Viscosity breakdown a problem or no?

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Mar 20, 2022
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Hello folks,
I have been running Castrol Edge 5w-40 in my 2018 VW Golf R for a few years now. All the oil analyses show a lower viscosity than other reports I'm seeing. It's probably because I do a lot of short trips in this car, and somehow the fuel burns off by the time I do the analysis? This last time was especially bad because it was during pandemic and so I didn't change the oil for 1.5 yrs. Anyway, is this viscosity breakdown a problem, and if yes, should I try a different brand of oil? Or change more frequently? I will try the 0W-40 next because many people here say it is "better".


blackstone.jpg
 

FZ1

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Hello folks,
I have been running Castrol Edge 5w-40 in my 2018 VW Golf R for a few years now. All the oil analyses show a lower viscosity than other reports I'm seeing. It's probably because I do a lot of short trips in this car, and somehow the fuel burns off by the time I do the analysis? This last time was especially bad because it was during pandemic and so I didn't change the oil for 1.5 yrs. Anyway, is this viscosity breakdown a problem, and if yes, should I try a different brand of oil? Or change more frequently? I will try the 0W-40 next because many people here say it is "better".


View attachment 93548
Looks good. 9.86 is plenty of vis to keeps the parts separated. Jmo
 
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I will echo what @Rand said. Blackstone has a number of categories (TBN too) that are wildly inaccurate. I would try Castrol's 0w40 for a shorter interval, myself. Nothing wrong with Castrol 5w40, it's just the 0w40 is a slightly superior oil for the same coin, so why not?

BTW, nice car! Any modifications done to it? Or is it as delivered?
 

beanbag137

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yes, it's tgdi engine.
Even if Blackstone's fuel dilution number is off, the flashpoint is still kind of high, so probably no actual fuel?
First column is original VW break-in oil. Everything afterwards is Castrol 5W-40 (what they fill at the dealer anyway).
Only minor mods to the car like clutch pedal damper removed, full size spare in trunk, different wheels.
 
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yes, it's tgdi engine.
Even if Blackstone's fuel dilution number is off, the flashpoint is still kind of high, so probably no actual fuel?
The two are tied together. Blackstone infers fuel dilution based on the flash point, which in and of itself has a high reproducibility and repeatability tolerance. Blackstone has shown to be wildly inaccurate in estimating fuel dilution based upon their measurement of flash point.
 

OVERKILL

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Regarding flashpoint:

There are two different methods used:
ASTM D92 - Open Cup
ASTM D93 - Closed Cup

Closed Cup produces lower numbers because vapours can't escape. Some blenders use one or the other exclusively, some mix it up on the fly. If we look at the PDS for Castrol Edge 5w-40 A3/B4, it shows 208C (406F), but that's D93. In comparison, Mobil's Formula M 5w-40 shows 228C (442F) but that's D92.

Blackstone uses D92:
Screen Shot 2022-03-21 at 11.40.03 PM.jpg


So, if your lube had a D92 FP closer to that of the Mobil product, then it has dropped 40F.

Blackstone apparently keeps a table of "should be" values, but I have no idea how well maintained it is and what we see from them vs what we see from labs that use GC really gives me zero confidence in their ability to properly gauge fuel content in these samples.
 

beanbag137

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How do I tell if I have a fuel dilution problem, or a shear viscosity breakdown problem?
 

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OVERKILL

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How do I tell if I have a fuel dilution problem, or a shear viscosity breakdown problem?
A good UOA that uses an accurate method/standard to measure fuel dilusion (not Blackstone).

^This. Polaris/OAI are a good choice. You can buy the OAI kits from the AMSOIL website.
 
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I will echo what @Rand said. Blackstone has a number of categories (TBN too) that are wildly inaccurate. I would try Castrol's 0w40 for a shorter interval, myself. Nothing wrong with Castrol 5w40, it's just the 0w40 is a slightly superior oil for the same coin, so why not?

BTW, nice car! Any modifications done to it? Or is it as delivered?
How is the 0W40 a "slightly superior oil"? Serious question.
 
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Any polymers will squeeze to a temporary thinner viscosity and return to normal. The less polymers the better even if they do not permanently shear. But high quality polymers do not permanently shear. (star polymers?) Fuel dilution can be burned off with a long drive.

The wider the gap in viscosity filled with polymers. Base oil choice… higher base oil VI without VII.
 
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OVERKILL

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How is the 0W40 a "slightly superior oil"? Serious question.
The Castrol 5w-40 uses no PAO in the base oil blend, while their 0w-40 is ~50% PAO.

The 5w-40 has the following approvals:
A3/B4
API SL
BMW LL-01
MB 229.5
VW 502.00/505.00

The 0w-40 has the following approvals:
A3/B4
API SN/CF
Ford WSS-M2C937-A
MB 229.3/229.5
Porsche A40
VW 502.00/505.00

No 0w-40's have LL-01 anymore, BMW doesn't approve them. The addition of A40 on the 0w-40 is probably the biggest stand-out.
 

FZ1

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How do I tell if I have a fuel dilution problem, or a shear viscosity breakdown problem?
Re shearing: I think it's more what, than why. You just want sufficient vis to keep the parts separated. I don't want any oil, at less than 7.5 , exiting my 0w-20 spec '17 Camry. Jmo
 
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beanbag137

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ok, I will get an amsoil analysis then.
My oil temps at the end of my short commute range from 170 to 210. The normal operating temperature is around 220, so I know the oil is not reaching full temperature. Is there a cumulative, permanent degradation in viscosity from having fuel in the oil, or is everything back to normal after just one long drive?
 
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First column is original VW break-in oil. Everything afterwards is Castrol 5W-40 (what they fill at the dealer anyway).

Very most probably first two aren't Castrol. I don't remember seeing any Castrol with 300 ppm of Boron (if any).

I agree with all BS being notoriously inaccurate both in fuel dilution and viscosity, so don't overerstimate these results. That said, swapping to Castrol Edge 0W-40 is probably a good idea, however personally I'd consider M1 ESP 5W-30 and ESP X3 0W-40 if you can obtain them for an acceptable price. Or Ravenol VMP, REP and RUP.
.
 

beanbag137

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Well, what can I say. The first oil analysis is factory fill oil. The next three are from the VW dealer, which claim Castrol Edge 5W-40 on the receipt.
The next fill, I did it myself and got a jug of also Castrol Edge 5W-40 from Walmart. I did a Horizon / Oil Analyzers test on it after 5500 miles:

horizon OALpng.jpg


The viscosity, while higher than the Blackstone values, is still on the low side, while at the same time, fuel dilution is not bad. So what does this mean?
Also, this is the first time I got a significant titanium reading. Maybe I got the "fluid titanium" version from Walmart? (I threw away the jug already so can't confirm)

P.S. This test report is wrong in that I only added 0.3 qt make up oil. Though this is the first time my car burned any oil since new. Hmmm....
 
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