Redline D4 or D6 in my Focus?

[Klutch9]

After seeing the improvement the Redline D6 made in the 6F35 unit in our Fusion, I've decided to do yearly drain/fills with Redline products in both of our cars. For the Fusion, it's D6 all the way. For the Focus though, which recommends Mercon V, the D4 fluid matches up most closely. However, the 08-11 Focus, while mechanically identical to my 07, recommends Mercon LV instead of the Mercon V my Focus does. I never understood why the 05-07 Focus wasn't 'upgraded' to the LV spec, since the automatic trans units used in 05-11 were all exactly the same

So, simply put... Mercon V = use D4, Mercon LV = use D6. I'm debating which one I should use though. The D6 is all-in-all a higher quality fluid than the D4, and is slightly more shear stable. The operating viscosity of the D4 is 7.5 (as is Mercon V), whereas the D6 is 6.1 (as is Mercon LV). I have used Maxlife ATF in the Focus before, the newer formulation, which also has a 6.1 operating temp viscosity. So I'm sure the D6 would still do very well, I'm just wondering if it'd do better than the D4. Any thoughts? Thinner fluid in the cold will make for better shifts, too. At least I think it will...

 

[randomhero439]

Personally I would just use what its specced for, which is D4. Im sure D6 would be just fine though. If it was never "upgraded" to the LV spec, there is probably a reason why.

 

[GearheadTool]

I put some D4 in my 2000 Volvo. Seems to work well.

 

[bigjl]

It was explained to me that a conventional automatic needs to be thought of as a large pump.

So pressure is, i would think, important.

LIke if you used a thinner fluid would that not mean the gearbox could be sluggish, thinner meaning less pressure compared to same circumstances with a thicker fluid?

Similar to when an autobox is really low on fluid?

Just throwing ideas out there, I take my Autos to a specialist as even though I have had be sump of a few and swapped gearboxes and torque converters when I ran a garage I was little more than the mechanics helper.

I always enjoyed having a poke around though.

Amazing bits of engineering autoboxes.

 

[GearheadTool]

Originally Posted By: bigjl
It was explained to me that a conventional automatic needs to be thought of as a large pump.

So pressure is, i would think, important.

LIke if you used a thinner fluid would that not mean the gearbox could be sluggish, thinner meaning less pressure compared to same circumstances with a thicker fluid?

Similar to when an autobox is really low on fluid?

Just throwing ideas out there, I take my Autos to a specialist as even though I have had be sump of a few and swapped gearboxes and torque converters when I ran a garage I was little more than the mechanics helper.

I always enjoyed having a poke around though.

Amazing bits of engineering autoboxes.


I have wondered the same!

Wouldn't the thinner fluid give more lubricity of the autobox when it is icy cold out, and as long as it could maintain strength it would be OK when it is 105 out?

 

[chad8]

Originally Posted By: GearheadTool
Originally Posted By: bigjl
It was explained to me that a conventional automatic needs to be thought of as a large pump.

So pressure is, i would think, important.

LIke if you used a thinner fluid would that not mean the gearbox could be sluggish, thinner meaning less pressure compared to same circumstances with a thicker fluid?

Similar to when an autobox is really low on fluid?

Just throwing ideas out there, I take my Autos to a specialist as even though I have had be sump of a few and swapped gearboxes and torque converters when I ran a garage I was little more than the mechanics helper.

I always enjoyed having a poke around though.

Amazing bits of engineering autoboxes.


I have wondered the same!

Wouldn't the thinner fluid give more lubricity of the autobox when it is icy cold out, and as long as it could maintain strength it would be OK when it is 105 out?


Exactly WRONG . In this year transmission you need the higher fluid pressure to keep parts lubricated. Use the older spec fluid that it calls for.

 

[pbm]

I believe I read somewhere on Redline's site that D4 and D6 are identical except for viscosity....maybe you could mix them...sort of D5...JK.

PS: I think 'yearly D&R's" with a quality syn ATF is overkill unless you have a known problem A/T.

 

[bmwtechguy]

If you keep a quality fluid like Redline ATF clean, you can safely keep it in service for a much longer time. Think inline filter like Magnefine. Yearly drain and refills would be costly and way overkill in most situations with this fluid. I think either fluid will work fine with the older car. You being in MN certainly would not hurt to have the 6.0 cst fluid when cold. GM back-specs their thinner Dex6. Maxlife recommends it for MercV. If in the unlikely event it shifts strangely, you can always switch it back next time.

