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Discussion Starter · #1 ·
Who's using synthetic, and who's using 5w-30 instead of 5w-20?

I don't like the idea of 5w-20, as the flow is no better at cold start(both are 5w) but under hot engine or climate conditions, 20w is too thin to adequately protect engine parts AND not volatilize, IMO.

Anybody?
 

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I'd stick with 5W20. Manufacturers recommend a certain weight oil for a reason. Todays engines are built with such tight clearances that 30W in this engine may not get to all the places it needs to be due to it being thicker than the 20W. Better safe than sorry if it ever came down to an engine warranty claim.
 

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As well, Kia has a TSB out regarding a 'cam/crank correlation error' DTC if the wrong oil viscosity is used. It can actually cause your CVVT to be slow to respond, and will cause the DTC and a failsafe lockout of the CVVT system. I have seen this code come up (the exact DTC escapes me, but I can look it up if it's important to someone) and something as simple as an oil change (to our semi-synthetic 5W-20) has cleared it up, every time.
 

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2021 Forte GT w/GT2, Currant Red, SXTH Element Intercooler Kit, Evilla Exhaust, Takeda S2 Intake
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Kia recommends 5w-20 and that's good enough for me 'cause they warrant the engine for 10 years 100,000 miles if I use the oil they recommend.

It helps too if you know that several other car manufacturers have been recommending 5w-20 since 2001 -- like Honda and Chrysler.

You can find a lot of negative discussions about 5w-20 on oil company sites...and, of course, they have a better oil you should use...imagine that...LoL!
 

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Discussion Starter · #5 ·
As well, Kia has a TSB out regarding a 'cam/crank correlation error' DTC if the wrong oil viscosity is used. It can actually cause your CVVT to be slow to respond, and will cause the DTC and a failsafe lockout of the CVVT system. I have seen this code come up (the exact DTC escapes me, but I can look it up if it's important to someone) and something as simple as an oil change (to our semi-synthetic 5W-20) has cleared it up, every time.
Interesting...I know about the TSB for the oil filter, but didn't know about one for oil viscosity. In the owners manual and Kia tech literature, they say 5w-20 is "preferred" but that 5w-30 and 10w-30 can be used based on your area's climate/temp range.

We all know what can happen when oil thins out due to shear or fuel dilution. Starting with a 5w-20 concerns me in that regard. And basically, the recent move by some mfgrs to 5w-20 is entirely motivated by fuel economy concerns. This is fact, not opinion.

I'm okay with 5w-20 in winter months, but what about when it's 100+ degrees out and you're stuck in traffic. An potential overheat condition exists and that's when thinner oil can become volatile and thin even more, or foam, which is bad news for an engine.

BTW, the Kia dealers I've contacted are using 5w-30 and even 10w-30 on the Kia's brought in for oil changes.

Can you provide the TSB? Because that would definitely convince me to use 5w-20.
 

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Discussion Starter · #6 ·
Kia recommends 5w-20 and that's good enough for me 'cause they warrant the engine for 10 years 100,000 miles if I use the oil they recommend.

It helps too if you know that several other car manufacturers have been recommending 5w-20 since 2001 -- like Honda and Chrysler.

You can find a lot of negative discussions about 5w-20 on oil company sites...and, of course, they have a better oil you should use...imagine that...LoL!
Well, the negatives of using a 5w-20 on oil sites aren't merely superficial. Engineers know that heavier oils lubricate better, especially at high temp/heavy load, and protect against volatility or breakdown much better.

I actually read somewhere that Hyundai engineers were NOT in agreement with the company recommending 5w-20, as their engine research and testing indicated more wear with the 5w-20. I'm sure the EPA and CAFE were a major force behind Hyundai/Kia recommending 5w-20...and Honda and Ford also.

This is what worries me. Is 5w-20 just as good for the engine, or is it entirely fuel economy motivated, and marginally adequate for proper engine lubrication?

We're talking about longevity of an engine, not that the warranty covers something...in theory.
 

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Discussion Starter · #7 ·
Kia recommends 5w-20 and that's good enough for me 'cause they warrant the engine for 10 years 100,000 miles if I use the oil they recommend.

It helps too if you know that several other car manufacturers have been recommending 5w-20 since 2001 -- like Honda and Chrysler.

You can find a lot of negative discussions about 5w-20 on oil company sites...and, of course, they have a better oil you should use...imagine that...LoL!
Some useful oil info:
 

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Actually, I'd be interested to see the TSB, as well. When I took the New Model Training for the Forte, our instructor there told us of the occurrence, and said he was going to issue something to the dealers. I just assumed it was done, and never followed up on it. I just spent 20 minutes searching through 5 years of TSBs, Tech Tips, Recalls and Service Actions and I can't find anything other than the announcement when they swapped to 5W-20 for the 2005 model year. At that time they have said that 5W-30 is acceptable if 5W-20 is unavailable.

The code is either a P0016 or P0017 and we've only seen them in the Lambda engines (3.3 and 3.8 V6) thus far and it's only been a few isolated instances.

As far as I am concerned, as long as your oil is clean, I don't much care what you put in it - as long as it's not 15W-40!
 

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5W/20 is recommended by some manufacturers due to a better Fuel Economy Rating. My owners manual recommends the 5W/20 for better fuel economy (thinner oils provide less resistance) and better cold weather performance. I live in Texas, rarely does our temperature get below 0 degree F. Due to our temperatures being warmer most of the year, I will be using Mobil 1 10W/30 in my engine........the viscosity recommendation shown in my owners manual.
 

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Discussion Starter · #11 ·
I'd stick with 5W20. Manufacturers recommend a certain weight oil for a reason. Todays engines are built with such tight clearances that 30W in this engine may not get to all the places it needs to be due to it being thicker than the 20W. Better safe than sorry if it ever came down to an engine warranty claim.
The whole "tight tolerances" of today's new engines is a myth. What, there weren't tight tolerances before? You know, piston rings, valve guides, valves seats, machined parts. So, they all had loose tolerances in the past? No hardly.

IMO, 5w-20 offers marginal lubrication and wear protection under high temp and high load conditions.

Ask yourself why 5w-20 isn't recommened anywhere but in the US market. Answer: It's being forced on US car owners in order to conserve fuel, nominally. It's not worth it. Not worth the inferior protection it provides your car engine.
 

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Discussion Starter · #12 ·
5W/20 is recommended by some manufacturers due to a better Fuel Economy Rating. My owners manual recommends the 5W/20 for better fuel economy (thinner oils provide less resistance) and better cold weather performance. I live in Texas, rarely does our temperature get below 0 degree F. Due to our temperatures being warmer most of the year, I will be using Mobil 1 10W/30 in my engine........the viscosity recommendation shown in my owners manual.
I agree. Right now I'm using 5w-30 but may go to 10w-30 permanently. Unless you're consistently close to 0 degrees F, you don't even need a 5w.

Building oil pressure quickly at cold start is more important then flow. Even 10w oil flows to -33 F. Oil pressure is the critical issue on cold start. 0w and 5w oils provide a low oil pressure scenario until the oil thickens. 10w and 15w build oil pressure much faster.
 

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I'm thinking of getting a commuter car for work(80 miles round trip) and the EX fuel economy package is what I'm interested in. If I get this car I will use a semi synth 5/20 in the winter and non synth 5/30 in the summer based on what I've read here. Motor Oil
FerrariChat.com - FAQ: Motor Oil Articles by Dr. Ali E. Haas (AEHaas)

I agree. Right now I'm using 5w-30 but may go to 10w-30 permanently. Unless you're consistently close to 0 degrees F, you don't even need a 5w.

Building oil pressure quickly at cold start is more important then flow. Even 10w oil flows to -33 F. Oil pressure is the critical issue on cold start. 0w and 5w oils provide a low oil pressure scenario until the oil thickens. 10w and 15w build oil pressure much faster.
 

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5W-30 would be a better choice than 10W-30. Cold start viscosity is the only thing increased with 10W versus 5W, and thicker oil at startup isn't desirable.
 

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Discussion Starter · #15 ·
5W-30 would be a better choice than 10W-30. Cold start viscosity is the only thing increased with 10W versus 5W, and thicker oil at startup isn't desirable.
However, thicker oil clings to engine parts better(between starts) and builds oil pressure quicker, both desirable at cold start up.

