All Mobil 1 products are synthetic, the 2003 specs call for Mercon ATF (a dino oil) in the tranny, and synthetic (or conventional, because it really doesn't matter) in the rear-end--this from the owner's manual:



Tremec recommends Mobil1 ATF for the 3650 (from the 3650 service manual):



The absolute truth is that is doesn't matter, any ATF meeting the Mercon specs, and any gear oil meeting the API specs of the Motorcraft gear oils will work fine.

People spend far too much time fretting and haranguing over what brands of lubricants to use; this includes engine oils. It is much more important to select lubricants with proper composition and characteristics (I.e. the recommended lubes, or those meeting the same specs), and keep the lube fresh and clean, than to worry over what base stock was used and who bottled it...

 

Thanks for the info, it doesn't say in my owners manual how offen to change the oil in my engine and trans. Have anything on that?[IMG]17461524121_286730760_IM1_02_565x421_A_562x421[/IMG]

 

2003 Maintenance Schedule...

Ford says the engine oil should be changed every 5000 miles, or 6 months, whichever occurs first for normal duty operation. 3000 miles or 3 months for special operating conditions--I do the latter.

The manual transmission change interval is specified as "as required", I say no less than every 50k miles. The rear axle spec is every 150k miles, I would not go more then half that between changes...