v8_ranch

OK, can someone settle this "myth" or "truth" for me please. I have always heard that it is not a good idea to switch from dino to synth oil in an engine (can cause leaks from seals). I have switched back and forth in vehicles in the past (non Porsche) without problems noted.

My question is: does it matter on the flat 6? PO of my car swore by Castol GTX 20w50. That is fine to me to use, but here is my even dumber question: can you use the Mobile 1 filters with dino oil? It is a synth filter, right? What about it is synth. Is there any compatibility issue at all? My reasoning tells me probably not, but thought someone out here probably knew for sure.

Thanks

ron mcatee

Always use factory filters on Porsche engines. After market ones usually don't thave the bypass capability that the factory ones have. By the way, what kind of car are you referring. Need to put that in the thread so we know what you want advice on. The only possibility of changing from Dino to Synthetic may be leaks. If you didn't have any, you are lucky.

v8_ranch

Oh, 83 cab with stock 3.0

Charles Navarro

I agree, factory filters. I do like the mobil 1 filter, but I just can't seem to find it anywhere for the later cars. It is superior to the factory filters in every way, but I would say since they do filter more that you should change the filter between drains on longer intervals - hell, you should do that anyways with a factory filter IMHO. K&N also makes an excellent resin impregnated filter that doesn't give up flow for filtration that is worth considering.

Mike Murphy

Everything I've read says that most cars don't leak when switching to syn. I say "most," because some do. Try to stay consistent with viscosity when switching to eliminate variables.

ron mcatee

I've heard negative info on the Castrol GTX 20/50 in 911 engines. I use Valvoline 20/50 VR1 Racing oil and the 75w90 synthetic gear oil in the tranny. I may switch to Mobil 1 full synthetic at the next oil change and the closest I can get to my current viscosity will be Mobil 1 15/50.

Ed Hughes

Don't forget the option of oil blends.....I run Castrol Syntec blend 20/50, and I'm pleased with how it seems to hold up. You get some of the benefits of synthetic (less breakdown, etc) and don't have the risk of the leaks. Valvoline DuraBlend is also good, IMO.

Charles Navarro

If you haven't looked up your oil on my oil page, you should:

http://www.lnengineering.com/oil.html

I would not recommend any castrol syntec product (with exception of the ones listed below), since they have some of the lowest Zn and P of all the oils I tested. Same with Valvoline's durablend. I would imagine the castrol syntec is similar in it's low levels.

Here's what Castrol had to say about Zn and P levels:

For those consumers that wish not to use a GF-4 oil in these vehicles,
Castrol does offer the following products that contain Zinc at a level that
is higher than the Zinc level found in oils (API SG) marketed during the
"muscle car" era of time:
* Castrol GTX 20W-50 (SL,SM)
* Castrol GTX Diesel 15W-40 (CI4,CH4,CG4,CF4,CF,SL)
* Castrol GTX High Mileage 20W-50 (SL,SM)
* Castrol HD 30 (SL,SM)
* Castrol HD 40 (SL,SM)
* Castrol Syntec Blend Truck 15W-40 (CI4,CH4,CG4,CF4,CF,SL)(Semi-synthetic)
* Castrol Tection Extra 15W-40 (CI4Plus, CI4,CH4,CG4,CF4,SL)
* Castrol Hypuron S 15W-40 (CI4Plus,CH4,CG4,SL)(Semi-synthetic)

The following Castrol products have Zinc levels that are typical of API SG
oil:
* Castrol Syntec 5W-40 (SL,CF)(Synthetic)
* Castrol GO! 10W-40 Motorcycle O il (SG)
* Castrol GO! 20W-50 Motorcycle Oil (SG)
* Castrol Grand Prix 4-Stroke Motorcycle Oil 10W-40 (SG)
* Castrol Grand Prix 4-Stroke Motorcycle Oil 20W-50 (SG)
* Castrol TWS Motorsport 10W-60 (SJ)(Synthetic)

Larry T

Hello,
Leaks tend to get worse if you already have them. But they seem to leak less after 10k-20k miles on the Synthetic. Like others, I've heard bad things about Castrol lately - I prefer Mobil 1 for it's heat protection and film provided during startup. I change at 4000 miles. Take a look at info on http://members.rennlist.com/oil where you'll find a link to Oil Analysis results which show the reduced levels of critical components in some oils. There's also tests of virgin Mobil 1 to compare the additives as they come out of the bottle.
IMHO, Mobil 1 provides the best protection for a great engine that can be very expensie to repair - an oil change is cheap insurance. Also, as others noted, use only Porsche approved filters such as Mahle. I've gotten great prices, service and OEM parts from buyeuroparts.com

Good luck!

srf506

SPider911,
How does the synthetic work in your gearbox? I've always heard the older 915 and 930 boxes needed a little extra "grip" for their synchros that the syn couldn't give you. We were always told to use Swepco in them.

Ed Hughes

Actually, the Castrol Syntec Blend 20w 50 was tested to be high in ZDDP by some in the classic British car community. Again, this is a semi-syn not the full syn. They use the Syntec name for both.

As of 10/06, they cited further reduction of ZDDP in the GTX family by Castrol, and only recommend the 20W 50 AFTER break-in.

Redline full syn got the highest "thumbs up".

Charles Navarro

Well, their information is not up to date. Since the beginning of this year, many "proven" oils have been reformulated to an API SM, and many that did have enough Zn and P, don't any more.

The list from Castrol was emailed to me just last week, so clearly the Castrol Syntec Blend does not have SG or higher levels any more (which I want in an oil), since it's not on the list.

I am retesting quite a few SM formulations now, since those tests I did late last year were on mostly API SL.

One particular oil that has drastically less Zn and P is the tried and true 15w50 M1, so just because it was good before doesn't necessarily mean the new SM formulation will have levels as found in the SL formulation. Same goes with diesel oils with the new CJ-4 standard.

Right now I only know of two oil companies that will continue to market a CI-4 separate from a CJ-4, and that is Brad Penn and Swepco. From the email above, it looks like Castrol also will not reformulate, but we'll see.

Larry T

When I 1st bought my 911 I didn't know about Swepco and used Mobil Synthetic in the Gearbox for my '74 911. It made it shift much better than the dino stuff the PO used although I plan to try Swepco in the near future. With the M1 it shifts smoothly and easily - from dead cold to fully warm. No complaints about M1. But I hear Swepco provides great service also.

ron mcatee

I find the consensus is to use Swepco 201 in the 915 trannies and Mobil 1 in the G50 hydraulic ones. My 88 Carrera shifts very smoothly with the Mobil 1. The PO of my 911 used plain old Valvoline 75w90 lube. As I always do with a newly acquired car, I drained and refilled everything to what I wanted.

Mike Murphy

Always a great idea. Besides, how can you know for "sure" what fluids were used.