Will my old gearbox oil react with my new gearbox oil.

[Siye_MeganeRS]

So i have an Megane MK4 R.S. Trophy with the manual PK4 gearbox and torsen LSD.

The oil currently in the gearbox is Elf Tranself NFX 75W80. (OEM stuff)

I have bought and would like to change it to Millers CRX LS 75W90 Nanodrive NT+ as it offers more protection and is recommended by a company called KTEC who specialise in Renault Sport stuff.

So my question is with both the oil being different weight, viscosity and brand... when i go to change the oil... some of the old stuff is going to be left in the gearbox right?

I know these oils have additives due to the LSD part of the oil. How likely am i to run into issues with the oils reacting with one another and messing stuff up. I have already had the bearings changed in this gearbox... I want the better oil in.. How do i proceed without potentially messing anything up? Or am i ok to just change it normally?

Elf data sheet - https://cdn.opieoils.co.uk/pdfs/elf/TRANSELF-NFX-SAE-75W.pdf

Millers data sheet- https://cdn.opieoils.co.uk/pdfs/millersoils/MOTORSPORT-CRX-LS-75w90.pdf

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[SubieRubyRoo]

HPL makes a differential cleaner. If I were as concerned as you are, I’d drain the diff(s), fill them with the HPL diff cleaner, drive the car awhile (from maybe 20 miles to a few days), then drain & fill with the Miller’s.

BTW that Millers stuff does look really nice… if it was available here and we didn’t have HPL, the Millers Nanodrive stuff would definitely be in the top 3 choices!

 

[Greasymechtech]

No reaction to worry about

Drain/refill and keep driving. Repeat as needed for regular maintenance.

 

[Siye_MeganeRS]

No reaction to worry about

Drain/refill and keep driving. Repeat as needed for regular maintenance.

So 100 percent if i drain as much of the old stuff out as i can through the drain plug.... and refill with the millers ill be all good?

The ELF says its for GL4 application and the millers says both GL4 & GL5. Just want to proceed with caution as iv already had this trans rebuild.

Thank you

 

[SubieRubyRoo]

HPL makes a differential cleaner. If I were as concerned as you are, I’d drain the diff(s), fill them with the HPL diff cleaner, drive the car awhile (from maybe 20 miles to a few days), then drain & fill with the Miller’s.

BTW that Millers stuff does look really nice… if it was available here and we didn’t have HPL, the Millers Nanodrive stuff would definitely be in the top 3 choices!

Differential Life Cleaner 80W-90

HPL Differential Cleaner is designed for those who wish to clean deposits in their differentials left behind from commodity-type lubricants that are designed to “meet the spec.” Differential Cleaner is specially formulated and fortified with ester providing safe cleaning in the differential...

www.advlubrication.com

 

[SubieRubyRoo]

So 100 percent if i drain as much of the old stuff out as i can through the drain plug.... and refill with the millers ill be all good?

The ELF says its for GL4 application and the millers says both GL4 & GL5. Just want to proceed with caution as iv already had this trans rebuild.

Thank you

Yes, gear oils that don’t use sulfur as an EP additive will sometimes be rated both GL4 and GL5. You say the Millers is rated like this, and Motul Gear 300 and the HPL Differential Life fluids are some others. I don’t know the whole list but Millers seems to be top-shelf!