Is 85w140 too thick for single digit temps?

Status
Not open for further replies.
Joined
Sep 10, 2018
Messages
228
Location
Northern va
Hi all, long time lurker first time poster. I have learned a lot from this forum and searched quite a bit but didn't find exactly what I was looking for so it's time to ask the experts!!

I have a 2013 F150 ecoboost that originally came with an open 3.31 rear. I eventually ditched the stock wheels and tires and put some 35" Nitto Trail Grapplers which absolutely killed the power in the truck. I then swapped to 4.56 gears and added a Detroit true trac in the rear. I know Eaton recommends a mineral based oil but allows a synthetic preferably without friction modifiers.

The place I had the rears done absolutely recommended a mineral oil and never a synthetic. I did the break in for 500 miles with Mobilube HD 85w140. Dumped it and refilled with the same. It's been in there now for about 20k miles. No problems or weird noises.

Just for kicks I took some of the Mobil 85w140 and put it in the freezer overnight in a solo cup. It had nearly turned solid!! I turned the cup upside down and it didn't flow at all. The freezer temp is set to zero degrees. I did the same test with Mobil 1 75w140 I had laying around and it was thick but still very fluid like.

So long story short, For my climate where in the winter it can get to the low teens/ single digits is this a problem? When I leave my neighborhood it's a quarter mile to the highway then it's 65-70 mph. Can this actually cause damage? How long does it take gear oil to thin out? I'd really like to stay with a mineral oil if possible. Would an 80w90 be adequate or too thin for the 4.56s ? I don't tow much but for what's its worth in the summer the diff gets really hot to the touch!

One thing I've noticed is that Lucas 85w140 seems to have a really low pour point. Almost to the point that it seems like it's a mis print at -27f. The Mobil is supposedly good down to 0 but it didn't flow at all in the cup.


Thoughts? Am I overthinking this? If the Lucas does really flow that much better I may try it.

Thanks in advance!!
 
I've never tried it. I have used 80w90, 75w90 and 75w140 without any problems in any weather I've seen throughout Michigan. My winter or year round daily drivers typically get a 75wX synthetic. Mustang has 85w140 but its a weekend/summer car.
 
Any specified lube will be fine. We survive up here.
wink.gif
 
I run Co-op SL 75w140 gear oil in my Ram 3500 and previous Ram 1500. The 1500 ran through several cold winters up here and it performed fine. I inspected the gear set at one point and it looked pristine. This oi is a full synthetic group 4 oil. Pour point is -42C with viscosity of 244cSt at 40C. Its a thick oil that performs well. The conventional based 85w140 has a pour point -24C with viscosity of 337cSt at 40C. While both are 140 weight, the conventional version is considerably thicker when colder.

my plan of attack is to slowly drive away during extreme cold. Just take your time.
 
If it is I'm screwed, the Mobil 1 version of it is in the rear differentials of all three of my vehicles.
 
my 2011 nissan SV came with nissan-dana 44 + used cheap 75-140 OE mineral lube, i got an aluminum spicer-dana cover used on the titan + literature with the cover said 75-90 SYNTHETIC as does the Dana site, heavier lube recommended for severe use. i put in Redlines top of line Ester based 75-90, they have 75-110 + 75-140. can't believe any shop today don't know the SUPERIORITY of real SYNTHETIC lubricants!!
 
Was your work done by EAST COAST GEAR in Raleigh NC?

I had my rear done there and they absolutely did not want synthetic in the diff. They also told me to use 85-140 which i am. They push the lucas which i don't use. I have valvoline dino in mine.

If the level is correct i don't think it is too thick unless you are in Alaska.
 
Last edited:
No, any 85W140 would not cause damage to the differentials in the circumstances.
Differential oil is not too thick at temperatures above it's pour point ......Mobilube's 85W140 being -18*C.

Quote
the diff gets really hot to the touch

..... that's an indication to consider adopting a thicker gear oil in higher KV @40*C .

Agree with you that -27F pour point for Lucas 85W140 is a misprint.
Having said that, it will work well in your differential.

Do consider BrianF's approach ..... in slow and steady starting moves from stationary , first thing in a cold winter morning.

Originally Posted by BrianF
my plan of attack is to slowly drive away during extreme cold. Just take your time.
 
Last edited:
Thanks for all the replies! No the work wasn't done by easy coast gear, but I did read their recommendation on pushing Lucas gear oil. I typically don't use Lucas anything but I thought the super low pour point was interesting.

The shop I had the work done only recommended mineral oil ( no specific brand) because of the true trac. They didn't seem to care much about the fact that you * could* use a synthetic. They said it just works better with a mineral oil. They install tons of these things, so I took their word on it

Going by the fact that they call for a 140 wt from the factory I figured that a 90wt would be too thin? But if not I wouldn't have a problem running an 80w90 either. I thought the 4.56s and those super heavy tires might require a 140wt.

Another option other than the redline NS oil, we also stock Mobil delvac 80w140 synthetic. It's what we use in all of our dump truck rears at work. Plus it's free so I guess I could try it. The specs say it's quite a bit thicker but has a nice pour point also. The only reason I didn't use it from the get go is cause it's a synthetic. We also keep barrels of the mobilube hd 85w140 and 80w90 for the Volvo A30d trucks we have which hold like 6 gallons in each rear !!

I may pickup a bottle of the Lucas 85w140 and do the freezer test. At 0° it should be somewhat fluid like if it does in fact have a -27 pour point.

Thanks again for the replies !
 
85W140s are virtually a monograde (good IMO), but single digit Fs I'm not comfortable with.

When you look at the oil loop in a differential, you do want it to move early. And unfortunately the pour point only tells you how easy it is to change in that temperature, not how well it moves around.



There's some general engineering formulae for viscosity requirements at mean pitch line velocities for different gear patterns...we can work with that a bit maybe to make some recommendations.

How hot is hot to the touch ?

If you can hold your hand on it for 5 seconds, it's around 70C, which is not really THAT hot.

BTW, I used Royal Purple 75W140 in my Nissan (turbodiesel Navara, with 4.11 from the factory), and it turned to gluggy black junk inside a year (no water crossings)
 
I saw that video before and was wondering if my rear looked like in those temps. I may just change it out with the synthetic 80w140 delvac that I have at work before it gets real cold out. I know that's a heavy duty oil with no friction modifiers

I'm not sure how hot it actually gets. I guess I could borrow an IR gun and see. The last time I touched it, there was no way I keep my hand on it more than a second or 2. But I had just came off the highway and it was like 95 degrees out that day.
 
Correction, I might not be screwed. I just checked my log, I have Mobil 1 75W140 in the rear differentials.
 
There is a reason that they don't want a syn oil in the rear end. Just because marketing tells you something does not mean it is true. Its called marketing for a reason. It means you take your weaknesses in your product and push it as your strengths. Are syn oils better. Maybe but by how much. A mile or an inch. In real world conditions it might be only a hair. Oh and if that dino oil you have for dump trucks makes them live in cold weather I bet your pickup will be just fine with it in the rear.
 
The Dino gear oil we have is strictly for the off road dump trucks. Never any problems. I've seen the rears opened up ( usually to be resealed) and they always look spotless. Same goes for the wheel hubs.

We always run the synthetic in the on road dump trucks. They almost never get opened up unless an axle breaks. They typically never get serviced otherwise.

I think I'll just stick with the dino 85w140. Seems like most of aftermarket ring and pinion companies tend to recommend it
 
Status
Not open for further replies.
Back
Top