UOA mix oil Audi A3,Audi A4 2.0TDI

[Pedro I]

Hello, I have used analysis of my two cars, Audi A3 and Audi A4, both have the same 2.0 TDI EA 288 euro 6 engine. The kilometers of the intervals are similar 4700 and 4900 km, the operating hours vary slightly 111 and 85 respectively.
I have a question that I do not understand, the two cars had exactly the same oil, the same viscosity 5w40 viscosity at 100° of 12.8cst, in the cases there was dilution of 4 and 2% and the analyzes show viscosity of 11.1 and 11.3 cst. It is assumed that with more amount of fuel the viscosity should be lower, however the two samples will show almost the same viscosity.
It seems that the dilution affects the viscosity regardless of the amount of fuel, could it be related to the thickening polymers that degrade with the fuel?

 

[930.engineering]

It seems that the dilution affects the viscosity regardless of the amount of fuel,
could it be related to the thickening polymers that degrade with the fuel?

IMHO not worth writing home about. Fuel and viscosity numbers are
notoriously unreliable. Result are pretty solid regardless. That's what
matters. 3,9 l/100 km is strong too! Not suprising it's the car with the
higher average speed/less hours, apparently because less city driving.
.

 

[Pedro I]

Well, we will see shortly the following analyzes how they evolve. I think that the fuel measurement is quite reliable because the A3 never completes the DPF regenerations completely and they are almost always interrupted, which means that more fuel enters the oil, in the case of the A4, the DPF regenerations are controlled and always completed and therefore there is less fuel entering the oil. In addition, the A3 regenerates every 200-250km on average and the A4 is every 480km in a fixed period, of so that by regenerating more often there is almost certainly more fuel input. I was observing some analyzes of this EA 288 engine and indeed this dilution tendency is present in all but also that it does not matter if it is 2% or 4% of fuel there is a Viscosity drop that has no correlation with the % of fuel.