I'm going with 10w-30 from here on out. 10w-30 flows at -33F...5w-30 flows at -36F. Big deal, the difference is negligible. Also, 5w-30 needs more viscosity improvers, which means more shear.
 

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What temperature do you think the oil is when you switch the car off? 5W-30 is the same thickness at operating temperature as 10W-30. If you want more 'cling' you'll need to move up to 5W-40. And you're wrong about which builds pressure more quickly. Thinner oil, when cold, flows faster.
 

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Discussion Starter · #18 · (Edited)
What temperature do you think the oil is when you switch the car off? 5W-30 is the same thickness at operating temperature as 10W-30. If you want more 'cling' you'll need to move up to 5W-40. And you're wrong about which builds pressure more quickly. Thinner oil, when cold, flows faster.
How oil clings to engine parts after the engine is turned off and oil has drained back into the crankcase has very little to do with temperature. The point is that a thicker oil provides a thicker film on engine parts while operating AND while sitting...which helps on oil starved startup. 10w is thicker than 5w at cold temp. Ergo, it will cling to engine parts better between engine operation. This is a no-brainer.

You're wrong about a thinner oil building pressure more quickly. Oil flow and oil pressure are 2 different things. Please research this if you still don't agree.

Basically, you want an adequate film of oil to lubricate and protect engine parts. You also need something thicker than 20W at high operating temps.

5w-30 is a good choice, I use it all the time. But I am now switching to 10w-30 due partly to the warmer climate I live in and also for a more quiet engine during warmup, and less viscosity shear from a 10w-30 compared to a 5w-30.
 

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You're saying the oil is cold when you shut off the engine, which of course is incorrect. If is it cold, then 10W-30 will cling better than 5W-30. The fact that the oil is hot at shutdown means that both oils will drain at the same rate. Thicker oil does provide a thicker film on engine parts, but a 10W-30 and a 5W-30 will cling at the same rate because you're talking about OPERATING TEMPERATURE, not STARTUP TEMPATURE. 10W-40 flows slower than 5W-30 when cold. They flow (and cling) at the same rate when hot. If you are in the habit of starting your engine and shutting it right back off, yes...you'll have more cling from a thicker oil. But I sincerely hope you're not doing that. Once the oil has reached operating temperatures, they drain at the same rate if they are both Xw-30.

To say that cold oil and hot oil drains into the crankcase at the same rate is also false..otherwise your claim that cold oil clings better to engine parts has no merit.


Use what you like....just know that your theories are backward.
 

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Discussion Starter · #20 ·
You're saying the oil is cold when you shut off the engine, which of course is incorrect. If is it cold, then 10W-30 will cling better than 5W-30. The fact that the oil is hot at shutdown means that both oils will drain at the same rate. Thicker oil does provide a thicker film on engine parts, but a 10W-30 and a 5W-30 will cling at the same rate because you're talking about OPERATING TEMPERATURE, not STARTUP TEMPATURE. 10W-40 flows slower than 5W-30 when cold. They flow (and cling) at the same rate when hot. If you are in the habit of starting your engine and shutting it right back off, yes...you'll have more cling from a thicker oil. But I sincerely hope you're not doing that. Once the oil has reached operating temperatures, they drain at the same rate if they are both Xw-30.

To say that cold oil and hot oil drains into the crankcase at the same rate is also false..otherwise your claim that cold oil clings better to engine parts has no merit.


Use what you like....just know that your theories are backward.
I said no such thing. Both 30W's will cling to the engine parts the same after a hot shutdown, in theory. But you should be aware that a 5w-30 will have higher viscosity shear than a 10w-30, due to more polymer additives used to maintain a larger spread. In essence, it has less base oil/more additives. So, even hot, 10w-30 will likely be thicker than 5w-30 over time(once shear has occured) and will therefore cling better to engine parts. Also, for you to guess at what exact viscosity an oil may have reached on any shutdown is foolish.

10w-30 flows at -33. But, if you have such an adversion to using 10w-30 instead of 5w-30, than by all means, continue with that misconception. It makes no difference to me.
 
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