5w30 vs 5w40 for Honda K24 2.4l 320hp fully built motor that will be used for daily drives.

Flyingdutchman

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I was thinking the same, i am owing a Honda S2000 with the F20C engine. 9.000 RPM, high piston speed.
For this engine Honda reccomends also 10w-30 or 5w-40. The later one surprisingly for winter, below freezing point. (??)
There are reports that the S2000 engine has a higher then average Oil temperature. I dont know it.

It is correct in my opinion that you try to select a oil based on the bearing clearances. If you use -30 oil look for a oil with a HTHS over 3.5 for this high reving engines. I decided to try a thin -40 oil as best compromise and ended up using Shell Helix Ultra 5w-40. This oil is based on GTL and has a viscositiy of 12.9, it is on the borderline to a -30 Oil. It carrys a lot of good approvals.
So far, the engine runs great. It has oil consumption, i maybe try a different oil, but so far i am satisfied with it.
Do short OCIs and change the oil often because of the high piston speed and maybe high oil temperatrues.

Because of the high piston speeds and RPMs i am a little bit hesitant about the use of 0w-40 in these engines. 🤔 I am concernd that this oils shear quickly.

BTW, in the german S2000 Forum some "Experts" try to convince people to use 5w-50 oil. This year where 2 damaged engines reported, both engines sufferd rod bearing failure after hard use on the autobahn. Both engiens where filled with 5w-50 oil
Yes i was also wondering if there is a possibilty to mount an oil temp sensor which can communicate with the ecu and a gauge but there is no real good location for it.

I was always told that high rpm engines need thin oil to cope with the high rotational forces and prevent cavitation/starvation and better cooling.

I even heard stories that the 20k rpm motogp and old f1 uses 8w oil.

I am assuming that this is what happend with the s2000s on the german forum just like the stories with the bmw m v8 and v10 on 10w60.

It always nice to see that people on a forum know it better than Honda as one of the worlds largest car and motorcycle manufacturer with numerous decades of formule 1, indycar, motogp and world super bike experience/championships :ROFLMAO:

We are also currently running the same shell helix 5w40 gtl oil as you do so we will probably stick with it, nice to hear that you have good results with it in a similiar engine. Oil consumption is normal just by design of the Honda engines.

Funny is that the shell helix ultra 5w40 is also ferrari oem recomended for their n/a v8 and v12s. Which in terms of performance are pretty similiar.

I am aware of ato24, i buy Ravenol from them.
 
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412
Location
Munich, Germany
If you read this:


Honda (of course) nailed it weith their -30 and -40 reccomendation.


Problem about some "Experts" in German forums is, that they have a high account of postings (=Trustworthy!) and some claim to be and work as engineer with a lot of expirence about Oil.... :confused::rolleyes: One of the engineers wrote that a Oil pressure that is to high at idle is a bad thing. Why? Because somewhere in the engine a oil chanel must be clogged....

Enough bashing, i hope that this make some readers smile. And it explains why i am lurking around here and bug you with my bad english.
Back to topic.
 
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412
Location
Munich, Germany
"Reducing the oil clearance between the rod and main bearings and the crankshaft has a number of advantages. A smaller gap spreads the load over a wider area of the bearing surface and distributes pressure more uniformly across the bearing. That’s good, provided the bearing is strong enough to handle it. A smaller gap also decreases the volume of oil that has to flow into the bearing to maintain the oil film between the bearing and shaft.


That’s also good, provided the oil is thin enough (low viscosity) to flow well into the bearing. This also reduces the amount of oil pressure the engine needs, so some extra horsepower is gained by reducing the load on the oil pump."

 
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412
Location
Munich, Germany
If you like to try something new, ROWE makes extremly good oils.
Their full Synthetic 5w-40 has produced a row of stellar, perfect used oil analysises.


The viscosity at 100°C is 14.7, just a litte bit on the thick side for my personal taste in this application....
 

Flyingdutchman

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182
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The Netherlands
Honda (of course) nailed it weith their -30 and -40 reccomendation.
Yes i am a firm believer in honda, the second article you send also spoke about improper machining of cranckshafts and cylinders etc... especially by independent shops.

That also why i opted not to grind the cranck or bore or hone the cylinders.

This donor engine had 180.000 km and the measurements where like new.

