🔴💊 Engine Oil Red Pill Thread: Only Post If You Have UOA - Official Honda Civic Type R K20C1 Engine Oil Analysis

[iforgettopee]

it's really impressive the 0w20 isn't sheering thin due to high temps from the track driving you're doing. it's one of the main reasons I feel obligated to change my oil before every track day for peace of mind.

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[johnloov]

it's really impressive the 0w20 isn't sheering thin due to high temps from the track driving you're doing. it's one of the main reasons I feel obligated to change my oil before every track day for peace of mind.

The oil held up very well.

Observations

• All oils shear with use; the rate accelerates sharply with temperature. That’s the key lesson—once bulk oil temp climbs, viscosity loss can snowball.
• On a stock-cooled engine, switching from 0W-20 to 5W-30 consistently raised water and oil temps by ~15–20 °F on the same track, pushing peak oil to ~241 °F (as Zygrene saw on a hot day in his modified Integra Type S).
• Modern engines have tighter clearances and high flow demands. A thicker oil increases pump work and can reduce flow, which tends to push temps higher unless cooling is upgraded.
• Example: Eric’s Type R with dual oil coolers runs Motul Power 8100 API SP 5W-30 oil for ~5,000 miles including multiple track days while holding water temps ~220 °F. Super Excellent Blackstone results.
• A single auxiliary cooler mounted in front of the radiator can impair radiator airflow; net cooling may be negligible or negative. Proper dual coolers with ducting are far more effective.

Takeaways

• Keep oil temperature in check to control shear.
• Stock engine/stock cooling: 0W-20 is the safer choice for track, maybe 5w-30 can be okay if they daily the car and want to extend oil changes to 5-10k miles intervals for some reason. But.. All oils get contaminated after ~2000 miles and start to degrade. Also the expert at Motul also recommended I go with 0W-20 on a stock engine after almost a 1 hour call. He also validated thicker will increase oil temps. All experts, dyno results, and tests all prove this now.
• Modified with dual oil coolers: 5W-30 is viable, proven it works, oil last long, doesn't sheer much.
• I’ve also seen dual-intercooler setups running 0W-20; I’ll work on capturing comparable data for that configuration.
• More flow → better cooling. Convective correlations for internal flow show h ∝ Re^m (e.g., Dittus–Boelter), so higher mass flow increases the oil-side heat-transfer coefficient in the cooler.

I asked Zygrene to try 0W-20 and see if it helps. He’s currently on Pennzoil Ultra Platinum 5W-30 and noticed higher temps after switching. I also had WOT Jason ( also runs PUP 5w-30 with dual oil coolers ) review my logs; he confirmed the car is running cool on the current stock setup, even under hard driving. These are validated data points from people with more experience than me.


He hit over 241F that day.

It would be great to see if anyone has any experience overheating their stock FL5 type R on track with stock 0W-20 Honda or another Full Synthetic and documented conditions after their thicker break in oil has flushed out.

 

[Ktrw]

The K20C calls for 0W-20 at street driving temperatures. 0W-20 oil at track temperatures is a lower viscosity than what the engine was designed for. I'm going to keep saying this until the end of time lol. You continue to neglect this when recommending what is "safe".

 

[johnloov]

I appreciate your feedback. I’m just trying to only follow the data and lab results. I’m happy to correct conclusions with new data.

How many degrees did your car increase in water temps on track by switching from 0W-20 to 5w-30?

And to confirm, are you saying it’s safer to run higher engine temps on a stock type r fl5 running at 240F water temps with 5w-30 on track?

or it’s safer to run 0W-20 at 221F on stock FL5 type R.

Please technically describe what is safer. Many thanks!

I thought lower temps were better for the engine and engine oil performance.

 

[Xmetal]

I appreciate your feedback. I’m just trying to only follow the data and lab results. I’m happy to correct conclusions with new data.

How many degrees did your car increase in water temps on track by switching from 0W-20 to 5w-30?

