ROYAL PURPLE GEARBOX 75/90

Depending on where you look; references are for GL4, GL4+ and/or GL5.

But yeah, pick a good one and change it every year (that in itself will reduce chances for corrosion). Plus, most of us are lucky if we can drive these old cars more than 1000 miles a year as it is.

I posted this in another thread:
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Sure...lets discuss motor oils next...

 

These are extracts on oil contamination and brass corrosion from a study I posted earlier.
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I decided to bump this thread as I am about to do my annual fluid change. Has anyone sent in a used oil analysis since this thread was last active? Still trying to decide if a GL-4 or GL-5 oil is the best long term option for my 355. I'd love for someone to tell me they have been using a GL-5 and have a oil analysis with no excess copper in it. Such a dilemma...it essentially seems like a trade off between protecting the synchros and protecting the differential.

 

The factory specified (approved) oil is Shell Transaxle Oil 75w90 (now called Shell Spirax S5 ATE 75w-90) which is GL4/5 oil. An expert says "You need to realize that an oil with GL-4/GL-5 on the label is a GL-5" (extract from a document by Richard Widman). In this case, I wouldn't worry about using a good quality fully synthetic modern GL5 oil. The same expert also says that "Somewhere around 25 years ago a deactivated or buffered sulfur was developed that would react with the phosphorous to create the protective/sacrificial layer in the conditions created in the gear boxes (temperature and pressure) without being corrosive to the brass, copper, etc. This additive system is used in most gear oils today." If, however, you prefer to follow the Ferrari specified Shell, you can still get it (Shell Spirax S5 ATE 75w-90) but, it seems, only in 20 Lit. pails.

 

Sorry, I have no idea how the link jumped in.

 

To partially quote Dave I think it matters especially since Bob showed the 75-90 shockproof was not the greatest.
Also to point out what someone said about not putting very many miles, this probably has more to do with it. Not too many people on here drive enough to get a great test of durability, and then you have the other variables, do they let the oil get up to temp, do they drive th car hard or easy, how hot does the oil get.
As a person starts to think about it Fbb statement becomes more and more true.
Most of us likely change the oil way more than we need to as well.
Just an observation

 

I use it. And it's fine shifts nice and I put on about 15k a season. I drive it every day

 

Just changed my trans fluid with Redline 75-90 MTL and their standard trans oil. It's just what I had lying around, no science experiment. It's been, let's see, 3 years? Maybe 4 since the last change. Can't rightly recall. The stuff came out looking like crap. And it stunk. So, yeah, these regular change intervals kind of matter.

 

Hey Vince, I changed mine in the 355 with Redline 75-90 NS. What's the difference between the two?

Doing the 612 with Mobil 1 just to be different.

 

Hi Vince

About how many miles were on the oil??

 

LOL, you know me Grant. Like 3000 maybe.

 

Peter from what I studied and was told the ns was better for our transmissions. But it seems for every side there is thenother side.

The mtl was not the bad one from what i remember. Bob said he thought the shockproof was what gummed up his i believe.