Higher pressure? The pump/transmission has an ECM-controlled fluid pressure regulator to keep pressure where it needs to be, based on system demand. So low pressure should only be an issue with a very worn transmission that has aquired excessive internal leaks that would lower pressure overall and lower lube oil volume. That is when you could possibly benefit from a thicker fluid or if fluid temp gets very high. Do you build these units and know the specific failure modes, or possibly had a bad experience using one of the thinner fluids?

 

[Trav]

I use ML and Amsoil fluids but if you look at Amsoils site their version of D6 is called fuel efficient fluid.

I have used both in my GTP (4T65E-HD) Subaru, Ford 4R100, Infiniti M35X and a few others that i drive on a regular basis and the only conclusion i came to is cold performance (0-single digits ) is improved with the D6.

D6 shifts faster cold where the D4 tends to hold gears a little longer and shift are slightly firmer for the first few minutes. Nothing severe.
This also has a lot to do with how the unit deals with the higher cold pressures of the D4.

In GM cars i really like the ML or the D6 but the rest i use the "normal" D4, shifting hot seems better and TC lock and unlock seems smoother with the D4.
Keep in mind all my units with the exception of the GM (which is back spec'd to D6) use D4 as the OEM spec.

Longevity doesn't seem to be an issue with the D6 in comparison to the D4.
The quality of both is identical when your taking full synthetics like RL and Amsoil, even ML is a full synthetic.
Its the synthetic that makes D6 in your words "D6 is all-in-all a higher quality fluid than the D4", it really isn't with these fluids. The OCI for both is 50K severe service on Amsoils spec sheets.

If the units is in fact identical to the previous years (i have no idea if the operating pressure is the same or not) then use the D4.


I used D4 and D6 instead of Amsoils descriptions just to keep it simple.

 

[bigjl]

I use Morris MPC in my Taxi autobox.

Meets the important Chrysler +3/+4 spec.

I don't know what autobox is in there as London Taxis are a bit of a parts bin special, I do know it is a Chrysler one though, perhaps from the Voyager minivan or Jeep Liberty/Cherokee?

 

[Hokiefyd]

Originally Posted By: bigjl
I don't know what autobox is in there as London Taxis are a bit of a parts bin special, I do know it is a Chrysler one though, perhaps from the Voyager minivan or Jeep Liberty/Cherokee?


If it's a FWD powertrain, it may be Chrysler's 41TE from the minivan. If it's a RWD powertrain, it may be Chrysler's 42RLE from the Jeep Liberty. They are somewhat related to each other, both being part of Chrysler's "Ultradrive" transmission family.

 

[martinq]

Both Red Line fluids are shear-stable (D4=7cSt, D6=6cSt) but for some reason D4 has a higher VI. Despite that my vote would be for D6 as D4 is heavier than necessary for street driving in N.A..

That aside, I would also consider Mobil 1 ATF (similar to D4, might be easier to get) or Valvoline MaxLife (economy option).

IMPORTANT NOTE - ANY of these fluids are vastly superior to the sheared 4.x - 5.x cSt that we see in Dexron III / Mercon fluids of old. You do NOT need a 7.x cSt fluid for a Dexron III application.

 

[Klutch9]

Well, I decided to stick with the fluid that most closely matches the Mercon V, and ordered some D4 for my Focus. Having just done a drain/fill about 6 weeks ago with some Valvoline Mercon V, I'm going to do another drain/fill with the D4 in springtime, and then I think I'll be good for quite some time. I'm thinking yearly drain/fills with the Redline might be a little overkill, so maybe I'll do every 2 years or every year and a half. Still gonna do the D6 yearly in the Fusion, since it has a problematic transmission.

After the upcoming drain/fill in the Focus (which will be the 3rd I've done), that will be a total of 9 qts exchanged, with a 7 qt sump. Almost all of the fluid should be pretty fresh then. I do know there was some front end work done to my car before I bought it, so I'm not sure if the tranny cooler was ever replaced. If so, some fluid may have been exchanged then. But I'll assume there wasn't. Ford recommends 30,000 mile drain intervals for severe driving, 60,000 for normal driving. Before I bought my car, it was previously owned by someone who lived in Brooklyn, so I'm guessing those 21,000 miles on the car were quite hard.