I'm getting ready to change the fluid in my 300d, it has 140k+, is it advisable to change to synthetic or should I just stick with the regular stuff? I know this has been covered before, just want to know if anyone has had any problems.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k