And to confirm, are you saying it’s safer to run higher engine temps on a stock type r fl5 running at 240F water temps with 5w-30 on track?

or it’s safer to run 0W-20 at 221F on stock FL5 type R.

Please technically describe what is safer. Many thanks!

I thought lower temps were better for the engine and engine oil performance.

Just observing water/oil temps in a vacuum without taking into consideration of track ambient temperature is already flawed when comparing operating temps between 0w20 and 5w30. There are so many variables at play here.

 

[Ktrw]

Just observing water/oil temps in a vacuum without taking into consideration of track ambient temperature is already flawed when comparing operating temps between 0w20 and 5w30. There are so many variables at play here.

Agreed, I have not seen anyone test this properly or quantify the actual difference in the FL5/DE5. I understand it may be common knowledge that higher viscosity oils run hotter, which there is already a heat transfer difference between oils regardless of viscosity (race oils shown by Lake Speed Jr.), but I have not seen anyone show with good testing that the difference in a K20C being 10-15F oil and water temps.

I also happen to not care even if that were the actual dT because 0W-20 will be an insufficient viscosity at 240F+ even compared to 5W-30 at 250-255F+ going by those numbers. Not sure why you would care about oil temperature more than proper oil viscosity for the safety of the engine. The oil is going to break down faster at track loads and temps so that is a given. Modern synthetic oils can pretty easily handle sub 300F oil temps for short track OCIs. If you care about managing coolant temps and you track your car quite a bit in hot weather, GET AN UPGRADED RADIATOR. Don't try to band aid your cooling issue with your oil.

 

[johnloov]

Just observing water/oil temps in a vacuum without taking into consideration of track ambient temperature is already flawed when comparing operating temps between 0w20 and 5w30. There are so many variables at play here.

The dyno tests were done in the same ambient temperatures - same engines, different viscosity engine oils.

I'm a bit confused. 241F water temps seems super hot - that's almost 290F in real oil temps.

Had to throw this into AI to get a reality check as it's not making sense to me why I would go to a thicker oil on a stock FL5 Engine if it's going to make it run hotter on track. How is that protecting the engine?
=====================
Short answer: yeah—that’s hot.

On a stock FL5, 242 °F coolant usually puts bulk oil in the ~290 °F range. Modern SP synthetics can tolerate brief spikes there, but sustained operation in that band accelerates oxidation, thins viscosity, and risks pressure/bypass issues—i.e., not great for longevity.

Rules of thumb:

• Oil 220–250 °F = normal/happy
• 250–270 °F = caution; shorten stints/OCIs
• >270 °F sustained = back off or cool-down lap; watch hot oil pressure (the real safety metric)

If you’re seeing 242 °F coolant on comparable laps, the safer play is whatever setup keeps temps down (in your case, that’s been 0W-20 with good pressure) or add real oil cooling before stepping to 5W-30.

That's Zygrene's car - he even said it's way too hot. He also has the upgraded radiators.

https://www.sae.org/papers/investig...el-engine-2009-01-2686?utm_source=chatgpt.com

 

[johnloov]

This car was tested on a dyno, same day, same temps, same setup:

From that dyno sheet, and strictly looking at the data, the trend is clear:

• Coolest: Stock/0W-20 grades. Best-power temp was ~90–95 °C.
• Hotter: 5W-30 grades. Best-power temp shifted to ~100–105 °C.

So in this test the 0W-20 ran ~5–15 °C (≈9–27 °F) cooler than the 5W-30 oils. Also note the thicker oils showed slightly lower average power (205–206 kW vs 209 kW), which fits the “more pumping/friction → more heat” pattern.

