RNT and Oil Specs

[AndyH]

The use of RNT - radionuclide wear testing - by VW in newer oil specifications comes up here from time to time. Some suggest it proves that the 506.0x oils are better than 505.01 - based on the use of the test.

I'd like to suggest that the use of a test - even RNT - doesn't prove the superiority (or inferiority) of a lubricant. Knowing the results of RNT testing for different formulas can, but we don't have the test results (or VW's limits for the different specs) - we just know the test is used.

Why is it used? Because it allows a lab test to give wear feedback in a shorter time than doing long-term fleet testing. In other words - it's less expensive, and can give faster feedback.

From one lab's web page:
"The 2007 and 2010 diesel engine emissions regulations are causing diesel engine manufacturers to use nonconventional engine control strategies that employ heavy exhaust gas recirculation (EGR) and include early and late fuel injection. Because these strategies might have a negative effect on engine wear and, subsequently, blow-by and loss of oil control, manufacturers need to assess their impact before engines are put into production. Using radioactive tracer technology, these assessments can be obtained in weeks rather than months or years."

According to the articles I've found, RNT is at least a 50 year old process. The Southwest Research Institute has been using it for about 50 years.

Here's some info from SwRI:

RNT Overview webpage:
http://www.swri.edu/4org/d03/vehsys/radtrace/default.htm

And a more in-depth paper:
http://www.swri.org/4org/d03/vehsys/radtrace/RadioactiveTracerTechnology.pdf

And an overview of one of the processes:
http://www.swri.edu/4org/d03/vehsys/radtrace/rattpaper.pdf

Andy

 

[nortones2]

it wasn't used by VW, but Castrol, and some of the engines in their road fleet subject to RNT had been running for 3 years, and some for 5.

 

[AndyH]

it wasn't used by VW, but Castrol, and some of the engines in their road fleet subject to RNT had been running for 3 years, and some for 5.

Absolutely. I figured I'd give VW credit for requiring RNT in their specs. I don't know how the VW lab is configured, so don't know if they do RNT in Wolfsburg. Some of the oil and additive companies use it, as do some independent labs.

I'd at least like to communicate that it's not a 'VW-centric' test - it's been in use for many years before the PD designer ever put pen to paper.

Though not required for the API/CJ-4 spec, it appears to have been used for development of the US's new HD diesel spec.

Here's what I have on specs. I don't have any data on 507.00 yet.

 

[wjdell]

Thanks for your effort Andy -

 

[TwoSlick]

Note the HT/HS visosity range for VW 506.01 oils, ie 2.9-3.4 Centipoise (Cp) @ 150C. That's pretty thin to use in a turbocharged diesel engine with direct acting camshafts, a fairly radical cam lobe profile and no rollers in the valvetrain. For comparion, most xw-40, HDEO's like Delvac 1 and the new Amsoil 5w-40 have HT/HS viscosities in the 4.2-4.5 Cp range @ 150C.

My caveat about using very thin oils in the TDI (all versions) still remains...it's fine if your engine is stock AND generates low levels of soot, but it's ill advised for first generation (96-99) TDI engines and modified engines that are chip tuned and/or have oversized injectors.

Finally, I find it interesting that the VW 506.01 lubes do not appear to have a specific limit on sulfated ash? I know the generic ACEA B3/B4 specs capped SA @ 1.6%. So you're certainly not using VW 506.01 stuff in an engine equipped with a diesel particle filter and/or advanced three way catalyst.

TS