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This is how it is branded and sold. It's also sold as an ATF. While in theory most transaxle fluids can be interchanged as long as they meet GL-5 and are the correct weight (75W-90). He specifically says he used Mobil 1, which is sold as manual transmission fluid.
As for Shell Spirax S5 vs S6 - looks like the difference is S6 is designed for industrial applications, S6 is for automotive. Also, it appears S6 is GL-4 only. So based on this alone I'd suggest S5 to your original questions. The Mobil 1 fluid is also GL-5.
I called Mobil and Shell and both told me their system says its manufacture specific fluid and they don't have an equivalent. Shell actually told me their Spirax line doesn't have approval from Porsche. Since I have the base model with the open differential, they told me I shouldn't worry about putting fluid with the LS additive but not the other way around. I am almost at the point of just paying the $50 per quart at the dealer instead of trying another fluid that might cause over $100 in repairs.
I called Mobil and Shell and both told me their system says its manufacture specific fluid and they don't have an equivalent. Shell actually told me their Spirax line doesn't have approval from Porsche. Since I have the base model with the open differential, they told me I shouldn't worry about putting fluid with the LS additive but not the other way around. I am almost at the point of just paying the $50 per quart at the dealer instead of trying another fluid that might cause over $100 in repairs.
They didn't happen to say what was specific about it, did they? Usually if there is something specific there is at least some information about what it is.
@ciaka how did your research go when deciding to go with the Mobil1 fluid? Any ill effects?
My diff fluid and car are just fine. No adverse effects after what? Over a year?, year and a half?
Porsche will tell you to use some fluids that they charge you 100 dollars/quart for, and other folks, via chemical analysis have proven oils at 7 dollars/quart being just as good.
Porsche dealer know they have a huge revenue stream from repairs. It is up to customer to learn and make decisions about their property.
If I walk into Porsche dealer today, ask them to look over the car, despite it being in tip top shape, they would 'find' at least 10k worth of doing. Its their business, to take money from folks who are willing to give it to them.
I cross referenced the Shell oem fluid to this one via research and talking to a couple dealer mechanics. Been a while though.
Bottom line, if you are not confident 100%, pay dealer for change, or put in whatever else makes you feel 100% confident.
I am 100% confident in my choice via hours and hours of leaning and researching.
As mentioned, the fluid works great and serves my car perfect.
Originally Posted by tallpaul
They didn't happen to say what was specific about it, did they? Usually if there is something specific there is at least some information about what it is.
@ciaka how did your research go when deciding to go with the Mobil1 fluid? Any ill effects?
Thanks Ciaka for the response. I always do my own work and thank you for sharing your DIYs. As for the fluid you used I cant seem to find it in local shops and am only finding the regular mobil 1 with LS. Did you have to order it?
Just looked and I ordered the fluid on Amazon.com.
47 bucks for a gallon.
Hit online, easier to find.
Originally Posted by tastefulmod
Thanks Ciaka for the response. I always do my own work and thank you for sharing your DIYs. As for the fluid you used I cant seem to find it in local shops and am only finding the regular mobil 1 with LS. Did you have to order it?
Thanks Ciaka for the response. I always do my own work and thank you for sharing your DIYs. As for the fluid you used I cant seem to find it in local shops and am only finding the regular mobil 1 with LS. Did you have to order it?
If you can't find the Mobil-1 it does seem any GL-5 75-90 would work as well, based on Ciaka experience. Though Mobil 1 is great there are likely a number of other options available locally and online.
Some more info I have gathered from Liqui Moly. If you would like to use Liqui Moly and have the open differential you will need the GL4+. If you have the limited slip differential I was advised to use the higher viscosity 75w140 as their 75w90 GL5 does not meet Porsche spec.
I also looked at Red Line (ran it in my EVO and loved it) and they appear to support that specific part number + the specific SAF Carbon Mod and SAF-PD the diffs need. I think this is the one I'm going to go with unless I find something more compelling.
Not 100% sure if that is what everyone says by "Porsche Spec" but seems pretty accurate. Looks like Castrol and a few others have SAF CArbon Mod/SAF-PD complaint 75W-90 GL5+.
@tastefulmod Surprised they recommended a 75W-140.
Last edited by tallpaul; May 14, 2020 at 05:50 AM.
ya there is a difference between the oil for the LS rear differential and the non LS differential (open differential). I was surprised as well that they would recommend the 75w140. He mentioned to me that if the fluid causes damage to my differential that they will cover it. I will give this fluid a try and post back in maybe 6 moths time unless things go south before then lol