Viscosity at 100°C (212°F) ASTM D445:

VOA of Honda 0w-20 7.99 mm²/s
VOA of Motul Power 0w-20 8.7 mm²/s
VOA of Motul Mugen 5w-30 10.5 mm²/s
VOA of Motul 300V 5w-30 11.0 mm²/s

• Best-power temps:
  
  • Stock/Honda 0W-20: 90 °C
  • Motul 8100 Power 0W-20: 95 °C
  • Mugen 5W-30: 100 °C
  • Motul 300V 5W-30: 105 °C
    ⇒ The 0W-20s make best power 5–15 °C (≈9–27 °F) cooler than the 5W-30s.
• Power: 0W-20 oils average ~209 kW, while the 5W-30s average ~205–206 kW (≈1.5–2% lower), consistent with higher pumping/friction losses on the thicker grades.
• Oil pressure: rises with viscosity (≈430–475 kPa on 0W-20 vs ~565–575 kPa on 5W-30), which aligns with higher circuit ΔP and helps explain the hotter “best-power” temps on the thicker oils.

Caveat: these are “best-power @ temp” points from a dyno session—not a steady-state cooling study—but the direction is consistent with what we discussed: thicker → more loss/heat; thinner (within spec) → cooler and equal or better power on a stock-cooled FL5.

 

[Ktrw]

This car was tested on a dyno, same day, same temps, same setup:

From that dyno sheet, and strictly looking at the data, the trend is clear:

• Coolest: Stock/0W-20 grades. Best-power temp was ~90–95 °C.
• Hotter: 5W-30 grades. Best-power temp shifted to ~100–105 °C.

So in this test the 0W-20 ran ~5–15 °C (≈9–27 °F) cooler than the 5W-30 oils. Also note the thicker oils showed slightly lower average power (205–206 kW vs 209 kW), which fits the “more pumping/friction → more heat” pattern.

Viscosity at 100°C (212°F) ASTM D445:

VOA of Honda 0w-20 7.99 mm²/s
VOA of Motul Power 0w-20 8.7 mm²/s
VOA of Motul Mugen 5w-30 10.5 mm²/s
VOA of Motul 300V 5w-30 11.0 mm²/s

• Best-power temps:
  • Stock/Honda 0W-20: 90 °C
  • Motul 8100 Power 0W-20: 95 °C
  • Mugen 5W-30: 100 °C
  • Motul 300V 5W-30: 105 °C
    ⇒ The 0W-20s make best power 5–15 °C (≈9–27 °F) cooler than the 5W-30s.
• Power: 0W-20 oils average ~209 kW, while the 5W-30s average ~205–206 kW (≈1.5–2% lower), consistent with higher pumping/friction losses on the thicker grades.
• Oil pressure: rises with viscosity (≈430–475 kPa on 0W-20 vs ~565–575 kPa on 5W-30), which aligns with higher circuit ΔP and helps explain the hotter “best-power” temps on the thicker oils.

Caveat: these are “best-power @ temp” points from a dyno session—not a steady-state cooling study—but the direction is consistent with what we discussed: thicker → more loss/heat; thinner (within spec) → cooler and equal or better power on a stock-cooled FL5.

Yeah I meant testing on track since that's what we're talking about. I saw the dyno testing video 2 years ago but I can see potential issues with the testing methodology in that video regarding test order and heat soak which could contribute to temperature differences. In some ways it would be easier to eliminate those uncontrolled variables by just observing on track temperatures back to back since there is a large environmental heat sink. Obviously on track there are other factors that could impact the results like change in ambient temperature but at least that can be taken into account when viewing results.

The takeaways given at the end of the video are still that higher oil viscosities are safer on track btw, so if you want to use that as a source, include that testimony. Proper oil viscosity allows for proper and stable oil pressure which is the best thing for your engine at high load.

Also don't think Zygrene has any engine cooling mods on his DE5 aside from a cooling plate since he's said that to me in replies.

 

[johnloov]

Yeah I meant testing on track since that's what we're talking about. I saw the dyno testing video 2 years ago but I can see potential issues with the testing methodology in that video regarding test order and heat soak which could contribute to temperature differences. In some ways it would be easier to eliminate those uncontrolled variables by just observing on track temperatures back to back since there is a large environmental heat sink. Obviously on track there are other factors that could impact the results like change in ambient temperature but at least that can be taken into account when viewing results.

