'11 Mustang Fluid Change Advice Please

[doitmyself]

My adult son bought a used 2011 Mustang this summer and is approaching 30,000 miles. The owners manual says the synthetic auto transmission and rear end fluids are good to 150K. Even the dealer said they are o.k. until at least 100K (odd, because they can make more $ servicing early).

Personally, I don't believe in the "lifetime" fluid idea, especially in the transmission. But, I haven't had a new car in 8 years and things have changed.

Have fluids improved THIS much? (like our longer engine OCI's)?

1). Opinions about the auto transmission fluid change? Yay/nay?

2). Rear end (little experience here)? Is that synthetic oil that great?

3). Final question: The car is going into winter storage soon. Do these changes now, or next spring? My thought is if done now, he won't drive it enough to check leaks, etc..

Thanks very much.

 

[MCompact]

If he's not tracking or hammering the car I'd go with 50k changes, although if the rear diff is limited-slip I'd change it every 30k.

 

[silverrat]

Originally Posted By: doitmyself
My adult son bought a used 2011 Mustang this summer and is approaching 30,000 miles. The owners manual says the synthetic auto transmission and rear end fluids are good to 150K. Even the dealer said they are o.k. until at least 100K (odd, because they can make more $ servicing early).


The $50 they make servicing it doesn't compare to the $$$ they would make replacing it when it fails.

I read a TSB for a F150 once that had no set interval for diff fluid change, where if the rear differential starts to make noise or if it's on it's way out, then you change the fluid and if that doesn't work then replace the differential.

 

[The Critic]

Originally Posted By: silverrat


The $50 they make servicing it doesn't compare to the $$$ they would make replacing it when it fails.

I read a TSB for a F150 once that had no set interval for diff fluid change, where if the rear differential starts to make noise or if it's on it's way out, then you change the fluid and if that doesn't work then replace the differential.


I don't think that's true. The dealer knows that on a high mileage car, most people will not be returning to the dealer for a replacement transmission anyway so they are much better off making more money from preventive maintenance, if it's truly needed.

 

[hate2work]

1) Yes, change the atf before 100k. Amsoil ATL is one of the best for that app.

2) Yes, syn gear oil is the way to go. Amsoil Severe Gear 75W-140 is what I'd use.

3) Not sure it would make much difference either way. If it had more miles I would say change it sooner rather than later, but with only 30k

 

[08_shelby]

I changed mine out myself at around 50k miles. Use synthetic only and use the correct weights listed in the owners manual. Check to see if the motorcraft friction modifier is required too.

 

[Jim Allen]

Originally Posted By: doitmyself

1). Opinions about the auto transmission fluid change? Yay/nay?

2). Rear end (little experience here)? Is that synthetic oil that great?

3). Final question: The car is going into winter storage soon. Do these changes now, or next spring? My thought is if done now, he won't drive it enough to check leaks, etc..

Thanks very much.


1) An automatic trans generates 75 percent of it's lifetime total of contaminants in the first 5,000 miles of operation due to break-in and the built in crud from manufacturing (they have improved this aspect the bast few years but...). When Eleftherkis and Khalil did their decades long study on transmission fluid contamination it left them with the conclusion that the oil itself isn't often bad, maybe even out to 100K, but it's the contaminants in it that accelerate wear. The built-in trans filter can only take out particles down to 80 microns and according to their tests, the most worrisome size in in the 15-20 micron size. So, I say "Yea" to the oil change. That or install an external trans filter to clean the oil up. Either way, the next OCI can be much longer.

2) Yes, synthetic gear oil is that great but probably the car has it already. The same thing applies as above. Right now the oil is full of break-in metals. Change it now, early, with a synthetic, and then make a long run the next time. The rear axle has no oil filter at all, so OCIs are usually dictated by use. Hard use, high heat uses up the additive package faster and vice versa.

3) Whichever is most convenient. I don't put too much priority on the winter part of the question but more priority on the "get that junk out" part. Just a few drives will tell about the leaks and in either the trans or axle oil change, the likelihood of leaks afterwards are not great, so that isn't a big worry IMO..

