Gear Oil Upgrade For Towing

[1Seekingzen]

I tow my 3500 lb tear drop on average 6000 miles a year, Seattle to Arizona, Alaska, Montana, etc. I read that if you tow frequently, you should switch to 75w-140 gear oil to prevent oil thinning. Has anyone doe this, and how badly does it hurt gas mileage, if at all? What brand of oil did you use? This is for my 2024 Gladiator Mojave

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[Hootbro]

Plenty of people have switched to 75W-140 to include myself. Honestly, I track my mileage in my signature Fuelly links below and really could not tell you any discernable hit in mileage. I am sure there is some but it is probably in the tenths of a MPG if at all.

Any brand rated for GL-5 will do you fine and just pick whatever brand you have experience with. I have used Valvoline, Amsoil, Mobil and even Supertech over the years. Everybody has their favorite sauce.

 

[whysoserious]

I run 75W-140. I don't tow. But if it's good enough for Dana, It's good enough for me. I've run the Mopar spec and Dana's and like @Hootbro said, no noticeable difference in mileage.

 

[ShadowsPapa]

Plenty of people have switched to 75W-140 to include myself. Honestly, I track my mileage in my signature Fuelly links below and really could not tell you any discernable hit in mileage. I am sure there is some but it is probably in the tenths of a MPG if at all.

Any brand rated for GL-5 will do you fine and just pick whatever brand you have experience with. I have used Valvoline, Amsoil, Mobil and even Supertech over the years. Everybody has their favorite sauce.

As reflected in the many threads on the topic.

I've run the Mopar spec and Dana's

A lot of people like the "bagged" Valvoline.

Little waste, simple to use.

 

[TheSolarWizard]

I see zero reason at all to run synthetic
I beat the piss out of my jeep and run Lucas 75-140 with excellent results

 

[ShadowsPapa]

I see zero reason at all to run synthetic

Is there a reason not to?

 

[TheSolarWizard]

Is there a reason not to?

No just seemed like everything listed was a synthetic so far

 

[ShadowsPapa]

I run synthetic gear lube in things because it has better resistance to viscosity changes with heat, handles heat better and is more resistant to oxidation. It holds up better under stress and heat - lasts longer before breaking down.
If you get into water a lot, synthetic would be better as it sheds the water more easily - doesn't emulsify easily.

But if you change often enough, you probably won't know the difference. So for many it won't matter a bit. Depends on your use and how often you tend to clean things out and start fresh, I guess.

 

[RudeJeepin]

A lot of people like the "bagged" Valvoline.

Little waste, simple to use.

And it's got the "V" for victory.

 

[ShadowsPapa]

I believe the owners manual states synthetic is required, at least in my 2024.

My 2025 manual doesn't mention it at all for the axle differentials. Just the specs.
For me, it's about the heat handling capability and ............ 'why not'...............

 

[Hootbro]

A lot of people like the "bagged" Valvoline.

Whoever came up with the idea of bagged gear oil and implemented it, needs a Nobel Prize.

 

[RudeJeepin]

My 2025 manual doesn't mention it at all for the axle differentials. Just the specs.
For me, it's about the heat handling capability and ............ 'why not'...............

I remember watching something on TV, maybe motor trend magazine or one of those shows.
Anyways, they installed a temp gauge on rear axle. Did test loop measuring temps with conventional axle oil. Then switched to full synthetic, same weight, and did test loop measuring temps again.
The full synthetic showed measurable difference in lower temps.
I believe it was the same test they also measured fuel economy. Seems like there was a slight gain, but not much. Maybe over a year it would add up to something.
The lower temps would be enough for me to use it. Especially since the is some belief that temps play a part in the rear axle life of my Rubicon.

 

[Wheelin98TJ]

Is there a reason not to?

Currie says non-synthetic clings better.

https://www.currieenterprises.com/w..._1AHo3veqx6YO1SkkI44WYZq2j8l2hCInWuyOAENwpz2m

 

[jac04]

I use Valvoline synthetic in my JT Mojave.

ECGS built me a HD Dana 44 rear axle for my JK Rubicon. It came with a 5-year warranty as long as I used Lucas 85W-140 conventional gear oil.

Here is what they say about gear oil selection:
https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf

 

[Wheelin98TJ]

I use Valvoline synthetic in my JT Mojave.

ECGS built me a HD Dana 44 rear axle for my JK Rubicon. It came with a 5-year warranty as long as I used Lucas 85W-140 conventional gear oil.

Here is what they say about gear oil selection:
https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf

I wonder if ECGS did their own testing.

Currie found the same thing. Cooler oil and housing with synthetic, but hotter gears.

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