The takeaways given at the end of the video are still that higher oil viscosities are safer on track btw, so if you want to use that as a source, include that testimony. Proper oil viscosity allows for proper and stable oil pressure which is the best thing for your engine at high load.

Also don't think Zygrene has any engine cooling mods on his DE5 aside from a cooling plate since he's said that to me in replies.

Thank you for those details. That seems correct.

When we met at Laguna Seca, Zygrene noted an immediate rise in temps after switching to 5W-30 Pennzoil Ultra Platinum (PUP).

Quick data request:

What maximum on-track coolant temps are you seeing, and what’s your setup (cooling mods, tune, oil grade/brand, ambient, stint length)?

Context:

FL5 Type R, stock cooling, 25-minute full-pace sessions; max coolant 221 °F at COTA. After a few oil changes (break-in oil removed) the car began running noticeably cooler. I used to see much hotter water temps and oil temps when the car had its original oil.

Question:

Any technical insight into why temps dropped—e.g., reduced break-in friction, less fuel dilution, or better oil-side heat transfer with a low-vis SP 0W-20? Many thanks.

Based strictly on the UOAs and dyno data, Motul 8100 Power and 8100 Eco-clean show excellent shear stability—they hold grade extremely well. There’s also a Texas owner who’s logged ~100,000 miles on Eco-clean in a modified Type R (and other tuned cars) with good results. Of the oils we've sampled, Motul 8100 Eco-clean and Power 8100 looks most shear-resistant so far.

My Honda Ultimate VOA is KV100 7.99 cSt; Eco-clean (API SP) is ~8 cSt new and publishes stronger hot-side metrics, so it’s the next oil I’ll test. It’s available on FCP Euro, which also offers a lifetime replacement program.

https://www.civicxi.com/forum/threads/-engine-oil-red-pill-thread-only-post-if-you-have-uoa-official-honda-civic-type-r-k20c1-engine-oil-analysis.57366/post-960151

https://www.civicxi.com/forum/threads/-engine-oil-red-pill-thread-only-post-if-you-have-uoa-official-honda-civic-type-r-k20c1-engine-oil-analysis.57366/post-960147

Also -

HPD (Honda Performance Development) K20C1 Engine Operating Specifications sheet for the U.S. F3 Americaspackage. It explicitly says:

• Oil type: 0W-20 Mobil 1 Advanced Fuel Economy or 0W-20 Phillips 66 Shield Valor — “No other oils are approved at this time.”
• Oil temp limits: normal 60–110 °C, max 115 °C (239 °F).
• Change interval: each race weekend / ~500 miles.
• Oil pressure targets: >3 bar idle; >5 bar above 5,000 rpm; not to exceed 7.5 bar.

So yes: for this racing K20C1 installation HPD specifies 0W-20, and the two examples they name are the same fuel-efficient formulations you can buy off the shelf.

This is also interesting - the Max Water Temp - matched my exact water temp at 221F at COTA last time also:

1) Physics (why 0W-20 can run cooler):

• The FL5 uses a gerotor (positive-displacement) pump. Lower viscosity reduces pressure losses in galleries and the oil-cooler circuit, so the pump delivers more usable flow.
• More flow raises the oil-side heat-transfer coefficient (h ∝ Re^0.8), so the system rejects heat faster. Thicker oil does the opposite unless you add serious cooling; it can also push the system onto relief/bypass, skipping the cooler.

2) Safety guardrail (when thicker helps):

• The right grade is the thinnest oil that keeps hot oil pressure in spec for the whole stint. If pressure is marginal (worn/looser clearances, very high bulk temps), a step up in viscosity can be safer—provided you upgrade cooling so you don’t just trade pressure for heat.
• Practical proxy inside 0W-20: choose higher-HTHS options (e.g., Motul Eco-clean ≈2.7, Motul RBS0-2AE ≈2.9) for more film strength without the temperature penalty of a 5W-30.

