Do NOT use GM Limited Slip Additive with Mobil 1 LS 75w90
- Thread starter Robvette
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MolaKule
Staff member
It depends on the LS differential design.
Making figure 8's in a parking lot after fluid warm-up will indicate if you need additional FM.
Making figure 8's in a parking lot after fluid warm-up will indicate if you need additional FM.
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dnewton3
Staff member
This isn't new.
In fact, pretty much any major lube blender is going to tell you not to add other brand additives to their already fully formulated LS gear oils.
In fact, pretty much any major lube blender is going to tell you not to add other brand additives to their already fully formulated LS gear oils.
LS pre-mixed gear lube has IME been a little light on the LS additive. You have to drive it to test it. I usually need to add one more full bottle of additive to quiet the plates, sometimes more.
Leaving a little bit of room in the fill, then doing a drive test like what Molakule described above is the only way to get the additive mix correct. You can get the plates to audibly “pop” at low speed with a tight enough turn.
The correct additive level is not going to be found with a phone call or email.
Leaving a little bit of room in the fill, then doing a drive test like what Molakule described above is the only way to get the additive mix correct. You can get the plates to audibly “pop” at low speed with a tight enough turn.
The correct additive level is not going to be found with a phone call or email.
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Is your experience with Mobil 1 LS or another premixed?
Yes, M1. I had to add slightly more than one extra additive packs to quiet the LS in my particular truck. I tend to get about 40k out of each fill.
Next time, I just used plain 80w-90 and two complete Lubegard additive packs. Same result and a little cheaper. I have a steep uphill section in my parent’ neighborhood, with a tight, low-speed 90 degree at the top. When I notice my rear-end pop on that, I know it’s time to change the fluid and add additive.
ETA: so this is my experience with ONE particular vehicle with an LSD of two I have - you may require a little experimentation to find what works w/yours. I thought it useful to give a good example of what @MolaKule said above about testing/listening to get the additive mix correct.
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I’ve used the GM LS additive or the Ford version in many Ford 9” rear ends (with the traction-loc system) in conjunction with the Mobil 1 75w-90 LS or the Mobil 1 75w-140 LS.
Never any issues with performance or wear.
Advisable ? I don’t know. Harmful ? I don’t think so.
Never any issues with performance or wear.
Advisable ? I don’t know. Harmful ? I don’t think so.
The Mustang's LSD will groan with any LS oil (even Redline) until you add the Ford additive. Might be the same situation with GM. Listen to your differential, not the oil makers.
You can add SOME to Amsoil SG. But try it without first.
But yeah, never will you need a full dose.
But yeah, never will you need a full dose.
The basic test is to do some tight figure 8’s. If the wheels chatter then you need the additive.
Add as needed then do more figure 8’s to mix it in throughly.
Z
Add as needed then do more figure 8’s to mix it in throughly.
Z
This is the first thread that I have ever bookmarked. Very interested in reading responses.
I had an 2004 GTO that I used Mobil 1 75w140 in. The rear end in that car is a Dana unit with a Ford style clutch pack. It did take a bit of type F friction modifier to keep the noise down.
I ended up switching to Torco RGO 85w140 and using Torco's type F modifier. Being conventional it was cheaper and I changed it every 15k miles anyway. This seemed to be the favorite of the GTO crowd at that time.
I ended up switching to Torco RGO 85w140 and using Torco's type F modifier. Being conventional it was cheaper and I changed it every 15k miles anyway. This seemed to be the favorite of the GTO crowd at that time.
If it's got a zexel-torsen any motor oil or gear oil is fine.