cbracer

I've searched a bit on different forums and collected some information, but still not sure what to use. It seems the dealers buy in larger quantities and don't always use Mobil 1 or other approved oils. I doubt they carry separate types for the older 2.5l boxster compared to all other Porsches, so they put the same thing in all Porsches. That means many of you guys with 2.5l boxsters might have the wrong fluid in it.

Now the two ratings are GL5 and GL4, each one is different due to the alloys used in the tranny. Some have friction modifiers or slippery additives and some don't. (mainly for limited slip)

The 2.5l boxster has a 5 spd that's also used in Audi's. It requires GL4 rated transmission fluid which was made by Burmah and got bought out by BP. Mobil One does not make GL4 fluid.

Most other Porsches like the 996 take a GL5 rated fluid:
Shell Transaxle (75W-90), 999.917.546.00 for 1 liter bottle
Mobil Mobilube PTX (75W-90), though I don't know what PTX is compared to their standard synthetic stuff.

Other non approved fluids that people have used:
Redline MT-90
Redline 75W/90 NS (2 parts) mixed Redline Lightweight Gear Oil (1 part)
Royal Purple (claims to be compatible with GL4 or GL5) has friction modifiers in it
Pensoil for GM cars

Does anyone have more information they can add or suggestions? Thanks,

GMS

If the dealer was using non-Porsche approved oils, that would be against the franchise agreement and I doubt is any (whatever make they represent) dealer that would risk a multi-million dollar business for using the wrong oil.

As 996/986 manual transmissions oil changes are rarely done, it's unlikely that incorrect oil would be used.

cbracer

Many dealers are putting in Mobil 1 fluid that is GL5, not GL4 rating. If you call Mobil 1 they will deny making fluid for the 97-99 Porsche Boxster. Most dealers are using Mobil 1 (in 97-99 boxsters ) as it's approved GL5 fluid for all other transmissions. Some dealers aren't using Mobil 1. I know this for a fact. Sure they can put GL5 fluid in GL4 transmissions, but some metals in GL4 transmissions will wear down faster with GL5 fluid.

GMS

If this is a confirmed and proven fact, it is your responsibility to contact PCNA as they administer warranty, dealer and customer relations.

cbracer

I'm not here to get into an argument with you. And I'm not here to prove dealerships put GL5 into the 2.5l 5 spd transmissions which specify GL4. They do. It's wrong. But they get away with it because it doesn't cause drastic failures in short time frames. PCNA understands that dealerships aren't going to stock barrels of 2 different fluids when only 1 is used for the 2.5l tranny. PCA even admits that Mobil 1 GL5 fluid is an acceptable replacement. That doesn't mean it's the right stuff. I'm only looking to find the right stuff to use and you're not helping.

GMS

I have a litre of 999 917 546 00 75w/90 gear oil in my hand right now, it is Porsche approved and supplied oil for all 986/996 and is $39.00 per bottle.

David A

Redline is great stuff and Mobil 1 too.

Larry L

I have four quarts of Redline that I picked up for a specE30 project that didn't materialize. I used Redline in an e30 that i had three years ago, and it absolutley transformed the drivetrain in that car. I'm hoping it will have similar results in the Boxster.

A trans fluid swap is going to be my weekend project.