Originally Posted By: Ramblejam
Originally Posted By: Kira
rickmeseke asked, "If the manufacturer says its good until 100k why do it a third of the way early"?
ANSWER: Because car companies are staffed by lying, filthy dogs. They lie about service intervals to keep projected maintenance cost estimates down.
Sampling the fluid at 10K intervals may reveal a stable system which can go longer than the 30K the OP mentioned.
Good luck with your Fiachrys.
Here's the word directly from the transmission manufacturer:
"ZF 5-, 6-, 8- and 9-speed as well as the ZF 4HP20 automatic transmissions are filled maintenance-free with specially developed partially synthetic ATF oils. Maintenance-free fills are intended for normal operating conditions. Especially driving at very high operating temperatures can result in accelerated aging or increased wear of ATF oils. It is recommended, in the event of severe operating conditions, such as:
- frequent highway driving in top speed range,
- offensive, sporty driving style,
- frequent trailer operation,
being above average, oil purification (oil change) on automatic transmissions is recommended between 80,000 km and 120,000 km, or 8 years, depending on the load. In each case, only released ATF oil may be used for oil changes. And oil changes must be performed in accordance with the relevant specifications."
AND, the above in bolded-italics is their CYA out.
If you intend to keep your vehicle for some time, I would advise changing fluids according to their Severe Service Schedule (SSS).
In lieu of no clearly defined SSS, use an oCI of 1/3 the Lifetime Fill schedule.