Can an Oil Change Make More Power? We Test Idemitsu Zero Eco Medalist and Find Out!

By Mike Kojima

Can you make significant power gains just by changing oil?  In the past, we have proven that switching from a lower grade mineral oil to a premium synthetic oil can be good for a couple or three hp. However, is it possible to make serious gains in power from just an oil change by changing the viscosity of the oil as well as the type? 

We set out to experiment and find out.  Our subject in this test was our Project EP3 Civic Si.  We are currently using this car as our company get around mobile and it sees duty as a commuter and parts runner.  Project Si is currently powered by a stock K20A3 engine and we figured it would make a perfect candidate to test low viscosity and low friction oils since it was designed to run them. 

Our super low friction oil is Idemitsu ZEPRO 0W-20. This blend of energy saving Idemitsu oil is fortified with Molybdenum which protects against wear. Idemitsu is factory fill on Honda's and many other Japanese base cars so if you have not heard of the brand, be assured that its good stuff.  

The formulation of ZEPRO 0W-20 was developed for cars using stop-start fuel-saving technology, the feature that shuts engines off at lights to save gas. Since most of a street car's engine wear occurs during starting when the engine is cranked and run for a small bit of time with zero to little oil pressure, engines with this feature need more film protection against wear. 

For our performance purposes, we figured that the moly that was intended to work well for continuous starting and stopping would provide extra protection against wear for driving hard! ZEPRO 0W-20 is a high quality synthetic oil that in addition to the moly, has special friction modifiers as well as traditional extreme pressure additives to deliver ultra-low viscous and mechanical friction.

Since the 0W-20 viscosity rating seems pretty damn thin, we chose to run it first in our K20A3 engine because it was designed by Honda for thin, low friction oils. The K20A3 has tight bearing clearances and enough oil pump capacity to tolerate the thin stuff no problem. 5W-20 is the factory fill on this engine. 

For our test, we went out and bought the cheapest decent mineral based oil we could find on sale at Autozone.  We selected the factory recommended viscosity which was this 5W-20 Valvoline. Decent stuff but nothing high tech or fancy. 

ZEPRO 0W-20 is just one of Idemitsu's super mileage ultra-low friction synthetic oils in the ZEPRO line. They offer a 0W-16 formulated for Hybrids, 0W-20 dexos-1 for GM turbo engines, dexos-1 5W-30 formulated especially for the GM Ecotec engine and ZEPRO 5W-40 formulated for high-performance Euro engines like Porsche and BMW that need a thicker oil.


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Wednesday, May 09, 2018 5:12 PM
Shame on you for this. Seriously.
Wednesday, May 09, 2018 5:23 PM
Royal Purple used to make the same claim some 15 years back, turns out they just used really thin oil for less resistance but engine protection suffered. Experienced this personally with highly accelerated wear and oil consumption.

now I'm not saying Idemitsu ZEPRO 0W-20 is the same, but short of running this for 80k on an engine and seeing the results (like my experience with royal purple) it can't really be proven otherwise... I'll take oil that provides protection at the expense of 8hp personally
Wednesday, May 09, 2018 5:28 PM
also, why didn't you test this against synthetic oil? nobody that cares about pulling the last 8hp out of their car is gonna be running dino oil anyway...
Wednesday, May 09, 2018 7:45 PM
Viscosity actually has nothing to do with how well an engine oil prevents engine wear. Film strength is what prevents engine wear and, in modern oils, there is no significant correlation between viscosity and film strength. A higher viscosity oil will not necessarily provide better protection in extreme conditions. A 0W-20 motor oil with excellent film strength will prevent wear much better than a 10W-40 motor oil with poor film strength.

Modern oils can produce incredibly high film strength at very low viscosities. As long as you can get adequate film strength then lower viscosity is always better from a performance standpoint. Lower viscosity means less drag, better cooling, and superior lubrication because more oil is flowing through the oil pump and into the engine rather than simply being bypassed back into the oil pan.

Thinner oil also drains back into the sump more quickly, reducing the risk of oil starvation. Thinner oil releases trapped air bubbles more quickly and is more resistant to being whipped into a foam by the churning assembly of parts in the crankcase. So long as there is adequate film strength, a thinner engine oil will always be superior to a thicker one.

Martin Gonzales
Martin Gonzaleslink
Wednesday, May 09, 2018 8:04 PM
@corn: Why would you make that statement? We have nothing to be ashamed of for reporting our real world findings. We have actual data to prove our point and we also mention the potential downfall for using a much thinner oil. Maybe I'm misunderstanding your statement, but at the moment I really don't see what you're getting at.
Martin Gonzales
Martin Gonzaleslink
Wednesday, May 09, 2018 8:12 PM
@warmmilk: All valid points and I for one agree with you (I'll take protection over HP most of the time). This will be a long term test and we plan to continue using this oil for at least a few more oil changes, so we'll see what we find.

As for folks that care about extracting HP not caring about using dino oil, I disagree...kinda. HP is efficiency, and efficiency will yield more MPG. So MPG freaks may not be horsepower freaks, but they definitely care about extracting horsepower to increase their MPGs. In the follow up article we will also report back with our MPG data before and after the 0/20 Idemitsu.
Dan DeRosia
Dan DeRosialink
Thursday, May 10, 2018 4:34 AM
Viscosity has a strong correlation to how well bearings with a fully developed fluid film keep performing as bearings - it's integral to the entire mechanism for how things like main and rod bearings work! Other stuff that's in the boundary lubrication regime like cam followers yeah, film strength comes into play.
Thursday, May 10, 2018 5:43 AM
As soon as I read the title I knew what the finds would be. I mean, in Gran Turismo you always gained a few ponies if doing the oil change.
Thursday, May 10, 2018 12:26 PM
Like I said, idk if this oil sucks for protection or not, just saying the last oil that came out with hp gain promises sucked for protection

@Martin Gonzales
A few oil changes isn't enough to see long term effects... I'd wanna see at least 30k...

synthetic oil is better than dino oil for MPG generally too... point is, enthusiasts use synthetic oils, people that go to the track use synthetic oils... the kinda people that would buy this Idemitsu ZEPRO oil use synthetic oil. so this should be compared to a synthetic oil and not " the cheapest decent mineral based oil we could find on sale at Autozone"
Thursday, May 10, 2018 5:41 PM
@Dan DeRosia

Say that to all the BMW M3's and M5's with spun bearings out there. The combination of high-viscosity 10W-60 oil that BMW specified and tight rod bearing/conrod side clearance was entirely to blame for those failures. Low-viscosity oil with high film-strength is now well-known to eliminate that issue.

Oil FLOW is lubrication. The argument for viscosity being critical in the operation of plain bearings would only hold up if oil wasn't constantly being pumped through the engine. Plain engine bearings are not designed to be lubricated by a stationary oil film, they are designed to be lubricated by a flow of oil.

Your argument about a "fully developed fluid film" is totally meaningless in the face of a dynamic engine environment with constantly flowing oil.

Higher viscosity just makes for higher oil pressure, and oil pressure is not what keeps the crank and crank bearings separated. They are kept separated by the non-compressible hydrodynamic liquid oil wedge that the oil pump is constantly renewing through fluid flow. ALL liquids are non-compressible, it does not matter what their viscosity is. Water cannot be compressed any more than pancake syrup.

As long as the engine is delivering adequate oil pressure to keep enough oil flowing to the critical components then any additional pressure is of no benefit. The ideal engine oil is only just thick enough to deliver enough oil pressure with a reasonable safety buffer. Anything thicker than that just creates needless additional pressure which causes oil to be bypassed back into the oil pan rather than pumped through the engine. That bypassed oil represents lost lubrication and cooling capacity, it is doing nothing to help the performance of the engine.

What matters most to engine durability is film strength, and film strength is largely determined by the additive package in an oil. It has nothing to do with viscosity.
Thursday, May 10, 2018 6:38 PM
It'll be easy for somebody else to go out and test another performing otc oil to compare this against if they're so inclined. I like the rest, the results seem honest.


