V100 viscosity discrepancies

[3516]

Am using a 5W40 from a boutique blender the TDS shows a cSt at 100 c of 14.4

I've had two used sample reports come back from oil brought 12 months apart with V100 showing
12.5 after 6500km and 12.86 after 3600km on the second sample with the lab stating viscosity lower than the specification for the reported oil, incorrect oil grade reported.

Fuel dilution is under 2% and all other numbers are looking good.

Spoke to the companys lube tech line and they lodged a query with the formulation department but they seemed unconcerned with the lower readings in comparison to the TDS.

aside from the TDS data sheet on viscosity being incorrect ( I did raise that over the phone) why else would the oil drop viscosity so quickly without contamination

 

[Jetronic]

2% has a big impact on viscosity, but besides that multi grade oils do shear permanently in use, this will happen quickly after first use.

But most importantly, the TDS shows typical values, which means you can easily get 10% lower or higher, if not 20% Only very few companies show an acceptable range for those figures, though it's a lot like torque specs: if 77Nm is specced, 70-84Nm is usually allowable.

I wouldn't worry too much about it, did you get flash point numbers aswell?

 

[kschachn]

Which laboratory are you using and by what method is fuel dilution being measured? Post the actual analysis please.

Jetronic is making a good point above about typical values. Some blenders only report the limits of a license or approval not even test values. Which oil is this? Which vehicle?

 

[3516]

It is a large Caterpillar certified Lab, I'm not doubting the Lab results.

The oil is HPR5 from Penrite.
Vehical is a Turbo Diesel Ford Ranger.

I suspected it was shearing down and its base oil is probably on the lighter side with VII ?? As the company also has a 5W30 with what looks to be a similar additive package.

mostly just trying to understand the drop is viscosity as the lab is obviously using the Data sheet to get its baseline from which kinda explains why they are telling me I've reported the incorrect oil

Will stick up the report when im on the laptop next

Thanks

 

[kschachn]

It is a large Caterpillar certified Lab, I'm not doubting the Lab results.

The oil is HPR5 from Penrite.
Vehical is a Turbo Diesel Ford Ranger.

I suspected it was shearing down and its base oil is probably on the lighter side with VII ?? As the company also has a 5W30 with what looks to be a similar additive package.

mostly just trying to understand the drop is viscosity as the lab is obviously using the Data sheet to get its baseline from which kinda explains why they are telling me I've reported the incorrect oil

Will stick up the report when im on the laptop next

Thanks

The method is critical. Even a certified lab may use the ASTM method of estimating fuel based on flash point unless you're paying for a direct measurement such as gas chromatography. Flash point measurement has an inherently variable reproducibility and then when used to estimate fuel dilution it becomes even more inaccurate. There may very well be mechanical shear of the VII (nearly all oils use them unless its a monograde) but it's highly dependent on engine design and VM quality.

 

[twX]

If you use a viscosity mixing calculator, assuming a KV100 of 0.5 cST for gasoline, that oil would thin to around 13.35 cST from the fuel dilution alone. So less than half of the viscosity loss is from permanent shearing.

All else being equal, a 5W-40 will have more permanent shear-thinning than a lower-VI oil like a 5W-30 or 10W-30. Some oils use types of VII that are more resistant to shear-thinning.

 

[fantastic]

Sounds like you're comparing UOA to a VOA spec sheet. Those Spec sheets usually don't test the same & are usually lower than stated. Different lab variance. Sounds like the oil was ok & it should work well for your Ranger.

 

[3516]

Cut of last sample

 

[3516]

Sounds like you're comparing UOA to a VOA spec sheet. Those Spec sheets usually don't test the same & are usually lower than stated. Different lab variance. Sounds like the oil was ok & it should work well for your Ranger.

Yes, was comparing against the manufactures Spec sheet, and i guess the Lab is as well.
This was basically the thoughts of the Lube tech i spoke to, that it's Lab and blending variances a 10-12% discrepancy is not a concern for them, they suggested sending in a VOA of the oil to the same lab.

I thought i was just over thinking it.

Thanks for the feedback