Okay once again the age old question; What is best to run in an older 930? Several mechanics say that conventional is better because it will clot and not leak as much as synthetic. Right now I am running 15W-40 conventional with no problems but have always wondered if it is better to switch to synthetic.

Thanks

 

From the turbochargers standpoint, run Synthetic... Conventional oils cut the life almost in half... Due to carbon coking on the turbine side seals and inside of the bearing housing.. The carbon will cut the critical sealing surfaces.. Look at it this way.. The cost of oil vs the cost of a new turbo.. With the new technology of sealers that are out, leaking 930's shouldn't be tolorated..

 

How many miles after a rebuild/ring breakin period before using synthetic?

 

Rule of thumb 500 miles

 

Hi,
it is best to consider the "run in" with a 15w-40 mineral "mixed fleet" HDEO with an API rating of at least CF-4/SJ. 15w-40 is suitable for from -10C to 40C+.These oils will inhibit turbocharger (and other) deposits and maintain viscosity very well during run in - about 500 miles is enough if the engine is "driven" and not pampered

For long term use consider Mobil's Delvac 1 5w-40 (M1 SUV 5w-40 is the same), this synthetic HDEO is a very durable oil indeed and will be suitable for use from <-20C to 40C+

Search under "Oil Condition Report" on the 928 list here and this link may be of some assistance;

http://www.landsharkoz.com/techtips.htm

Check under "Lubricants for the 928"

I hope this helps
Regards
Doug

 

Thanks for the input.

Cost isn't the issue. I would run whatever is best. I understand the coking issue as well but I have asked 2-3 mechanics and they all say use 15W-40 conventional (mineral) oil instead of synthetic.

I drive 3000 - 5000 miles per year and track the car about 4 times. It gets an oil change every year. Is there any truth to the leaks caused by synthetics? My engine has not been rebuilt and I have around 85,000 miles on the 25 year old engine.

Also what weight is recommended for synthetic oil used during 50F to 100F ambient temps? (I live in Michigan) Currently I am running the 15W-40.

Thanks,

Tom

 

Hi Millhaus,
for me I would stay with a 15w-40 mineral oil considering your comments re engine age etc. I would use a HDEO however as these are better suited to your engine family

A Heavy Duty Engine Oil (HDEO) that is API rated as above (CF-4>/SJ>) and with a "mixed fleet" comment on the container (very important) is best in turbocharged engines
These oils have a High Temperature High Shear (HTHS) viscosity above Porsche's minimum of 3.5cSt and usually near 4cSt. They are extremely good at high temperature deposit control in turbos and in the piston/ring pack areas and will gently restore internal cleanliness (intake screens etc) a little over time. Typically they have excellent anti-wear additives surpassing those in some "car engine" oils

Early synthetic engine lubricants did promote leaks due to their structure of that time - 30 years or so ago. They were initially produced in low viscosities too which did not help either

Modern synthetic oils are tested to the same standards as mineral oils and must meet minimum seal swell and seal degradation standards. By and large they will maintain the same leakage/seepage level if replacing the same viscosity and quality rated mineral oil - some may improve it due to the levels of either ester (and type) or PAO's used. Due to their much better flow charateristics they may display a little less oil pressure - usually up to 0.5bar at hot idle

In a general sense and worldwide the mysteries of synthetic oils still confuse people - mechanics in particular. They have been around now (commercially available) for over 30 years. They were first patented in the late 1800s and the "Grandfather" of most modern synthetic lubricants was born in Germany during the early-mid 1930s

Regards
Doug

 

I agree with Doug with the age of your engine and the miles on it.. Don't switch, stay with what you have been using.. With the track days that you are attending, I'd strongly suggest a topend rebuild. Yes, you might have good compression and low leakdown, but you are battling component failures.. You exhaust valves and rod bearings need some attention... You've gotten some good life out of the topend, don't roll the dice if you don't have too.

 

I would definately stay with mineral oil. I have seen a number of cars switch over and the end result was unwanted leaks. They then tried to switch back and a lot of the leaks remained so they had to start changing out parts. As far as the top end rebuild, I would only break open the engine if required. I have an engine with 110k on it and it has never been opened up. These engines can operate a very long time from the factory with proper maintenance. I still do not understand the need to rebuild an engine every 30k. I feel that some mechanics pull it do so that they can stop the leaks and others do it just to get more hp. I think if left stock (.8 bar) these engines should go well over 200k.

 

Being that these engines are aircooled the cycle times and heat cycles suck the life out of the sodium filled exhaust valves.. They need to be replaced.. or you will have valve failure.. I have seen plenty of damage over the years with customers sending turbochargers into me and I have to tell them that that not only is there car not running well because of a bad turbocharger, but also because the engine has valve/material damage. I often find pieces of the valve embedded in the turbine housing.. For my recommendation, 60-70K would be the tops for running past a topend overhaul..

 

The reason some say synthetic will leak is because synthetic oils are labatory made. The actual molecules are smaller than the dinosaur oil thus they can leak past the seals. I have switch to synthetic in an old 930 with low milage and had no leaks. You could try it and see if it does leak then switch back. No harm will be done. Some here mentioned using HD truck oil and that would be fine for you application. There is also a truck formula of Mobil 1. You question about if you do switch I would use 15-50 Mobil1 or another brand like Valvoline or Red Line 20-50.

 

besides running it in 3 turbos 76,86, 01 996tt I used in work vans 165,000 ho change only add never a prob in the 86 just did a 60,000 service we cheched out the pistions , like new the tec could not belive his eyes its good stuff


thax steve por100x@yahoo.com