Are engines really engineered to use 5W-20?

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Somebody on another forum is trying to convince me that my engine might have oil starvation issues because I'm running 5W-30 in it, even though it says 5W-20 on the filler cap, since "the passages are smaller and the clearances are tighter". Specifically, it's a Honda K24Z1. I find that hard to believe, but I don't know if this was an engine that previously called for 5W-30.
 
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On that engine you will have no problems with 5w-30. Not only is that oil specd on the K series engines in the TSX and SI, it is listed as an acceptable alternative in your users manual and a recommended oil in other regions. Ford and Honda began the push for 20 weight oils in the '90's. The K series debuted in 2001. So I'm sure it was "designed to run on 20 weight oils" but wasn't designed to run on only 20 weight oils, and obviously runs very well on 30 weight oils. For a company to use 20 weight oils during their epa/cafe fuel mileage testing, 20 weight must be the only oil recommended to consumers, which is why they don't recommend it in the US. On the other hand, I happily run 5w-20, and have to ask... why don't you?
 

Dave Sherman

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Thanks, I didn't think there would be issues with 5W-30. I will say the engine is quieter and makes less clatter when cold with 5W-30 (Castrol GTX, had Syntec 5W-20 before). I can't tell any noticeable drop in gas mileage since the change. So for me, I'd say I get a small benefit using 5W-30 over 5W-20, and no detectable benefit going the other way.
 
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 Originally Posted By: bepperb
On the other hand, I happily run 5w-20, and have to ask... why don't you?
I don't know about Dave, but I find 5W-30 to be much more readily available, especially with Dino oils. I buy XW-20 weight on sale **if** I can find it but often I end up with 30 weight. eg, Mobil 1 AFE: I had the $10 rebate from Mobil, but WallyWorld only sees fit to stock the 0W-30. Believe me I looked high & low for the 0W-20. I keep meticulous records of Fuel Economy and darned if I can discern a FE consequence...
 
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My Fit does not tell me I can run other grades. It just makes a statement that 5W20 provides year-round protection. That made me nervous. I think my CR-V manual has a bit of an escape clause, saying 30 weight is okay if nothing else is available. That being said, I know there are plenty of Fit owners running 30 weight and have even seen a good UOA or two. But back to the k24, mine in my CR-V has had 30 weight most of its 7 year life. I wasn't afraid of 20 weight, it just wasn't widely available in my area when I first got the car. Then, after getting on bitog and finding sales and closeouts wheren 30 weights were typically prevalent, I went back to 30 weight again. Not a hiccup from the engine. There's 10W30 in it right now. Most of these oil starvation people are "honda people" and not "oil people." bepperb is right, there's no reason NOT to run 20 weight. But as far as causing damage....negative ghostrider.
 
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 Originally Posted By: Dave Sherman
Somebody on another forum is trying to convince me that my engine might have oil starvation issues because I'm running 5W-30 in it, even though it says 5W-20 on the filler cap, since "the passages are smaller and the clearances are tighter".
Clearances are the same as they`ve always been. CAFE.
 

Kestas

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Dave, what proof does this guy have on the geometry of clearances and passages? I once did an informal survey of specified bearing clearances over the decades and I didn't see much correlation with bearing clearance and specified oil viscosity. Also, many companies are now making the new viscosities backward-compatible with older vehicles that originally specified thicker oil.
 
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From my understanding, it's physically impossible for an engine only to be able to run on one viscosity grade of oil. Whatever is specced, you can almost always go one grade without blowing anything up. That said, you always want to use the thinnest oil that'll work for you. Thin oil generates less drag, and it cools better because it transfers heat better. Yes, CAFE, maybe it's all a scam, blah blah. File that under "H" for "healthy skepticism". Whether or not the engine was specifically optimized for 5w-20, it will run all day and last a VERY long time on that viscosity. If it couldn't, the owner's manual would list something else.
 
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 Originally Posted By: d00df00d
From my understanding, it's physically impossible for an engine only to be able to run on one viscosity grade of oil. Whatever is specced, you can almost always go one grade without blowing anything up. That said, you always want to use the thinnest oil that'll work for you. Thin oil generates less drag, and it cools better because it transfers heat better. Yes, CAFE, maybe it's all a scam, blah blah. File that under "H" for "healthy skepticism". Whether or not the engine was specifically optimized for 5w-20, it will run all day and last a VERY long time on that viscosity. If it couldn't, the owner's manual would list something else.
you always want to use the thinnest oil that'll work for you. I have learned the exact same thing over the years as well.
 
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I know many here at BITOG use 20wt. oils with success, but what about the really long haul? I have used 30wt. oils for many years and have proven to myself that they will protect engines for extremely high mileage. I'm not critizing 20wt.but not ready to switch over.
 
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 Originally Posted By: tig1
I know many here at BITOG use 20wt. oils with success, but what about the really long haul? I have used 30wt. oils for many years and have proven to myself that they will protect engines for extremely high mileage. I'm not critizing 20wt.but not ready to switch over.
Well,I would have to say;if its working for you,go with it.
 
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The timing chain tensioners on the Ford 5.4 Triton 3 valve motors are adjusted & activated by oil pressure provided by the 5W-20 viscocity along with proper function of the VTC's!!!
 
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I agree but I think a lot of people over anaylize that fact. I'm 1500 miles into a run of M1 0W40 in my 08 4.6 3V and have noticed NO differences at all in mileage, power, or engine noise. Frankly I'm a little amazed because I was at least expecting it to be a little doggier or something! Who knows...there probably is way more leeway on viscosity on these new engines than we think. Just my .02
 
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 Originally Posted By: RISUPERCREWMAN
The timing chain tensioners on the Ford 5.4 Triton 3 valve motors are adjusted & activated by oil pressure provided by the 5W-20 viscocity along with proper function of the VTC's!!!
If they can't handle the difference in viscosity betweeen a 20 and a 30 then they can't handle a 15F change in oil temperature. What a lousy engine (assuming you are correct).
 
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Variable valve timing and tensioners that rely on oil pressure don't like thick oil. This is only a problem when cold. When hot, thicker oils are well within their flow needs.
 
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The wife's '08 mustang gt loves the Rotella syn 5w40, for some time now. Look up the bearing clearnaces for your engine as far back as you can go, and compare it to today's. I believe you will not find much difference. The difference is first and foremost, CAFE , and second the advancement oil has made in the last 10 years. You could not pull that off 10 years ago, but oils have come a LONG way since then, with most dino Grp II and III oils , providing as good or better than most synthetics of a decade ago.
 
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It all boils down to the oil temp. If engine is designed to keep the oil temp under 100C, even low viscosity oil can prevent low wear (HTHS 2.6 is sufficient). As multiple SAE papers show, wear goes up with oil temps going up and HTHS 3.0 may be requited at 130C. Engines capable of heating oil to 150C (under high load of course) will require even higher HTHS such as 3.5 (ACEA A3) or 4.0 (HDEO). When Toyota switched to 5W20 oil in Corolla with the same engine, they simply replaced the dipstick with new markings to keep the oil higher and thus decrease oil temp. Also Toyota installed engine oil coolers on newer cars with towing package. This explains the higher viscosities recommended overseas: high speed driving on German autobahn heats the oil a lot and xW20 oil with HTHS of 2.6 is not enough to prevent a significant wear. This is not an issue in US as we have speed limits and most people drive the 10 miles commute barely keeping the oil warm.
 
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