To say viscosity has no effect on engine wear, longevity and lubrication film strength is to redefine their very definitions.

The list of evidence supported by peer reviewed literature is too vast to cite here. Two months (around there) ago in the stle magazine they described this itself.

Other sources easily found sport the opposite of what you're saying.

The focus on film strength divorcing it from viscosity kinda reads like that rat 540's stuff.

Way too many other factors to get tribologists to agree with such a broad statement.
Dan DeRosia
Dan DeRosialink
Friday, May 11, 2018 4:19 AM

You've been reading 540rat's blog. He's wrong too. Or, he's narrowly testing one regime of lubrication and assuming it applies to everything because his engine combination doesn't typically fail main bearings.

Viscosity is what draws the oil into the incompressible wedge in the first place, and what keeps it from squirting out the sides of the bearing shell. Why yes, oil is incompressible (ish - real oil tends to be aerated) but an automotive style journal bearing has two open sides - it doesn't need to compress, it can and does just flow out the sides!

Now, you do need supply flow because that's the only thing that's taking heat out of the system, but other than that there's not much correlation between the fluid film between the bearing and journal and load capacity. Automotive style bearings are only one way to make fluid film bearings work - if you do it right, you can design stuff to work (for a while until it gets too hot) without any flow.

So in the end just because the only effect you can easily measure with viscosity is oil pressure (which doesn't matter) doesn't mean that's the only effect viscosity has.

Source: My last day job was as a test engineer in the R&D lab of a fluid film bearing maker who did stuff ranging in size from turbocharger bearings to stuff for power plants. I read textbooks on how the stuff worked, picked the brains of the PhDs who were designing the analysis code to figure out how it all was working, and tested stuff to failure using test rigs larger than a semi truck and trailer.
Dan DeRosia
Dan DeRosialink
Friday, May 11, 2018 4:25 AM
See if you can find a copy of Booser's Bearing Design and Application - it's a textbook from 1957. The analysis methods can be made more detailed now due to computers vs working the math out by hand and there's new materials at play compared to then (for industrial scale stuff anyway) but the math and ways all of this work were figured out back then.
Friday, May 11, 2018 5:16 PM
@Dan DeRosia
I can't find that book, but I have this close by. ISBN 978-1118637241

Pretty good stuff.
Dan DeRosia
Dan DeRosialink
Saturday, May 12, 2018 10:20 AM
I would have figured that there'd be a newer edition - as you might have guessed I have the older one. ;)

I actually still find the fluid film bearing stuff interesting even though I moved on from there - there's a lot of stuff that's well past what people know about, and we were doing some genuinely interesting work with materials and designs.
Mike Kojima
Mike Kojimalink
Sunday, May 13, 2018 11:03 PM
Corn, why do you feel this way, we tested this oil on this motor and these were the results.
Tarik Laaraj
Tarik Laarajlink
Wednesday, May 16, 2018 6:55 AM
Mike can we have some data from Blackstone after 3k miles?

Cool stuff!
Wednesday, May 16, 2018 5:44 PM
mike. when this site started it was more signal less noise. Test parts and prove their worth. Now it is pimp any product that will give us free stuff and all testing is positive and everything is great. Project cars getting more costly and unrealistic to the core group you started by representing. but hey, free parts right ?
Monday, May 21, 2018 10:06 AM
Well I agree and disagree about the oil "snake oil" aspect of this. But I will say I'm really looking forward to the long term affects. I for one work in an industry that lubricants make or break a machine. I work in industrial maintenance. Plastics right now. We have a few machines with over 3 million cycles on them. They have proprietary grease and oils. But the wear is negligible. Other machines have barely broken 700,000 cycles. But had shitty mp2 or hp2 grease. And they are hammered.
I like this project because it is cheap. That being said. Mike could you weild your industry wide magic wand, and make K&W or someone make quality coilovers (or even koni inserts) for the Acura ILX.
I know the car is a joke new. But used it's a pretty good bargain.
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