3) Evidence, not folklore:

• Your dyno & logs: best-power ~90–95 °C on 0W-20 vs ~100–105 °C on 5W-30, with ~1.5–2% lower power on thicker oil—consistent with higher pumping/friction and less cooler flow.
• HPD (Honda Performance Development) specifies 0W-20 (Mobil 1 AFE or P66 Shield Valor) for the racing K20C1 package with tight temp control and short drains—proof the concept is valid when pressure is maintained.

4) Method concerns & how to test right:

• Heat-soak/order effects are real. Do back-to-back on-track A/B the same day: equal fuel & fill, same driver/pace, log coolant, gallery/sump oil temp, and hot oil pressure, plus ambient. Compare stabilized last-3-lap averagesand report the ΔT and pressure.

Bottom line: For a stock-cooled FL5 that holds pressure on 0W-20, 0W-20 is both cooler and safer for HPDE at short OCIs. If pressure isn’t in spec, add cooling first—then consider viscosity.

This seems logical, and my data matches exactly the data from Honda Racing. My max water temp was also 221F. It seems that the Best Goldilock zone for the stock FL5 is to run the highest sheer strength 0W-20 and change it often.

So the question is.... Is thicker oil, on a stock car, the reason why a lot of FL5 Type R owners are overheating their cars on track?

The data sure suggests that right?

Why is my car not overheating anymore after I flushed out the break-in oil?

 

[johnloov]

Lakespeed Junior with speed diagnostics also validated the oil temp jumps.

---------------------

John,

I don't have all of the dyno data handy, but when we would switch from a 0W-30 to a 20W-50 the water temp changed about 10F and the oil temp difference was nearly 30F. Between a 10W-40 and 15W-50 we typically saw a 5F water temp difference and the oil temp would drop by about 20F (with the lower viscosity oil).

--
Lake Speed Jr.
[email protected]

-------------------------------

I found this experiment super fascinating, as everyone is telling me to run thicker oil, but if you're overheating your engine, I assume that's not more protection, that's less, right!?

--------------------------------

Correct. Hotter temp = less protection.


Lake Speed Jr.
[email protected]

 

[Ktrw]

Lakespeed Junior with speed diagnostics also validated the oil temp jumps.

---------------------

John,

I don't have all of the dyno data handy, but when we would switch from a 0W-30 to a 20W-50 the water temp changed about 10F and the oil temp difference was nearly 30F. Between a 10W-40 and 15W-50 we typically saw a 5F water temp difference and the oil temp would drop by about 20F (with the lower viscosity oil).

--
Lake Speed Jr.
[email protected]

-------------------------------



--------------------------------

Correct. Hotter temp = less protection.


Lake Speed Jr.
[email protected]

0W-30 to 20W-50 is like an 8.2cst jump in viscosity (insanely high) using the average of each range. 10W-40 to 15W-50 is abou a 4.7cst jump. 0W-20 to 5W-30 is about 2.8cst. So both of those are quite a bit higher than the 0W-20 to 5W-30 jump I've been talking about. Even street driven, my PUP 5W-30 result was only 1.3cst higher than PUP 0W-20 and was actually in the 20 grade range at the end of my OCI.

Referring to the dyno video results, you said, "The 0W-20s make best power 5–15 °C (≈9–27 °F) cooler than the 5W-30s.", which I think may be more accurately around 15°F end of the spectrum since going from a 30 to a 50 grade was a 30°F difference according to Lake. Based on what Lake said and the dyno video, the coolant temps would be hardly different since a larger increase in viscosity was only a 5°F coolant temp difference, and probably around a 15°F difference in oil temps using a linear relationship for those two data points.

