bruce7

Interesting thread. Race cars with sequential gear boxes and steel syncros
differ though quiet a bit from street cars. In general, track cars to street
cars is an apples to oranges comparison. I think how the car is used will
determine which lubrication product is best suited for the job.

My conclusion is this:

Mobilube PTX was developed to provide outstanding performance specifically
for the 911 transaxle. Mobil Delvac was not.

Mobilube PTX is Porsche approved, specified and is the factory fill for 911 street
cars today. Mobil Delvac is not.

Porsche has done hundreds of thousands of miles of testing over many years
with Mobilube PTX and feels confident that it is the product to use.

As near as I can determine, Mobilube PTX was released around 2001,
well after 993 production ended. Unlike the case with engine oils, where the
air-cooled engines benefit from Mobil 1 15w50 and the water-cooled engines
benefit from 0w40, transaxles of current 911 street cars do not differ much
from the 993 days. Mobilube PTX applies as well to the 993 street car as it
does to the 997 street car.

I don't buy into the lifetime fill concept, nor waiting until 50k miles to change
the oil. Based upon driving use, I think it should be changed more frequently.
I change mine every 20k miles. Each time I do, it comes out cleaner than
before with virtually no debris attached to the magnetic drain plug.

I'll stick with Mobilube PTX. It works for me.

Ed Hughes

Another point in comparing track use to street is that often the mechanicals on the race cars get torn down on at least a semi- regular basis for rebuild or inspection. To me, that is a different service life than what any of us are looking to get out of our mostly street cars.

Mike J

I asked Bob at Sunset about it. Here is the quote:

PTX only comes in 20 liter containers $472.78 000-043-204-20
Porsche also has Shell oil 75w-90 in 20 liter container $399.11 000-043-204-19
The shell does come in one liter container for $25.38(we normally have this in stock) 999-917-546-00

The PTX stuff is $23.64 per litre - YIKES!

Cheers,

Mike

bruce7

Hey Mike,

Those are great prices. I know about the Shell Transaxle oil, I actually used it
once on a Boxster. It was hard to find back then. The next time I went to get
it there was none in country and that's when I found out the dealer would sell
me the PTX if I brought a suitable container as they had none to provide.
From what I recall, the Shell Transaxle oil is also approved by Ferrari.
Here's a couple of old photos of a DIY trans oil change with Shell Transaxle.

-bruce

ToSi

here's another thread to consider -> https://rennlist.com/forums/996-gt2-...l-for-gt3.html

PTX sounds like the newer & 'better' oil, whether it provides benefits over delvac is unknown. Only apparent downside is cost though...

KaiB

FWIW, my builder wants me to use Delvac. He has reasons for this, the nay sayers won't agree anyway, but I far prefer the advice of a highly regarded pro.

Mike J

I filled Delvac on my Turbo this spring - it changed the shifting to excellent to sometimes excellent, sometimes balky. This is the SHC stuff. I do not know what was in the transmission when I dump it, did an oil analysis and it might be original fill.

I will dump the oil soon into a clean container so I can put it back and experiment with some other oils - hopefully some will restore the car back to its old shifting patterns.

Cheers,

Mike

Cactus

3 years ago when I changed mine using Delvac...I put the whole gallon in but none ran back out.

GTgears

I don't disagree with any of your above statements, though see the bold. Do you know why they developed PTX? Because the 996 GT3 has steel synchro rings on 3rd-6th gear. The ONLY real difference between Delvac and PTX is that they put in some friction modifiers in the PTX to make it a little more slippery so that it has better cold shifting characteristics. They did that because the steel synchros can be baulky when cold.

But that also has a secondary benefit to people like you guys who drive 993s, which have brass synchros in 3rd-6th. Your 2nd gear triple ring synchro is identical to the GT3s 2nd gear synchro. A common complaint that both 993 and GT3 owners have as their cars go up in mileage is notchy and difficult shifting into 2nd gear in the cold. Those same friction modifiers that were put into the oil for the steel synchros on 3rd-6th help that 1st to 2nd shift in the Winter months. Even for those of you in California, Florida, and Texas, it is cold enough in the Winter for that behaviour to exhibit itself.

This is why time and time again on these forums I tell people that there is no one size fits all and that I do not explicitly endorse any one oil. You will do no harm by putting PTX in your car. By the same token, if you don't drive like a drag racer during warm up, you will also do no harm to your car by putting in Delvac. Delvac offers slightly better hot protection, whereas PTX will offer slightly better cold shifting. They are really shades of gray, and which one you think is the prettiest is up to you.

ps. I disagree with the factory on a lot of things. For example, I think you are a fool if you follow the factory service interval on your gear oil changes. 15k mi or every 2 years, whichever comes first. Porsche's gearbox service intervals are irresponsible.

JasonAndreas

A not-so random sampling of owners here (myself included) over the years has not shown Delvac/SHC to be of any benefit to stock gearboxes & brass syncros with this problem. If anything, the only thing reported to have resolved the cold notchiness problem is the $tupid expensive OE PTX lube.

The differentiator seems to be the syncros?

GTgears

Jason,
I'm not sure you read my comments correctly. What I was saying is exactly what you said, that the advantage of the PTX is that it is one of the few gear oils that solves that notchiness. I never said that the Delvac will solve it because it won't. I said that if you are going to put Delvac into your gearbox you need to not drive it like a gorrila while it warms up because if you push it hard right out of the driveway the Delvac will most definitely crunch on the 1-2 shift.

JasonAndreas

You are right, sorry!

Slow Guy

GTgears, thank you for your input.

nine9six

From the Suncoast site:

Mobile 1 Mobilube PTX 75W-90

Transmission fluid for 2001-2012 Turbo & GT3 models with a manual transmission.

One liter. Order as needed. Consult your owners manual or a technician before using any fluid.

From GTgears 1st post:
Mobilube PTX is Porsche approved, specified and is the factory fill for 911 street cars today.

The common thread appears to be (2001-2012 Turbo & GT3 models & factory fill for 911 street cars today)

I think unless you have a 993 turbo application; we are not comparing apples with apples.
NA street going 993's are not seeing or carrying the laods of a turbo unless the NA car is slamming gears in a racing application.
Just my $.02

Cactus

My exact symptoms with Delvac. 1-2 is stupid until I drive the car for 20 minutes then it all smooths out. I do have an issue with 3-4 though and it sometimes gets caught going into fourth. New RS mounts and still the same issue although shifting at higher rpm's is better.