Shel_B
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... in slow motion.
Why Do Knowledgeable Folks on Here use 20 wt Oil
- Thread starter Al
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The rules make it simple it sounds like and I haven't spent any time looking at them...just going off what I was told. You have to run the oil specified by the OEM in his spec racing class. SCCA has lots of rules that can seem odd or ridiculous but they are what they are and attempt to make it even/fair. Follow them to be cheat-free. Easy. It's a 106 hp NA Fit.
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Meanwhile I'm here at 270+ haha
With high HTHS viscosity 5W-40. Try some 0W-20.
Yeah, that's the beauty of them, they don't weigh anything or make any power. And it's a honda. Barely need oil regardless of the viscosity.
I'm sure HPL has no issue with that. My experience killing and rebuilding my last motor suggests that the rings might be the weak point for heat, stock gap is very tight. Temperatures and shear rates are also very high in this area.
With high HTHS viscosity 5W-40. Try some 0W-20.
I think I found the video you mentioned. It was not a Supra, it was a GR86. The reason they pulled the oil pan after a track day was because of the excessive RTV clogging up the pickup. The design of that motor/sump is also just prone to oil pressure loss. Didn't look like they ever pulled the rod bearings. Maybe there's a different video but I don't remember any of their videos mentioning 5w-20.
Minimum Oil Film Thickness headroom is a good thing. Even for other lubricated parts ... not just journal bearings.
Effect of low viscosity oils on engine bearings.
https://www.substech.com/dokuwiki/doku.php?id=effect_of_low_viscosity_oils_on_engine_bearings
Scroll down to the section: "Effect of Oil Viscosity"
https://www.substech.com/dokuwiki/doku.php?id=oil_clearance_and_engine_bearings
Effect of low viscosity oils on engine bearings.
https://www.substech.com/dokuwiki/doku.php?id=effect_of_low_viscosity_oils_on_engine_bearings
Scroll down to the section: "Effect of Oil Viscosity"
https://www.substech.com/dokuwiki/doku.php?id=oil_clearance_and_engine_bearings
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wemay
Site Donor 2023
Outside the laboratory testing, going from a 2.6 HTHS 0w20 to a 2.9 HTHS 5w30 is negligible. The real difference will come in-to-play when you move up to a 3.5 HTHS.
The same goes for MPG. In the lab, yes, there's a difference. Real world? Negligible.
Excluding those running a 3.5 HTHS, everyone else here may be fooling themselves into feel-good assurances.
The same goes for MPG. In the lab, yes, there's a difference. Real world? Negligible.
Excluding those running a 3.5 HTHS, everyone else here may be fooling themselves into feel-good assurances.
wemay
Site Donor 2023
Historically yes but back when every brand was still posting their HTHS, many had gone down to 2.9 and 3.0. The only 3.2 I remember was Valvoline SynPower. Now, hardly anyone posts this in their TDS (along with Noak). I suspect that's because they've thinned down. Just speculation on that part.
I remember back in the 70's. 20w20 was a oil used in cars and gasoline tractors. 10w in the winter and 30w in the summer. But alot of people used 20w.
4WD
$50 site donor 2025
Yep, like the valve train in modern engines …
4WD
$50 site donor 2025
The fuel saving starburst era - the counter ‘robust’ oil here used to be M1 10W30 HM
Yes, I’m running Amsoil SS 0w30 and it’s just under 3.1; while their 5w and 10w options for SAE 30 are right there.
For my Fit, I doubt much measurable wear rate difference has occurred running a 20 grade for its first 300k, there simply isn’t enough power made and the oil temps are mild; thus the ridiculously easy to extend intervals.
Instead, I think rings becoming stuck and which synthetic I’ve used has been a bigger factor to long term engine health due to running minimum spec OTS oils too far; while understanding now they aren’t all able to “run clean” especially typical Grp III with lots of moly and poor quality VII and base oils that aren’t up to regularly extended intervals.
Cleaning with VRP or continued use with Amsoil doing so; should give conclusive data for that suspicion. For now it’s speculation and anecdotal fwiw.
So, if I had run exclusively M1 EP or Amsoil SS or HPL for the typical 9k-12.5k intervals I was doing; instead of M1 AFE for 10k-15k (a couple times), the Chevron Havoline Pro DS for 10k (which I regularly used Lugebard’s blue BT additive for both those oils)…I wonder, would it have developed a rear main seal leak or started consuming oil? Simply going up to SAE 30 wouldn’t have prevented that. UOAs looked fine, but do they really show what’s happening to the rear main or deposits in the oil control rings?
After the consumption increase and rear main leak started, I changed to HM oils without much success. My main regrets are using LG’s additive and extending the intervals; as well as oil choice. I’d go back and stick to EP or SS without additives if I could.
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My oil pump would need to be using >>3% of engine output in order for a one grade change in oil to make a 3% difference. It's wild to me how much work folks imagine their oil pump is really doing. "Sure starts easier with that 0w-XX."
Zeeooohsix will love this:
Melling LS pump, advertised as 7.5 gpm at 2000 rpm. On a 5 qt pan, it cycles/clears the sump every 10 seconds. Sounds fast, but reasonable.
If it's making 45 psi cruising at 2000 rpm...
Then we're looking at roughly 0.20 hp of mechanical work (ideal) being done. Even if the pan is only 10% efficient, its using 2 hp.
So how much of that 2 hp are we going to eliminate to gain a 3% increase? A quarter? (pressure drop from 45 psi to 33 psi, which we know is unrealistically large for a one grade drop). So 0.5 hp gain. That would be a 3% improvement if we are cruising at 17 horsepower output.
In reality we know the efficiency of the pump is >10%, the decrease in work (associated with lowering of pump pressure output) would be less than 25%, and the cruise output is greater than 17 hp. So gains would be far less than 3%. 3-6% estimated improvement from 30 wt (~10 cSt?) to 20 wt (~8 cSt?) doesn't pass the sniff test.
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Yes, Valvoline seems to have decent HTHS vs viscosity grade. Someone contacted Valvoline and per this posts in the VRP thread, the VRP 5W-30 has a HTHS of 3.24 cP. An added bonus to VRP.
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Ok, what other maintenance habits? Length of OCI, conditions driven? Can’t be the only difference.
Ah yes ... the graph I posted in a one of those dead horse beating threads on PD oil pump operations, lol.My oil pump would need to be using >>3% of engine output in order for a one grade change in oil to make a 3% difference. It's wild to me how much work folks imagine their oil pump is really doing. "Sure starts easier with that 0w-XX."
Zeeooohsix will love this:
Melling LS pump, advertised as 7.5 gpm at 2000 rpm. On a 5 qt pan, it cycles/clears the sump every 10 seconds. Sounds fast, but reasonable.
Whatever the HP and fuel mileage savings claim is due to running a thinner oil, it comes from a combination of both less oil shearing and less oil pump input power to pump the oil through the system. Yes, the claim of 3% to 6% increase in fuel mileage (wherever that came from) is obtained by going down from xW-30 to xW-20 is way too high.
Yes, the hydraulic HP required is small. The HP equation above is for a 100% efficient pump ... your favorite "pump slip" stuff, lol. You have to divide by the pump efficiency to be totally accurate. But healthy automotive PD pumps are in the 80-85% efficiency range, so it wouldn't make much difference here. So, (7.5 x 45)/(1714 x 0.85) = 0.232 HP.If it's making 45 psi cruising at 2000 rpm...
Then we're looking at roughly 0.20 hp of mechanical work (ideal) being done. Even if the pan is only 10% efficient, its using 2 hp.
"Even if the pan is only 10% efficient" ... you mean pump I assume.
If you assume the oil pump was not in relief (to make this example simpler), and the pressure at 2000 RPM went down from 45 PSI to say 40 PSI due to a decrease in oil viscosity, then the delta in required pump input HP would be as show below. If the pump is in relief, then you'd have to know the actual flow vs pressure curve of the pump as the RPM increases while in relief as shown in the Melling pump graph.
(Q x P)/(1714 x E) = Pump HP
(7.5 x 45)/(1714 x 0.85) = 0.232 HP
(7.5 x 40)/(1714 x 0.85) = 0.206 HP
So it's only saving 0.026 HP, which is a 11.2% decrease from 0.232 HP.
An average car cruising down the road at 60 MPH needs approx 23 rear wheel HP (26 crank HP). That includes the HP to over come aerodynamic and rolling resistance.
So the actual realized delta pump HP savings on the system by going with a thinner oil is 0.026/26 = 0.1%. In other words wrt to the pump HP in this example, going with a thinner oil only saved 0.1% of the HP at the crank to move the car at 60 MPH.
The other crank HP savings would come from the reduced oil shearing, which this example doesn't account for. So maybe add another few tenths of a percent for the total savings. It's still a very small savings. Yeah, it doesn't pass the sniff test, or the calculation test.
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There's way more to the story I'm sure for the real reasons they had engine rebuilds. No car blows up engines by using a thicker oil than 0W-20. You think Ford would specify 5W-20 and also 5W-50 for same engine like the Coyote V8 if that thick oil would damage the engine. On the other hand, using 0W-20 for heavy track use could actually damage the engine, and as a minimum cause more engine wear.
Yeah, the stuff that gets thrown in sometimes is just random nonsense, kind of like "Pennzoil killed my engine". Maybe he's that guy.
Don't you know how magical 0W-20 oil is? It saves engines from the evil 40-grade!
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