Honda is known for having one of the best machining and tolerances hence why stock engines can spin up to 10.000 rpm.

The second article also explained why race engines sometimes have a slightley larger bearing tolerances, this due to the deformation of the rod.
I never new this.


That’s also good, provided the oil is thin enough (low viscosity) to flow well into the bearing. This also reduces the amount of oil pressure the engine needs, so some extra horsepower is gained by reducing the load on the oil pump."
Also this, but i also heard that because the thinner oil spends less time in the "hot" bearing it cools the bearings better and the oil does not degrade as fast due to the lower temperatures.
 
Messages
412
Location
Munich, Germany
The only "bad" thing that i am sure is, that the Honda S2000 engine is not Autobahn safe.
But nobody that knows a litle bit about engines and is in his right mind can demand that this engine can stand 10 Minutes of full throttle above 8.000 RPM. Nevertheless, people here in Germany try it agian and again...
Otherwise, i know that Honda engines are bulletproof.
 
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23,675
Location
Dallas,Tx USA
I was thinking the same, i am owing a Honda S2000 with the F20C engine. 9.000 RPM, high piston speed.
For this engine Honda reccomends also 10w-30 or 5w-40. The later one surprisingly for winter, below freezing point. (??)
There are reports that the S2000 engine has a higher then average Oil temperature. I dont know it.

It is correct in my opinion that you try to select a oil based on the bearing clearances. If you use -30 oil look for a oil with a HTHS over 3.5 for this high reving engines. I decided to try a thin -40 oil as best compromise and ended up using Shell Helix Ultra 5w-40. This oil is based on GTL and has a viscositiy of 12.9, it is on the borderline to a -30 Oil. It carrys a lot of good approvals.
So far, the engine runs great. It has oil consumption, i maybe try a different oil, but so far i am satisfied with it.
Do short OCIs and change the oil often because of the high piston speed and maybe high oil temperatrues.

Because of the high piston speeds and RPMs i am a little bit hesitant about the use of 0w-40 in these engines. 🤔 I am concernd that this oils shear quickly.

BTW, in the german S2000 Forum some "Experts" try to convince people to use 5w-50 oil. This year where 2 damaged engines reported, both engines sufferd rod bearing failure after hard use on the autobahn. Both engiens where filled with 5w-50 oil.
Yeah I couldn't imagine running a W50 in a 4 cylinder engine.
 

Flyingdutchman

Thread starter
Messages
182
Location
The Netherlands
The only "bad" thing that i am sure is, that the Honda S2000 engine is not Autobahn safe.
But nobody that knows a litle bit about engines and is in his right mind can demand that this engine can stand 10 Minutes of full throttle above 8.000 RPM. Nevertheless, people here in Germany try it agian and again...
Otherwise, i know that Honda engines are bulletproof.
Yes i am also wondering which part is known to fail with such use.

I know the japanese market s2000 engines use high octane fuel because in japan they have better fuel.
But even then the knock sensors should avoid that and i dont think knock would occour at such high rpms.

With 240 kilometers per hour /150 mph engine cooling is also maximum.

With 8000 a 9000 rpm the waterpump also displaces the most water for cooling.
Also the oil pump has the most presure at this rpm.

At WOT (wide open throttle) the ECU switches to a 12.5 lambda instead of regular 14.7. This richer mixuture should also cool a little.

I do agree that these engines where not really made for this usage.

My bmw e91n52 2.5 inline 6 also sees a lot of fast driving for longer periods but 180kmh /120mph on cruise control is only like 60 percent load for the engine instead 100 percent load on topspeed.
 
Messages
412
Location
Munich, Germany
Yes, but in my opinion the piston Speed is to high for long high speed runs. That creates to much stress to the rod bearings. And its mostly the rod bearings that fail from what i read. When i drive my S2000 on the autobahn, i play it safe and keep the engine around 6.000 RPM. That´s still 180 km/h - 112 MPH. 7.000 RPM are 210 Km/h - 130MPH. That is fast enough with a safe piston speed.

Of course i sometimes "Hit it", but only short burst. The Piston speed of these engines is just to high, especially above 7.000 RPM. This is my opinon. I am maybe wrong.

I am only using 98 octane fuel. I often use even 100 or 102 octan fuel. ROZ octane.
 