 

[doitmyself]

Thank you all. I did NOT get a wave of responses that I thought might indicate a change in attitude at BITOG, i.e.: "today's improved fluids and mfg. techniques make early changes in transmission and differential obsolete".

Jim, I was already aware of your transmission fluid stance on getting contaminants out, but was not aware if the contamination was also an issue with differentials. Your well educated, experience backed opinion is always appreciated (along with the others!).

I will advise him accordingly: to do it now is a good idea. If not now, certainly by 50,000. Next change can be longer (depending on driving style). Also, being used, he doesn't know the previous driving history.

Thanks again for the input.

 

[Garak]

Originally Posted By: doitmyself
Thank you all. I did NOT get a wave of responses that I thought might indicate a change in attitude at BITOG, i.e.: "today's improved fluids and mfg. techniques make early changes in transmission and differential obsolete".


I may be mistaken, but I don't think we've seen quite as many advances in drivetrain lubricants, at least in differential lubricants, as we've seen in motor oils. I don't know how the new Mustang is, but I have seen a few newer vehicles that actually have made it easier for such fluid changes. I recently did the differential on my G37, with around 30,000 miles on it. Some people I know said it was not necessary, but what the heck - it's not expensive and it's not difficult. I'm not saying I have to change it every 30,000 miles, although I certainly could, but getting the break in contaminants out can't hurt.

It also reflects something a lot of us have seen over the years. The engines aren't generally the weak point on the vehicle. The transmission will often fail before the engine, assuming we don't leave the engine oil in indefinitely, either.

 

[artificialist]

Replace the gear oil. It is cheap, and the gray slime created by gear wear destroys bearings.

As for the transmission, I'd say wait for 50,000 miles, unless you feel like you are in a real hurry to do it.

 

[D Hill]

The manufacturer is doing a juggling act here. They want the drivetrain to last at least as long as the warranty, but not so long that you're not buying another car from them for 10 years. The "maintenance-free" nonsense the manufacturer tells new vehicle buyers about the fluid in differentials and transmissions is helped by how much better good drivetrain fluids are now than they were 10 or 15 years ago, but they're definitely not at the point where you can put them in a trans or diff and never look at them again. Not without serious repercussions down the line (often for the second owner, something which the vehicle manufacturer banks on I'm sure).

I think you should be changing transmission fluid at 30K miles. Differential can go longer, out to 50K with no worries unless the car is at the track a lot; I changed the differential and trans fluids in my '11 GT at 10K to make sure I got all of that break-in crud out of it, and I'm going to do it all again at 30K. And then 30K after that.

I have 3.73s in mine, and while I can attest to the general bomber durability of Ford RWD differentials, when you have the power levels these new Mustangs have ([censored], even the V-6 has 300 hp) the fluid takes a beating.

Besides, changing your fluids halfway frequently even with Amsoil and the like is a [censored] of a cheaper than having a transmission or diff go sideway at some point down the line.

 

[Rhymingmechanic]

Originally Posted By: doitmyself
Also, being used, he doesn't know the previous driving history.


And being a used Mustang makes it more likely that it saw some hard use in those early miles, another argument for changing early.

If he's going to store the car for the winter, that gives plenty of time to decide what fluids to use, and he can change in the spring.

 

[Bror Jace]

I agree with Jim Allen & D Hill above. Give both these units at least one early change to flush out the break-in crud. I drained the factory gear oil out of my S2000's IRS diff with just 15,000 miles on the odo ... couldn't believe how nasty it was. Drained it again just 3,000 miles later to be sure the (expensive) unit was clean.

I don't put a lot of miles on the car ... will be a few years before I do it again and even then, it will be for a test to see how my choice of gear oil (Chevron Delo ESI) is holding up.

I'm not a fan of auto transmissions but the advice above is good. I'd do an early change (doesn't matter when, if it is about to be stored) and then again every 30,000 - 50,000 miles depending how it is driven. I really like the idea of an external spin-on filter set-up such as this:

http://www.summitracing.com/parts/BMM-80277/

Fluid is a lot cheaper then pulling and rebuilding components.