I've been reluctant to switch to synthetic ATF in either my SDL or my 300D because of cautions people have raised about the potential adverse effects in swithcing from dino to synth in high mileage cars. I use synthetic engine oil (Delvac 1), but I just can't seem to pull the trigger when it comes to the tranny. If I ever had to reseal or rebuild one, then I would switch to Mobil 1.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 160k miles
06 E320 CDI "Rutherford", Black on Tan, 180k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 79k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife