I haven't read the 229.5 spec, so I don't know what it says. I suspect it specifies certain characteristics needed for long drain intervals. You might be fine running the Hyundai stuff and changing it more frequently, however this is in the realm of experimentation. If you're willing to take the chance of experimenting on your engine, I for one would be interested to see what happens.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.