If 5w-20 is so good, why do HP variants use 5w-30?

[Auto-Union]

I'm generally up to speed on 5w-20. (pun intended) However, I have a Acura TSX loaner with the HP 2.4l (205 hp) and the cap calls for 5w-30. My Accord with the same build 2.4, (170hp) just (possibly) more compression or exhaust v-tech or boosted FI/SI mapping wears great on 5w-20. Now, if 5w-20 is the bee's knees, why can't it cut it in an engine with a few more HP and similar tolerances, bearing metallurgy etc. Is the safe working visc HT/HS threshold so close that a few HP could make the difference...and do you think mfgs are dialing-in LESS power to allow 5w-20 and fuel benefits?

Another thing is that we won't be seeing a back-spec to 5w-20 either, as their testing has apparently concluded. I think 5w-20 is perfect, where speced, but I do find it interesting that a bit more specific output pushed it over the edge. This should tell people who chip and tune their cars to "mod" their oil too. Funny too, the torque values on some of these 5w-20/30 engine variants is similar or identical, like my RSX vs RSX-S.

 

[buster]

AU, I've often wondered the same thing. Our engines are identical to the TSX, minus the power. I think it depends on the engine design. Some engines, like the Dodge Hemi, can handle a 5w-20 and are pushing over 300 hp. I'm inclined to believe it has to do with fuel dilution and shear stability. Lot of Honda vtec engines tend to shear oils and have realitively high fuel dilution. I think Honda recommends the 30wt for a cushion, in case the oil shears down to a low 20wt or even 10wt (never seen that happen). I think something like Redline 5w-20 would probably be the safest option if one wanted to run a 20wt in the engines spec'd for a 30wt.

 

[ThirdeYe]

To be honest with you, I don't know either. My car hasn't been back-specced to 5W-20 but Havoline DS (basically a 20-weight) came back with great wear and performed great. -shrugs- Maybe one of these days I'll actually try a true 20-weight

 

[Curious Kid]

Like I think you were hinting, if having the "same" engine working to produce the added HP, then I think the added thermal loads that come along with it is warranting the increase in running viscosity if for no other reason than margin of safety. Not that there's any truth to it, but to a degree that is a cost and weight cutting measure that might be in place of installing/upgrading aux. oil cooling devises. The bumping of visc. for such efforts would only hndle momentary spikes in output for otherwise lengthy levels would increase the running average that would likely otherwise overload a stock thermal management measures.

Just a through mind you.

Take care.

 

[Curious Kid]

Fuel dilution and shear potential are also good points Buster. So many variables!

Being that I'm not familiar with these engines/vehicles, I wonder just how much they really are alike - think bore/stroke, compressions, bearing area, valve travel and guide material, valve actuation mechanism(s), spring loads, max rpm, power curve, oil pressure curve and regulation pressures, oil filter, thermostat regulation temp., vehicle rolling resistance and drag (effecting power losses that are otherwise looked at as base loading for engine/tranny while sustaining level of operation on level ground), drive line losses, etc. I don't think I ever thought this out like this before - interesting.

Take care.

 

[Auto-Union]

Even though it is one of the best arguements, I don't hink Honda deals in "safety margins" or a "cushions". Either it works or it doesn't. For me, 5w-20 come in to use only in cooler temps.

Does anyone know if my 1998 CRV 2.0 was back-speced? I don't want to buy synth oil for winter for it.

 

[ThirdeYe]

No it hasn't been, it's a variant of the B-series motor I have, which also still requires 5w30 (which I think is silly) like I said, I used Havoline DS which is as close to a 5w20 as you can get with a 5w30 and it came back great. Up for using your CR-V as an educated experiment?

I personally think 5w20 would still be great in it.

 

[Auto-Union]

Just to re-focus my point, I'm questioning why the 5w-20 *oil* does not cut it, even though there are clear design differences between variants. Specific output alone should not dictate the thicker oil. Also, to re-state, is thwe threshold of acceptable visc performance so close, a few more HP would kill the engine w/5w-20?

 

[badtlc]

Quote:

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Just to re-focus my point, I'm questioning why the 5w-20 *oil* does not cut it, even though there are clear design differences between variants. Specific output alone should not dictate the thicker oil. Also, to re-state, is thwe threshold of acceptable visc performance so close, a few more HP would kill the engine w/5w-20?

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If 5w20 can handle a Ferrari, do you really think the honda engine is that much worse?

 

[SargeGTO]

Well....2004 GTO with a stock LS1 350HP calls for 5-30.
Blew that thing up and dropped in a LQ9 iron block 408 Stroker motor. Much higher compression/valve lift etc. etc.
guess what...takes 10-30

Difference in RWHP is double with the Stroker motor...same oil....

 

[Punkey71]

Quote:

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Some engines, like the Dodge Hemi, can handle a 5w-20 and are pushing over 300 hp. I'm inclined to believe it has to do with fuel dilution and shear stability.

