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Idk whether or not to put dot 3 or dot 4 in my 2012 3.7 v6. The brake/clutch fluid is low and my clutch seems like it won't disengage so my car won't go anywhere... any suggestions or diagnoses??
 

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My 2014 uses DOT 4 fluid in the clutch/brake system. It says so specifically in my 2014 owner's manual. I would assume then that back to the 2011 or at least the 2013 use DOT 4 as well. Strangely, if you look at aftermarket reservoir caps for the 2011-14 Mustang they all say DOT 3 on them. I can't view what my original 2014 cap actually says at the moment but I'd go with the better fluid stated in the manual. You can mix DOT 3 and 4 but not DOT 5.
I wonder if the number crunchers at Ford decided to not bother to update the cap to say DOT 4 on it to save a few pennies. The 2009-14 Mustang use the same reservoir 9R3Z-2K478-B but I don't know when Ford actually switched over to DOT 4 from 3 in the Mustang. Maybe someone on here can post what their 2011, 2012, and 2013 manuals say in the capacities section and verify my suspicions about the mislabeled reservoir caps.
 

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DOT3 is the minimum spec for the 2014 but DOT4 is also listed as recommended. My ’14 cap calls for DOT3.

The 2014 owners manual says the following…
EDCA08D2-6597-48BE-B330-A26CABF760A7.jpeg
 
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I kinda like the Castrol synthetic DOT3/4 fluid, because it makes this DOT3 or DOT4 question a non-issue
 

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oops, my bad, just went to look at the can, it's Valvoline not Castrol . . . I don't think it is a blend; it says it is ". . . compatible with all braking systems requiring DOT3 or DOT4 . . . "

it also has a relatively high boiling point, not as high as a true race fluid, but higher than plain old DOT3 (dry boiling pont 430 F, minimum wet 311 F)
 

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That sounds like it's a blend to me. I like the idea of it. It's like a DOT 3.5 basically.
I'm guessing that it's just DOT 4. Since DOT 4 can be mixed with DOT 3, it is legal to state that the DOT 4 fluid is compatible with braking systems requiring DOT 3 or DOT 4. It's sort of like the way that ALL squares are rectangles but not all rectangles are squares. You can use DOT 4 fluid in all brake systems requiring DOT 3 or DOT 4 fluid, but you can't use DOT 3 fluid in a DOT 4 required system. The newer Mustangs require DOT 4 because of the more robust brake systems used on them which requires a higher temperature fluid. My car has the typical 4 piston front calipers but the Shelbys and some PP packages have the 6 piston calipers. That's some massive stopping power up front!
 

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That's a good point. DOT 4 is backwards compatible but DOT 3 is not forward compatible. If it was a lesser performing fluid then it wouldn't be ok for DOT 4.
I'm curious if the Brembo package on my car is why my owner's manual specifies to use DOT 4 but crjackson's manual says DOT 4 recommended and he's got the Brembo. I figured that my manual was a later mid year publication but it's dated June 2013 so it's more likely a first printing for the 2014 car. I'm going to look at my cap later today. I'm betting that Ford was just inconsistent with their publications for the 2014.
 

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Probably a documentation issue. My car was manufactured in late 2014 and it’s a Track-Pack car with Brembo. Puzzling somewhat. My brake reservoir cap says DOT3.
 
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Just go with the DOT 4. It's compatible with your system (and any residual fluid if it happens to be DOT 3), has lower moisture absorption and a higher boiling point than DOT 3. When it doubt go with the higher spec fluid as long as it's compatible. Having said that your clutch issue sounds like there could be more to it than just fluid level. If a flush and refill doesn't fix it you may have a bad master or slave cylinder issue.
 

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I checked and my cap also says DOT 3. I'm wondering if Ford started using DOT 4 at some point but just never updated the reservoir cap to save $ on a new mold and catalog listing. I don't know if there's any way to tell other than looking in the Ford shop manual for a 2014/13/12/11.
 

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I'm thinking the simple practical solution is to buy the DOT3/4 stuff; and then don't worry about it any more
 
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