Thick vs thin debate...

Yes, beating a dead horse here. I’m not looking for an argument but am curious. It is often cited here that engines can handle running a wide viscosity range of oils, which I agree with. But for some reason 0w20 (or thin oils in general) are viewed as the devil and shouldn’t be used in engines that previously specified a higher viscosity.

Example: the VW / Audi 1.4 TSI and 2.0 TSI. They previously ran 502.00 (30-40 grade) but now run 508.00 (0w20). So again, if engines can handle operating under such a large viscosity range (think thick oil when cold and thin when hot, which is quite the spread in CST measurement, and they DO handle that viscosity difference well)...why would it be detrimental to that engine to drop the grade down to a 20 from a 30? That is only a few CST thinner at operating temp (12 cst for 30 and 7ish cst for 20). That seems negligible IMO

Honest question.

VW explicitly advises, VW508.00 (0W-20 or 2.6 HTHS) is not to be back-spec'd to vehicles spec'd to run 502/505 (3.5 HTHS). Even in the same engine class.
 
Last edited:
What does VW specifically says in manual?
It doesn't mention it in the manual. It was read on the oil manufacturer websites that offer VW508 oils. Something to the effect of "Don't use 508 in Volkswagen which require 505/502 because 508 is not a back spec for those vehicles".
 
Last edited:
It doesn't mention it in the manual. It was read on the oil manufacturer websites that offer VW508 oils. Something to the effect of "Don't use 508 in Volkswagen which require 505/502 because 508 is not a back spec for those vehicles".
And where it says that? Bcs. Castrol recommends VW504.00/507.00 in Europe for this engine.
Can you give us link?
 
And where it says that? Bcs. Castrol recommends VW504.00/507.00 in Europe for this engine.
Can you give us link?

1. Not talking about other countries
2. I never said vehicles recommending 508.00 cannot use thicker oils. I do it all the time
3. What i said is below.



1611095503407.png



1611095797570.png



1611095962944.png



1611096065373.png





...and in the UK/Ireland, ESP X2 is us used in the 1.4T as well. 😉

1611099753942.png






...and in France


1611100349486.png




Also in Germany

1611101374514.png
 
Last edited:
A reputable engine builder did a back to back test with a 400hp V8 in Australia with 5w40 and 5w30 on an engine dyno, there was a difference of 6hp. He did at as a proper test, not to sell anything.
Good to hear some real figures, that is a 1.5% difference.

My old family 4-banger produces 90 kW on regular 91 RON fuel (86 AKI), and 92 kW on premium 95 RON petrol (90 AKI gas). So the documents say. That is a 2.7 hp increase or 2.2% difference. Plus a bit better fuel economy, but more expensive fuel.

That’s probably BITOG for you, a lot of fiddle-arsing about for 1 or 2% this way or that way.
 
Good to hear some real figures, that is a 1.5% difference.

My old family 4-banger produces 90 kW on regular 91 RON fuel (86 AKI), and 92 kW on premium 95 RON petrol (90 AKI gas). So the documents say. That is a 2.7 hp increase or 2.2% difference. Plus a bit better fuel economy, but more expensive fuel.

That’s probably BITOG for you, a lot of fiddle-arsing about for 1 or 2% this way or that way.
Not to mention the heated arguments over such minutiae. Lol.
 
That's reasonable. In what I've seen on the dyno, it's ~1% for every 4-5 cSt increase in viscosity. This is rough though and is dumbed down from HTHS which was the greater factor in power loss. The higher the HTHS, the sooner the rings transition into full fluid lubrication regime, but also the power loss increases exponentially as piston speed increases. In a certain 358ci V8, the difference between a 0w-20 (HTHS = 2.7 cP) and a 5w-30 (HTHS = 3.4 cP) was double digits at 8000 rpm and 280°F sump temp. Blow-by also increased due to the increased film thickness causing ring flutter above 8000 rpm. This is not a casual commuter engine though.

good info!

I would have guessed less blow-by with the increased film thickness ... but I'm just an oil user and not an engine designer.
 
Didn’t get a raise, huh? I’d say you did pretty well compared to so many people who lost jobs completely, shut down their business and buried loved ones. Guess you will have a bad summer vacation too with the travel restrictions.
Wasn’t saying that for anything more than to make the point that 40% isn’t negligible. Enough said.
 
1. Not talking about other countries
2. I never said vehicles recommending 508.00 cannot use thicker oils. I do it all the time
3. What i said is below.



View attachment 41482


View attachment 41484


View attachment 41485


View attachment 41486




...and in the UK/Ireland, ESP X2 is us used in the 1.4T as well. 😉

View attachment 41494





...and in France


View attachment 41499



Also in Germany

View attachment 41504
Good info, thanks for sharing. Again, this isn’t an “only in the US” spec.
 
Back
Top