boostededge Posted October 7 Report Share Posted October 7 Since the 2019+ ST's call for 75w85 has anyone tried the Amsoil for a decent chunk of miles? https://www.amsoil.com/p/amsoil-severe-gear-75w-85-100-synthetic-gear-lube-svl/ That is all! 1 Quote Link to comment Share on other sites More sharing options...
Samurai Edge Posted October 23 Report Share Posted October 23 I have never used AMSOil products so I can't say. The PTU calls for Motorcraft XY75W85QL ( Synthetic ), which is ridiculously expensive. As an option, you can use either one of these. I use the Motul. Red Line 50104 75W85 GL-5 Hypoid Limited Slip ( Full Synthetic ) Motul Gear 300 75w90 105777 ( Full Synthetic ) Quote Link to comment Share on other sites More sharing options...
boostededge Posted October 23 Author Report Share Posted October 23 (edited) I went with the Amsoil SVG 75w85 in the PTU. The guys on Bobistheoilguy said the 85w would run ever so slightly cooler than a 75w90. And it makes sense to put a better than factory fluid back in. Theres a big Gear Oil Test thread where they test all the popular 75w90 gear oils on the market and the Amsoil came out on top of everything for the most part. Flash point, 4-ball wear, etc. Edited October 23 by boostededge 1 Quote Link to comment Share on other sites More sharing options...
1004ron Posted October 23 Report Share Posted October 23 About 5 years ago I switched all my vehicles over to Amsoil SVG. I did this based on the widespread independent reviews that included lab results. 1 Quote Link to comment Share on other sites More sharing options...
STBEAST Posted October 24 Report Share Posted October 24 I agree. When it comes to parts you can't go wrong with OEM. It's a no brainer. But when it comes to lubricants, in many cases there are better options. And there are some good ones: Amsoil, Red Line and Motul are by far the best. The key is Full Synthetic. I plan on going with Red Line for my PTU/RDU. Any suggestions from you guys on the transmission fluid? That's the one I haven't done any research on. 1 Quote Link to comment Share on other sites More sharing options...
STBEAST Posted Sunday at 04:39 PM Report Share Posted Sunday at 04:39 PM I went on the Amsoil website and found the 75w85 for the PTU, but did not find the 75w specifically to the RDU. Does Amsoil have a compatible RDU fluid? Redline offers a full synthetic 75w for the RDU. Quote Link to comment Share on other sites More sharing options...
1004ron Posted Sunday at 08:14 PM Report Share Posted Sunday at 08:14 PM On 10/23/2025 at 9:06 PM, STBEAST said: Any suggestions from you guys on the transmission fluid? That's the one I haven't done any research on. I've searched and contemplated switching but have stuck with the OEM trans fluid because of the mixed responses I found. This is what I was considering: Valvoline Multi-Vehicle (ATF) Full Synthetic Automatic Transmission Fluid Quote Link to comment Share on other sites More sharing options...
1004ron Posted Sunday at 08:16 PM Report Share Posted Sunday at 08:16 PM Wonder what's behind Ford switching from the 75-140 to 75-85 for the PTU ? Quote Link to comment Share on other sites More sharing options...
STBEAST Posted 19 hours ago Report Share Posted 19 hours ago I don't think you can go wrong with Valvoline. Seems like you are making a good choice. With regards to the change from 75w140 to 75w85 for the PTU- It could be just like the motor oil, for better fuel economy. And better flow for improved cooling and performance. Quote Link to comment Share on other sites More sharing options...
dabangsta Posted 10 hours ago Report Share Posted 10 hours ago 8 hours ago, STBEAST said: I don't think you can go wrong with Valvoline. Seems like you are making a good choice. With regards to the change from 75w140 to 75w85 for the PTU- It could be just like the motor oil, for better fuel economy. And better flow for improved cooling and performance. Or a completely new type of PTU with the disconnect? 1 Quote Link to comment Share on other sites More sharing options...
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