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Buster,

I have the Hemi in question...the 5.7. the 6.1 Hemi doesn't use 5-20. I think it uses 5-40...I may be mistaken....but I know it doesn't use 5-20. As it's been explained to me, 5-20 is required so the MDS works correctly in the 5.7's. The 6.1's are not equiped with MDS. I've not heard definitive answers as to why the MDS requires it...not that I doubt it, I just haven't heard a solid answer.

Anyone have any insight?

p.s. Yep...over 300HP...I dynoed 320 RWHP a few months back...I've done a couple modifications...but nothing drastic.

 

[bar1]

Quote:

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If 5w20 can handle a Ferrari, do you really think the honda engine is that much worse?

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The doctor says hi isn't pushing his cars. If that Ferrari was driven like it was meant (at a track, WOT out of every turn), you would want factory spec. oil in it.

 

[jmb106]

Quote:

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Even though it is one of the best arguements, I don't hink Honda deals in "safety margins" or a "cushions". Either it works or it doesn't. For me, 5w-20 come in to use only in cooler temps.

Does anyone know if my 1998 CRV 2.0 was back-speced? I don't want to buy synth oil for winter for it.

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Just some food for thuoght, I am currently on my 1st OCI of 5w20 in my 99 honda civic W/ the 1.6 non vtec motor which is speced for 5w30. Couldn't be happier w/ it it's like a different motor runs smoother, revs free'r, and gets a little better MPG. I don't think your 98 crv w/ 2.0 is that far from my civics engine arn't they built on the same platform? Hey buy a cheap dino 5w20 & give it a try if you don't like it dump it in a week or two.

joe

 

[jmb106]

Quote:

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No it hasn't been, it's a variant of the B-series motor I have, which also still requires 5w30 (which I think is silly) like I said, I used Havoline DS which is as close to a 5w20 as you can get with a 5w30 and it came back great. Up for using your CR-V as an educated experiment?

I personally think 5w20 would still be great in it.

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ThirdeYe,
I am already up for the experament,currently running 5w20 in my 99 civic lx & couldn't be happier.
joe

 

[Travis99LS1]

Quote:

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Well....2004 GTO with a stock LS1 350HP calls for 5-30.
Blew that thing up and dropped in a LQ9 iron block 408 Stroker motor. Much higher compression/valve lift etc. etc.
guess what...takes 10-30

Difference in RWHP is double with the Stroker motor...same oil....

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Hey sarge..just out of curiosity, why did you choose 10/30 over 5/30 in the stroker motor?

 

[SargeGTO]

Well...Dyson and I worked on this....the 10-30 is more shear resitant under a load....than a 5-30...something about fewer VI's....

 

[widman]

Great discussion. Now WHY can't I convince the local Honda dealer to stop using 15W-40 and 20W-50?

 

[kr_bitog]

Here is the info I got from the Japanese literature and my own test with Toyota 1NZ-FE.
When Toyota start adopts the use of 5w-20/0w-20 on their engine, they have modified the piston ring tension and the piston clearance to the cylinder. The other thing is they modified their valve timing controller mapping as well. I guess why they only spell the TSB recently because they need to have evidence to ensure this does not cause major issue on the fields.

I believe with certain w-20 oil may not cause issue, but with some it may cause the noise or compression issue.

So in the case of the acura, it is recommended 5w-30 because the engine might be designed with bigger piston clearance to handle the extra expansion from heat, so when people do not drive hard enough the clearance is too big that may cause higher oil consumption.

However this is only my thinking..but don't flame me

 

[Pablo]

Quote:

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Here is the info I got from the Japanese literature and my own test with Toyota 1NZ-FE.
When Toyota start adopts the use of 5w-20/0w-20 on their engine, they have modified the piston ring tension and the piston clearance to the cylinder. The other thing is they modified their valve timing controller mapping as well. I guess why they only spell the TSB recently because they need to have evidence to ensure this does not cause major issue on the fields.

I believe with certain w-20 oil may not cause issue, but with some it may cause the noise or compression issue.

So in the case of the acura, it is recommended 5w-30 because the engine might be designed with bigger piston clearance to handle the extra expansion from heat, so when people do not drive hard enough the clearance is too big that may cause higher oil consumption.

However this is only my thinking..but don't flame me

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Grasshopper - your thinking is quite clear.

 

[Titan]

TEMPERATURE! A higher performance engine is expected to endure much more aggressive driving, which raises oil temperature...which decreases viscosity. So, the end result is that at the normal upper end of expected oil temperatures, the engineers want a viscosity of XX.XcSt, therefore, different viscosities are spec'd. That's why some choose to run sports cars with a 10 weight when puttering around town up to a 60 weight when at WOT on a track, the viscosities at the respective resultant oil temperature are similar.