic.

 

[Volfy]

BTW, ever wonder why the engine starts up at high idle RPM initially, before dropping back down to a lower idle RPM?

ECU does this to boost oil pump speed so as to reach full oil circulation as quickly as possible. In fact, for most cars, the colder the ambient temp, the longer the engine will run at high-idle. The fact that the engineers felt that the lower idle RPM was insufficient for optimum startup oil circulation should tell you whether prolonged idling is a good idea for a cold engine.

 

[Snicklefritz]

Ironically, NO load doesn't necessarily guarantee NO wear. This is an easy misconception to theorize, by those without a solid understanding of tribology.

Having never even seen that word before, that would be me.

 

[rtv900]

BTW, ever wonder why the engine starts up at high idle RPM initially, before dropping back down to a lower idle RPM?

ECU does this to boost oil pump speed so as to reach full oil circulation as quickly as possible. In fact, for most cars, the colder the ambient temp, the longer the engine will run at high-idle. The fact that the engineers felt that the lower idle RPM was insufficient for optimum startup oil circulation should tell you whether prolonged idling is a good idea for a cold engine.

good point and exactly why fast idles were programmed in
Once they settle down it's time to drive, not putter for another 15 minutes.

 

[Snicklefritz]

BTW, ever wonder why the engine starts up at high idle RPM initially, before dropping back down to a lower idle RPM?

ECU does this to boost oil pump speed so as to reach full oil circulation as quickly as possible. In fact, for most cars, the colder the ambient temp, the longer the engine will run at high-idle. The fact that the engineers felt that the lower idle RPM was insufficient for optimum startup oil circulation should tell you whether prolonged idling is a good idea for a cold engine.

This is exactly how I do it, wait for the less than a minute high RPM idle to drop, then I roll - unless Ima warming up the car for my wife, then I idle for as long as it takes. That is how I explained to my wife to do it. All I said was, "Wait until you hear the engine noise come down, then you can back out." When she asked why, I said, "The engine is circulating cold oil throughout the engine, once that's done you can drive. But go gently until you see the temperature gauge up all the way." She has a heavy foot.

 

[D.J.]

Whatever brand KIA uses, of course. That would MOBIL 5W30 synthetic.

Doesn't Kia recommend Total QUARTZ?

 

[Volfy]

This is exactly how I do it, wait for the less than a minute high RPM idle to drop, then I roll - unless Ima warming up the car for my wife, then I idle for as long as it takes. That is how I explained to my wife to do it. All I said was, "Wait until you hear the engine noise come down, then you can back out." When she asked why, I said, "The engine is circulating cold oil throughout the engine, once that's done you can drive. But go gently until you see the temperature gauge up all the way." She has a heavy foot.

Down here in the warm South, fast idle is rarely more than 5-10secs. I never actually timed it, but the ECU usually beats me to it, while I click my seat belt and hang my phone on the magnetic holder.

 

[Volfy]

Okay... back to the original topic of this thread.

While I am not a fan of using an ultra-wide multi-viscosity oil like 0w-50, I do like a little more margin than using 5w-30. Because I live here in the warm South, Summer heat can be brutal. We run 5w-40 instead, which provides a bit better high-temp protection, in case oil temp does creep up a bit past normal operation temp. The only caveat is that oil changes should be a bit more frequent to account for wear of the added polymers. We do that anyway, so no big deal there.

I don't bother getting my used oil analyzed. I'm certain I'm always draining used oil that still has good serviceable life left. Meh. Oil is cheap, and I don't need to get every last mile out of my oil. Just goes in the recycling tank at my local Advance Auto... sooner than later.

 

[Snicklefritz]

Doesn't Kia recommend Total QUARTZ?

View attachment 84431

Doesn't that predate the move to synthetic, which was in January '22, iirc.

 

[turboAWD]

Doesn't that predate the move to synthetic, which was in January '22, iirc.

Did the Stinger ever NOT use full synthetic from the factory? I'm unaware..

 

[lil_lurking_stinger]

Doesn't that predate the move to synthetic, which was in January '22, iirc.

I thought the Stinger engine always required synthetic?

 

[D.J.]

I thought the Stinger engine always required synthetic?

My Stinger (2018). Came from the factory with an oil cap that said (0w30) Which only exists as synthetic...

So, I too though it was always synthetic, but never called out specifically in the manual (2018 manual).

Later, there was a "service campaign" to replace the oil cap with one that read, 5w30


This is the cap my car came with!

 

[Snicklefritz]

Did the Stinger ever NOT use full synthetic from the factory? I'm unaware..

I thought the Stinger engine always required synthetic?

Don't know the answer to that. All I know is that the service had this sign up advising something different, i.e., the signage wasn't there before. I asked how long they had been doing that and they said since January. It was 2022, now that I see the time stamp. Heh, memory.

 

[Volfy]

My Stinger (2018). Came from the factory with an oil cap that said (0w30) Which only exists as synthetic...

So, I too though it was always synthetic, but never called out specifically in the manual (2018 manual).

Later, there was a "service campaign" to replace the oil cap with one that read, 5w30
View attachment 84439

This is the cap my car came with!

View attachment 84442View attachment 84441

So they actually went through the trouble of issuing a TSB and swapped out customers' caps... I wonder what the back story was on that one.

My '23 2.5T says 0W-30 too, which I basically ignore. Where I live, ambient temp below 30F cold engine starts only happen a few times out of a year, so the low temp side is of little practical significance to me.