Would still rather run something like PUP 5W-30 at 15F higher oil temps than 0W-20 on track, so long as the UOA also comes back clean. My street-driven UOAs are fine on both, so I'd rather have the extra protection from the viscosity.

 

[johnloov]

Fair points. If you are not overheating on track and you're at 5-6ppm aluminum or lower in your UOA, then 5w-30 PUP seems fine.

 

[johnloov]

Here's an interesting paper on this topic:

Extending lubricant life

Controlling operating temperature of the lubricant is important to minimizing oil oxidation.

Heat erodes protection non-linearly: Oxidation follows Arrhenius—roughly ~2× faster per +10 °C (18 °F)—so 258 °F ages the oil much faster than 243 °F, and viscosity drops with temperature, shrinking any thickness advantage the 5W-30 had on the label.

"Oxidation reaction rates double or triple for every 10 C increase in temperature. Thus, a reaction rate of unity at 70 C will increase between 2 and 3 at 80 C, between 4 and 9 at 90 C and between 8 and 27 at 100C and so on."

https://www.stle.org/images/pdf/STLE_ORG/BOK/OM_OA/Additives/Extending Lubricant Life_tlt article_Nov09.pdf

So for your example: 0W-20 at 243 °F vs 5W-30 at 258 °F—the cooler 0W-20 is the safer operating point if hot oil pressure is in spec, because you’re avoiding the oxidation/viscosity loss penalty while maintaining film via temperature and flow.

This is maybe why that Honda race car is using 0w-20 and changing it after a race weekend.

The Spoon FL5 Type R is running 25 hour races, that has a modified engine and serious cooling, stock turbo, does run a PAO 5w/30.

Basically - the moral of the story story is - don't cook your engine oil above these ranges, as it's now looking questionable if it protects your engine better to go up in thickness and run hotter.

If you're running a higher weight oil, you absolutely need effective dual oil coolers it looks like.

 

[Ktrw]

Here's an interesting paper on this topic:

Extending lubricant life

Controlling operating temperature of the lubricant is important to minimizing oil oxidation.

Heat erodes protection non-linearly: Oxidation follows Arrhenius—roughly ~2× faster per +10 °C (18 °F)—so 258 °F ages the oil much faster than 243 °F, and viscosity drops with temperature, shrinking any thickness advantage the 5W-30 had on the label.

"Oxidation reaction rates double or triple for every 10 C increase in temperature. Thus, a reaction rate of unity at 70 C will increase between 2 and 3 at 80 C, between 4 and 9 at 90 C and between 8 and 27 at 100C and so on."

https://www.stle.org/images/pdf/STLE_ORG/BOK/OM_OA/Additives/Extending Lubricant Life_tlt article_Nov09.pdf

So for your example: 0W-20 at 243 °F vs 5W-30 at 258 °F—the cooler 0W-20 is the safer operating point if hot oil pressure is in spec, because you’re avoiding the oxidation/viscosity loss penalty while maintaining film via temperature and flow.

This is maybe why that Honda race car is using 0w-20 and changing it after a race weekend.

The Spoon FL5 Type R is running 25 hour races, that has a modified engine and serious cooling, stock turbo, does run a PAO 5w/30.

Basically - the moral of the story story is - don't cook your engine oil above these ranges, as it's now looking questionable if it protects your engine better to go up in thickness and run hotter.

If you're running a higher weight oil, you absolutely need effective dual oil coolers it looks like.

Yup that is line with what Lake Speed has said regarding oil oxidation. You should be changing your oil in very short intervals with track days anyway so I don't think oxidation is the limitation with good synthetic oils. 5W-30 will oxidized faster if it's at a higher temperature but it will still provide higher and more stable oil pressure to go along with the additional viscosity.

If you're not using speed diagnostix for your UOAs you probably have no idea what your oil oxidation is anyway. My 5W-30 oxidation value was 4% higher than my 0W-20 result with 30% more miles on it and the same driving habits. Obviously at track temps the oxidation value may increase more relative.

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