[modern] So you want to know about Shell Spirax do you?

Hows this to start?

I quote:

SPIRAX Family Performance Data

4.5.3   SPIRAX AX & GX

d) Supplementary Performance Data - SPIRAX GX (continued)

e) Promotional Data

1) Summary

SPIRAX AX 80W90 and GX 80W, the new Group premium-tier gear oils  

based on Lubad 752 have been designed to meet the most
demanding OEM requirements for axles and manual synchronised
gearboxes respectively. These oils meet the targets of the new
MAN specifications for axle oils (MAN 342 (EOD)) and manual gearbox
oils (MAN 341 (EOD)) which are targeted at extended oil
drain recommendations, and the new MB specifications MB 235.6 and
MB 235.5 respectively. These new specifications should be
issued by end 1996 and where relevant, finalised by 1Q 1997.

In addition, to support of the launch of the new range of premium  

tier gear oils, SPIRAX AX 80W90 and GX 80W have also been
assessed in comparative product differentiation studies with
mainstream counterparts currently approved by MAN and Mercedes
Benz ie SPIRAX MB 90 and MA 80W containing Lubad 166 (Anglamol 99).
Only two packages, based on Anglamol 99 from Lubrizol
and Mobilad G210 from Mobil Chemicals, are approved by Mercedes
Benz for Sheets 235.0 and 235.1. All competitors� lubricants
approved by Mercedes Benz contain one of these additives and the
differences in performance of the gear oils lie only in the base
oils and the pour-point depressant used. Therefore this study
provides fundamental data on competitor products as well as Group
gear oils.

The following characteristics of the oils were compared; fuel  

economy benefits, deposit-forming tendency due to thermal
decomposition in thermal oxidation stability tests, wear protection
and extreme-pressure performance after ageing (CEC oxidation
test). In this limited set of tests it was demonstrated that the
following benefits will result from the use of the new technology:

    Protection against wear:

    SPIRAX AX & GX showed better reserve in performance after  

ageing (up to temperatures of 135�C in the CEC test) than

    Extreme-pressure performance:

    SPIRAX AX & GX gave the same level of extreme-pressure  

protection under boundary lubrication conditions, as SPIRAX MB
& MA.

    Oxidation stability:

    SPIRAX AX & GX were found to be far better than SPIRAX MB & MA  

in terms of resistance to oxidation when tested at 135�C.
They produced lower levels of deposits and suspended insolubles
than SPIRAX MB & MA to the extent that SPIRAX GX did
not give any deposits at all. The new SPIRAX oils could not be
differentiated from their commercial counterparts when tested at
120�C. This confirms the higher temperature capabilities of

    Mineral gear oils, based on Lubad 752 and 166, are not suitable  

for applications in which the temperature reaches 150�C for
long periods of time.

    SPIRAX AX & GX show a net gain in thermal stability and in  

resistance to deposit formation (modified panel coker test)
equating to a 10 to 15�C temperature drop in the oxidation test
when compared with SPIRAX MB & MA.

    SPIRAX AX & GX showed better thermal and oxidative stability  

than SPIRAX MB & MA. As a consequence of the lower
depletion rate of the additive they offer a better performance
reserve and the potential to extend drain periods.

    API GL-4 (gearbox) oils are more stable than API GL-5 (axle)  

oils up to 135�C. API GL-4 oils do not give any deposits in the
oxidation test at 120�C contrary to API GL-5 oils. This result
demonstrates why API GL-5 oils are not to be recommended in
synchromesh gearboxes.

    Fuel Economy

    SPIRAX AX & GX gave a 1.5% improvement in fuel economy when  

compared with SPIRAX HD & EP under realistic driving
conditions in chassis dynamometer test.


There’s more where that came from if you really want to know more.

XJ40 (don’t know whats in the diff but it don’t make any noise)