manual gear oil suggestions? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I was going to change my gear oil in my 2002 S manual this weekend, but I can not seem to find two people that agree with what to put in there. the car has 65K miles and I drive in south texas heat. What brand and weight oil would be the best regardless of price? Also does anyone have a DIY link for this? thanks, James

Call Sunset [phone removed]) as they usually have a little better pricing: http://www.e-partssales.com/miva/merchant.mvc?Screen=PROD&Store_Code=P&Product_Code=99991754600&Category_Code=986Tran

There is a basic reason why you cannot get agreement on what type of gear oil Porsche uses; because they use a totally unique product that is made just for them. As the result, most major gear oil companies (the truthful ones anyway) simply say they do not have a suitable replacement, while the hucksters will tell you theirs is a perfect substitute…… Knowing how much these gearboxes cost, and that the OEM fill is a readily available and inexpensive full synthetic product, going to Sunset and buying the OEM fill is your best bet.

There has been a lot of postings on oil and some are pretty comprehensive. I remember reading a great one by Charles Navarro on why he does not recommend oil but if you go to LN engineering's site you will see what they think is good enough to distribute. I replaced mine recently with Royal Purple and ran TTs, AXs and DEs without any noticeable difference. (I'll try Motul next). For the DIY, Bentley's is your best help. Not too bad of a job (Except measuring the oil level).

What??? Jhandy is asking about manual gear oil....not engine oil. And yes, Charles clearly recommends specific oils on his web site. Did you read his entire "Freq. Asked Questions" link? Excellent reading. You will see that he recommends specific oils, and recommends oils to shy away from (like Mobil 1).

The OEM fill on race cars from the factory used to be (and might still be) Mobil 1 SHC, which was rebranded under their industrial lube name Delvac 1. We've used it for years, when it was only available in 55 gallon drums. I used to even bottle it for customers, until Mobil started offering it in gallon jugs. It's different from the M1 gear lube found at Autozone, etc., and I've used and recommended it for years.

Charles, an interesting response, particularly in light of the fact I had read the same explanation elsewhere and asked our Mobil rep about it some time ago, got a totally confusing answer and then was referred to their “technical group” who responded, “Mobil no longer produces a suitable gear oil for the Porsche transmission. You should consider contacting a Porsche dealer for an appropriate replacement.” Any thoughts?

I would file that response under the cookie cutter answer. If I ask my Mobil rep, they wouldn't know what a Porsche was :-) - just a bit of an exaggeration, but you get the point. Since the gearbox is sourced from VW/Audi, it would take the same fill and their lube may be a fully-synthetic GL-4 rated gear oil. There are VERY few true GL-4 oils available, most out there are GL-5 rated (which is supposed to be backwards compatible). The tip's differential on the other hand calls out specifically for a GL-5. Technically, any 75w90 or 90WT GL5-rated gear lube should meet the requirements for the gearbox IMHO. It's best to google about vw/audi gearboxes rather than Porsche ones, since you'll find a lot more information and discussions about the vw/audi counterparts to the Porsche ones.

I have less respect for Mobil 1 everyday............ Just for informational purposes, Red Line continues to offer a good selection of GL-4 full synthetic gear oils. Reason I know this is that Nissan continues to require GL-4 gear lubes and the syncros (and some bearings) they use don't seem to last very long with GL-5 oils. We've used the Red Line GL-4's in our client's Nissans with great results. For what it is worth, under the API specs, the additives’ that make a gear oil a GL-5 should make the oil incompatible with a GL-4 gear box. I know some oil companies have claimed to have oils that can be used in either one, but having seen what a GL-5 oil does to the internals of a GL-4 Nissan gear box, I really wouldn’t trust the claim that a GL-5 is always backwards compatible………….

I saw this on another site, you may be interested: https://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/Group_3_Base_Oils.aspx

Not exactly "news", they have been doing this ever since Exxon acquired Mobil in December of 1998, which is why the performance of their oils has deteriorated so much since the acquisition, and why some grades no longer carry ACEA ratings……..

We do have some decent long term testing on the Delvac 1, for what it's worth, with the aircooled guys. Many tranny rebuilders, including Guard, recommend it. Amsoil also makes a GL4 oil, that I used to use in 356 and VW gearboxes before switching to Swepco 201, which anyone before a 915 gearbox swears buy. It's also a GL5 rated oil, for what it's worth. Interesting you mention Nissans - one of my customers mentioned their use of Motul in their race trannies (and engines) with excellent results.

Can honestly say that I have no history with Mobil Delvac synthetic gear oils, in fact, I don't know who even sells them. Did a quick online search, lots of data but nothing on were to buy. I'll have to make some calls in the morning. Motul has several interesting products, only problem is that they tend to be very expensive to buy unless you get large quantities, kind of restricting. I've used their stuff as well, and it was fine, albeit pricey.......... Never been much of an Amsoil fan, but only because of their weird MLM-like distribution system, and because history has taught me to shy away from small blenders and stick with larger producers.

I did find that Mobil does make a Delvac 1 synthetic transmission fluid 50, which is equivalent to a 90WT, which carries a GL4 rating, which is also now available in gallon jugs. Something worth asking your Mobil rep about.

www.redlineoil.com

Always use the OEM lube from Porsche. It is formulated with all the correct additives to get maximum use of syncros. If a lube is too slippery, as many are you will get an occasional grinding in second mostly however it can occur in other gears too. When it grinds you are damaging the cogs on both the gear and syncro. Eventually it will always grind and subsequently slip out under a load. A GL4 is what to use and if you contact Mobil you will find they tell you not to use their GL5 product. Replacing the lube under 100k is usually a waste of time and money anyway.

Based on what?

actual experience I have seen transmissions, both automatic and manual, limited slip differentials misdiagnosed because wrong fluids. I realize oil and other topics are passionate subjects for some with strong preferences however take what I said as not personal preferences. OEM transmission lube is the best all around lube for all around driving in a modern Porsche and many other brands.

You just have to be knowlegable about lubricant choices, that's all. Mobil's Delvac 1 isn't formulated for limited slip differentials. And yes, they do make a GL4, but again, it's not something found at your FLAPS. As far as drain intervals, if you ask a performance transmission builder that does Porsche gear boxes, I'm sure they'll tell you to change the gear lube more often than 100,000 mi. That's way too long. If you track the car, it should really be done at least every year. Same goes with the ATF on Tip cars if tracked. If not tracked, I would take Porsche's recommendation and cut it in half, at the very minimum. It's interesting to see manufacturers like Kia with their very good extended powertrain warranties and see on how short their drain intervals are.

"I realize oil and other topics are passionate subjects for some with strong preferences however take what I said as not personal preferences. OEM transmission lube is the best all around lube for all around driving in a modern Porsche and many other brands." Again, I fail to understand how the above statement can be made and not seen as "personal preference."