Flyingdutchman

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Messages
182
Location
The Netherlands
Yes, but in my opinion the piston Speed is to high for long high speed runs. That creates to much stress to the rod bearings. And its mostly the rod bearings that fail from what i read. When i drive my S2000 on the autobahn, i play it safe and keep the engine around 6.000 RPM. That´s still 180 km/h - 112 MPH. 7.000 RPM are 210 Km/h - 130MPH. That is fast enough with a safe piston speed.

Of course i sometimes "Hit it", but only short burst. The Piston speed of these engines is just to high, especially above 7.000 RPM. This is my opinon. I am maybe wrong.

I am only using 98 octane fuel. I often use even 100 or 102 octan fuel. ROZ octane.
Yes the f20c engines with 87mm stroke have a piston speed of almost 26m/s at 8900 rpm.

25m/s is normaly considerd the max. Even the current 290 hp 1000cc v4 honda motogp engines are around 25.5m/s if i am not mistaking.

The k24 we are building has an 99mm stroke which is considered very long compared to the square 87mm.

At 8000 rpm the piston speed is 26.4 m/s.

I agree with you that this is really in race engine or beyond race engine terrotory and not meant for long highspeed runs.

Dragsters can do 30m/s, but these are alluminium rods and replaced after every run which is only a couple of seconds.
 

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1,885
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Caldwell Idaho
Engine builders might be familiar with the Honda K series, a high output high revving 4 cyl engine built between 2000 and in some form still built today.

The engine:
In europe we got the civic type r, it uses an k20 (means 2 liter) block with a special better flowing head which has V-tec and VVT on the inlet camshaft.
The engine we are building uses the k24 (2.4l) shortblock from an EDM accord type S and is fitted with the K20 Type R head.

The internals consist of race cams with heavy springs, carrillo rods and 12.5.1 c

Thinner VS thicker:
The newest turbo Type r uses the k20c1 engine which produces 320hp out of a 2l turbo, it is advised to use 0w20.
The ferrari 458 which has a high revving n/a v8 is advised to use 5w40.
The older bmw M high revving v8 and v10 engines where advised to use 10w60 and had even thighter clearances, these engines where known for rod bearing failures.
I heard that modern motogp and formule 1 engines run on something like a single grade W8 oil, however those engines start already hot.

5w40 Thick oil:
- Beter extreme load bearing for better protecion under extreme conditions
- Is advised to use in the Type R and is used a lot with good results.
- Maybe a little better for the forged wisecos because the fit so lose during the cold start up.

5w30 Thin oil:
- Flows faster through the engine so is not exposed as long to the hot areas/bearings as the thicker oil, this cools beter and deteriotes the oil slower.
- Wont cavitate as quick as 5w40 does, the k20 has an extremely good flowing oil pump but cavitating of oil means that even for a short period the rod will probably seize and break. The engine will run 8300 rpm so that spins/flows pretty fast.
- Lighter engine running, maybe slightly more horespower but this is not our goal.
- Alot of k24s world wide run on 5w20 without any real problems as far as i know, also the specs from the factory where designed to use this oil.


So what do you guys think? I am not looking for brands or anything, only what viscousity you would advise and why/why not?
I would say the thick and thin oil "facts" above are pretty much nonsense.
 
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1,885
Location
Caldwell Idaho
You need the proper viscosity of oil to keep the parts seperated at operating temps as well as the load that is put on the engine. The w part is what allows quicker oil circulation at very low starting temps. The 30 or 40 numbers is the neasured viscostiy at a given high temps. . What oil viscosity does your engine need as startup temps? 5W allows starting well below freezing . What are the oil temps of your engine at operting temps and on the race you are tracking it? .
 
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Flyingdutchman

Thread starter
Messages
182
Location
The Netherlands
You need the proper viscosity of oil to keep the parts seperated at operating temps as well as the load that is put on the engine. The w part is what allows quicker oil circulation at very low starting temps. The 30 or 40 numbers is the neasured viscostiy at a given high temps. . What oil viscosity does your engine need as startup temps? 5W allows starting well below freezing . What are the oil temps of your engine at operting temps and on the race you are tracking it? .
Yes i know, i should have added that i meant with the thinner vs thicker was meant at operating temps.
 
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Jupiter, Florida
Consider that successful race engines employing ultra thin oils always manage oil temperatures extremely well. Thereby maintaining adequate viscosity, flow rates and internal cooling.
 
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