I keep coming across conflicting information on this.

looking at Mobile 1 "LS" synthetic gear lubricant, 75W90
Meets API Service GL-5

right stuff for a C5? does this need Limited slip additive added to it? I've found some that say yes and some that say no. the LS could mean that its already got additive in it, and it does say for limited slip applications, but it doesn't say for certain that its for limited slip differentials without any added LSD additive. can anyone who knows for sure let me know please!

my C5 has been making some noise in the rear while turning. not sure if its the diff but I suspect. I don't even know if the sound is normal or not, or anything to worry about or not. but I decided I might as well change the fluid and just see. I went to confirm the weight that I need and found some posts saying that this stuff has the limited slip additive in it already. I'm pretty sure this is the same stuff I used last time, and I DID put the 4oz of additive in it. did I do something bad to my car? I also saw a reference to needing to change this fluid every 7000 miles, but that sounds too frequent to me. looking for info from those who know!

 

I used Mobile 1 "LS" as you have posted 20k+ miles with no issue and I did NOT put in the additive. However, it doesn't hurt anything to add the 4 oz additive even with the LS lube.

If you go by the service manual, it will tell you to use Drexon LS Gear Oil 75W-90 (GM 88862624), no additive. If you have doubt, put the additive in.

 

I would recommend using Drexon LS Gear Oil 75W-90 (GM 88862624) for the Differential.

Why try to outsmart the GM Engineers?

 

that's a good question. when I was ready to change the gear oil the first time the forum happened to have a couple of different threads going about gear oil. almost everyone in those threads said use the mobil 1 or the royal purple synchromax or the amsoil. I don't think a Dextron fluid was recommended in any of them. honestly I didn't look it up myself, I sort of thought it was the factory fill. just because that's what the engine says doesn't mean anything for the diff I know, but I just went with what everyone recommended. I've heard that the Dextron gear oil is very expensive, like 3x what mobil one costs. who carries the dextron anyway? haven't seen it in parts stores, is that a dealer only item?

 

You should be fine with the Mobil 1 gear lub. All gear lubs that are rated GL-5 are listed as being compatible with Limited Slip differentials. However, this does not necessarily mean that they have the additive in the Lub. You did the right thing by adding the GM additive.

When I changed my gear lub, I used the GM synthetic lub and additive. I actually had to argue with the GM dealer because he was convinced that I didn't need the additive. I asked him where he got his information since the GM manual says that I need it. He just looked at me and said that he knows from experience.........lol.

 

http://www.mobiloil.com/USA-English/..._75W-90LS.aspx

Mobil 1 Synthetic Gear Lube LS 75W-90 is a supreme performance, synthetic, multi-purpose, SAE 75W-90 automotive gear lubricant designed to meet the highest level of performance requirements of modern passenger vehicles in all types of operating conditions, including limited slip applications, as well as delivering outstanding power transfer performance.

Compared to conventional hypoid gear lubricants, Mobil 1 Synthetic Gear Lube LS 75W-90 performs exceptionally well over a wide range of temperatures. Mobil 1 Synthetic Gear Lube LS 75W-90 achieves this through a unique proprietary formulation that delivers optimized viscosity as a function of temperature properties together with the highest level of inherent formulation stability and protects against thermal and oxidative degradation, wear and corrosion, and viscosity loss associated with premature shearing. It also can be used in extended service and for aiding in fuel economy performance.

Mobil 1 Synthetic Gear Lube LS 75W-90 contains special friction modifiers designed for limited slip-type differentials. In most applications, the addition of special LS (limited slip) additives is not required. For axles requiring the highest level of limited-slip performance, OEM specific LS additives can be added to this fluid.

 

Ahh, hate to inform you but the dealer is correct. Current online GM manual, 1997 – 2004 C5’s are to use DEXRON® LS Gear Oil. No mention of the additive. As I stated in my earlier post, if your uncomfortable not adding the additive, than add it. You just don’t need to. If you wish to check this out for yourself, see document ID 363855.

I think it is great they change the manual when something better becomes available!

 

Yes, the Dexron LS Gear Oil is expensive. I won't argue with you there but keep in mind that the Limited slip additive is already in the oil. So there is no extra cost there. I purchase the Oil from my local dealership. I am not sure if any one else stocks it.

There are many people on the forum that will tell you to use amsoil, royal purple, redline, mobile 1 and every other type of oil. To each their own I suppose...........

I choose to listen to the people who built my car

 

I'll probably get slammed,but here goes. If you want to save some money, you can purchase house brand synthetic gear lube at Walmart. If you read the specs, it will favorably compare with Mobil one. They don't make their own lube and I wouldn't be surprised if it is indeed mobil one. $4.97 a bottle vs. $20.00 a bottle for Mobil one.

 

To each their own, but IMHO there are some things it just doesn't make sense to skimp on...

 

How many pints or quarts do the rears take??
Also is there a newer tranny oil out for 6 speeds?

 

Makes perfect sense to me. Purchase a $50,000 sports car, and dump anything in the crankcase, tranny, differential, etc. What's the big deal?

 

Told you I'd get slammed.

 

The Walmart fluid is fine.... specs are specs regardless of retail source.

the LS in Mobil1 LS stands for Limited slip. It contains the additive.

 

Many Vette owners run Amsoil Severe Gear in the diff.I use it in all my cars.

Does not need to have the LS additive added,but you can if it makes you feel better.

\db2
carolina

 

thanks for the replies! I got the fluid swapped out even after discovering my old pump was no good any more. made a mess in the process. oh well!

I went to do several figure 8's like I've read is good to circulate the new fluid through all the clutch packs. I heard the sound I'm trying to defeat just for that initial right turn out of my street before getting to the parking lot. after that through the entire process everything was perfectly silent. I hope it stays that way!

I didnt' have a clanking, it wasn't like what you get if there isn't any LSD additive. I was hearing a low pitched rubbing kind of sound. I'd describe it as similar to the sound of an owl hooting except much lower in pitch, like 50-60hz. at first it was only while making a right turn while the diff was cold. then started even when I had driven it some. then I started to hear it while turning left also. figured I'd try some new fluid and see if it helps at all.

 

Just for fun:

https://www.mobiloil.com/USA-English...Corvettes.aspx


Question:
Gear Lube to Use in a Newer Corvette
Does Mobil 1 Synthetic Gear Lube LS 75W-90 meet GM spec #88862624 for Dexron LS 75W-90? Will its use in my C6 2008 Corvette void its warranty?
-- Robert Sullivan, Melbourne, FL

Answer:
No, it does not meet this spec. The GM spec product is designed with a very specific level of limited slip (LS) additive to provide optimum performance for that particular vehicle. Having said that,
Mobil 1 Synthetic Gear Lube LS 75W-90 also contains LS additive and it will provide outstanding protection and performance but it could require more LS additive for this specific application. We recommendation you follow the vehicle manufacturer’s recommendation.

 

Ok, that's just crazy talk there..............

 

What can I say??? The lawyer made them do it? Dunnoh... I'm just learning how to take off the engine covers

 

When I purchased my 4:10's from DTE they require Red Line LS and to add LSD in addition to what is already in the Red Line fluid. They will not warranty if you use anything else so that is what I have been using in their diff for the past 4 years.