Synthetic GL-5 and MoS2

[Falcon_LS]

I'm going to be servicing the differentials on my Montero, and previously used Motorcraft Premium Rear Axle Lubricant 80W-90 without any additives. At one point, I used Lubri-Matic GL-5 80W-90 when I couldn't source the Motorcraft.

When I went to do my shopping this afternoon, I got a great deal on Mopar's 75W-140 full synthetic GL-5. The price difference between Mopar 75W-140 and Motorcraft 80W-90 was $2.50 a quart, and for $7.75 a quart for full synthetic, I figured I couldn't go wrong. Motorcraft's 75W-140 was going for $26 a quart, so it makes me wonder why the Mopar stuff (Shell?) is much cheaper (both products manufactured in October 2010).

Anyhow, the plan was to initially run Motorcraft 80W-90 and add the recommended dose (20 ml per liter) of Liqui-Moly MoS2 Differential Additive. It made quite a difference in my Grand Marquis (with Motorcraft 80W-90), and there was also a small improvement in fuel economy (0.3 km/L or 0.7 MPG).

But with the synthetic gear lube, will I benefit as much from the MoS2? I'm not just looking at it from a fuel economy point of view, but from a protection point of view as well. With the summer temperatures here, I figure the added protection (if any) is worth paying for. Thanks!

 

[Audi Junkie]

I would not use it.

 

[unDummy]

I would definitely use it in the rear-end, front-end... I find that moly benefits gearboxes regardless of the gear oil used.

 

[mechtech2]

With no manual trans synchros to worry about, the moly sounds like a great idea.
Don't go crazy with your dosage.

 

[dailydriver]

I would not use MOS2 in a limited slip differential (at least a clutch/cone type).

I'm not sure if you have a LSD in the Montero.

 

[Falcon_LS]

Thans for all the input!

I haven't got an LSD, which is why I was considering it. I'll go with the recommended dose (20 ml/1L), so I'll need 3 tubes for the rear diff and 2 for the front.

 

[Falcon_LS]

Response I have received from the R&D Manager at Liqui-Moly regarding the use of MoS2 Gear Additive with synthetic axle lubricants:

Quote:
There is no problem to use MoS2 gear oil additiv also in group III/IV Oils with the same benefit as in mineral oils. The function of MoS2 is to reduce the pitting building at the metal surface.