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2004 SRT4
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Discussion Starter · #1 ·
Ed Peters (RIP) suggests a high mileage Mobil 1 10w-40 for our transmission to give a high shear resistance thanks to zinc. On the Mobil spec sheet the Mobil 1 4T 10w-40 has 1390 ppm v 900 for the high mileage.

My 40,000 mile one owner 2004 has the original fill and I am prepared to try Ed’s suggestion, but using the 4T synthetic. He doesn’t add the organic friction modifier because it degrades the synchronizers over time.

Anyone have experience with Mobil 1?
 

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My understanding is that the oil contents have changed since those series of videos were posted, however if the spec sheet maintains that, it might still be correct.

Of course, you will get 10 million answers on this; everything from Royal Purple to Liqui Moly variants.

Personally... I have run ATF with FM for 100k kms with no issues historically. Currently I have ATF in one car (without friction modifier), and 10W-40 HM in the other. I rev-match and double-clutch, so I am less likely to have issues, but that being said... the ATF is a little more chattery, and the 10W-40 HM definitely has a stiffer feeling to it until it's warmed up.

I have no transmission issues in either car currently (knock-on-wood).

However, I'm not putting serious mileage on either car, and likely replacing those fluids far before their actual service interval.
 

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However, I'm not putting serious mileage on either car, and likely replacing those fluids far before their actual service interval.
I'm sure you've seen this Bill, but other maybe not. Factory service interval for the ATF was reduced to only 18,000 miles for the typical Schedule B.....maybe for the friction modifier/synchro issue?

I've always ran ATF with FM, but am going to try without the FM next time.
 

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I'm sure you've seen this Bill, but other maybe not. Factory service interval for the ATF was reduced to only 18,000 miles for the typical Schedule B.....maybe for the friction modifier/synchro issue?

I've always ran ATF with FM, but am going to try without the FM next time.
Yep, those inserts were in my owners' manual back in '04 and since car #1 I've done trans fluid before 30k, usually with plugs and wires.

Thanks for posting it up - most newer owners today I'll bet don't get the inserts, let alone the manuals included with the car.

I recall coming across several explanations about the FM degrading the ATF fluid, which is why the interval was reduced.
 

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Yep, those inserts were in my owners' manual back in '04 and since car #1 I've done trans fluid before 30k, usually with plugs and wires.

Thanks for posting it up - most newer owners today I'll bet don't get the inserts, let alone the manuals included with the car.

I recall coming across several explanations about the FM degrading the ATF fluid, which is why the interval was reduced.
I got lucky, mine came with everything but the window sticker 😂
 

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Discussion Starter · #9 ·
Thanks, everyone for your input. I am going to use the Mobil 4T “Racing” 10w-40 because Mobil spec sheets plus drivetrain engineer Ed Peters remarks have weight. I am also investing in a Hurst shifter from Modern Performance. I had a Mad Dog in my 2005, liked it but I am hoping for a crisper shift feel. I drive like the old man I am, but still enjoy the SRT4 experience.
 
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