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Why did Porsche tell us for ten years that the correct oil was a 0W40 ?
10 Years? I thought they switched to 0w-40 in 1996... I have documentation from Porsche recommending you fill the 993 (like they did when your car was delivered from the factory...) with 5w-40 going back to its introduction. Manufacturers have always recommended a range of oils according to the operating environment. So we shouldn't get hung up on weights.
This is the problem - we should NOT have to 'imagine' what the benefits are. They should spell it out. Not simply tell us 'it is better'. Why did Porsche tell us for ten years that the correct oil was a 0W40?
Originally Posted by JasonAndreas
10 Years? I thought they switched to 0w-40 in 1996... I have documentation from Porsche recommending you fill the 993 (like they did when your car was delivered from the factory...) with 5w-40 going back to its introduction. Manufacturers have always recommended a range of oils according to the operating environment. So we shouldn't get hung up on weights.
Here the is original Porsche oil recommendation taken directly from my 993 owners manual.
Note that Porsche did not recommend a 0W40 oil for any temperature range, even cold weather use.
Also note the specific recommendation to Not utilize thin oil viscosity ranges (0W) for general use.
I am going to stick with Mobil-1 15W50 full synthetic as Porsche specified with the proper Zinc and Phosphorus levels at the time of the oil service API SH (1200/1300)
Last edited by FlatSix911; 03-22-2015 at 09:00 PM.
Though I've been using Motul V300 15W-50 in the last 5 years with excellent result (when i drain in, it comes out as new...!), i' ve always been concerned about high oil pressure at operating temperature (5 bars @ 2500 rpm). I feer it's too much...!
Outside temperatures here ranges from 0 to 40 C. Car is at 175.000 km.
Now, because I've always believed lighter oil will flow better, thus reach every point of the engine faster and more aboundantly, excange heat easier, make less resistance (less heat) and lubricate better at strart up, last oil change I swapped to 5W-40 API SL and now the pressure looks better to me: 5 bar @ 3500 rpm.
Am I the only one concerning about eccessive oil pressure? I would much apreciate some expert suggestion!
The 993 is the only air cooled 911 with hydraulic lifters and I recall the recommendation of 0-40 had to do with the lifters. And, that is what Joel the 993 PCA guy continues to say. So, after all these years why is this still not believed? I use it in my 95 but add the GM EOS. If I add any oil I use 15-50. I like most am puzzled by PAG in regard to Classic, Mobil 1 and air cooled, solid lifters vs hydraulic. PAG is supposed to be the worlds greatest automotive engineers but with this and the IMS I wonder are they what they used to be.
Went back and replayed the video of Porsche Classis representatives talking about the classic oils and they did not state that the Porsche Classic oils were the best, the said in independent test their air cooled specific oils tested "outstandingly good" compared to other broad based engine oils. The tests were said to have been conducted by two well know classic car magazines in Germany. Anyone have knowledge of these tests?
Here are few rocker arms from various 911 / 'Mezger' aircooled 6 cylinder engines, pictures borrowed from various places online:
The part that contacts the cam lobe is this pad:
You'll notice the lobe slides along the face of the rocker pad, hence the term 'slider tappet'. This is significant since the entire width of the lobe engages the rocker.
A typical 'flat tappet' isn't truly flat. It has a crown in the center & the cam lobe is tapered to force the lifter to rotate, evening wear. The actual contact area between the 2 is much smaller than a sliding tappet:
This small area, combined with high (100lb+) seat pressures & valve spring rates required to control the valve train in sporting OHV V8 engines can result in extremely high contact pressures (200,000psi+), resulting in these engines' increased sensitivity to oil quality in this area.
but back to the Mezger flat-6.. without pushrods to add mass & smaller valves, they generally can use lower seat pressures / spring rates to maintain control. Since their rocker ratio is lower & resulting force applied over a larger surface area of the cam lobe, it should be clear that observed pressures at the slider pad are much lower.
Circling back to the zddp part of the story, you'll notice the A40 Porsche approved flavors of Mobil 1 are higher in Zn & Ph vs. most of the others(mobil-1-oil-product-specs-guide.ashx). Of course there's more to wear than just those 2 ingredients but it suggests that someone who presumably knew what they were doing evaluated these oils before declaring them OK.
Not sure what the rest of your post means but the 4 valve engines use bucket tappets. Smaller valves = less mass so lighter springs can be used. Also they are direct actuating so contact pressure at the lobe isn't magnified by the rocker ratio.
As I mentioned in the other thread, would love to see an engine w/ a scored cam lobe (not due to a blockage or other mechanical issue) that was using Mobil1 0w40 or other oil approved by those 'marketing clowns' in Weissach. I would be more concerned with buying oil from boutique manufactures who pay refiners to mix up whatever recipe happens to be popular w/ the cool kids on the forums, but lacking a significant R&D budget to actually test their wares.
ToSi,
I used to have a ZDDP anxiety but after also realising that all the damaged 911 cam lobes and followers that I have seen on the internet were not damaged by the lack of anti-wear compounds but by a blocked oil jet or corrosion pitting I've realised that I was trying to solve a problem that doesn't exist.
I'm happy to be proven wrong but I'm yet to see any evidence rather than just internet hearsay that gets repeated so many times that it unfortunately gets accepted as fact.
Nowadays I don't lose any sleep about a few hundred ppm of ZDDP one way or the other and just use a A3/B4 spec oil as I think that's easiest and the best way of selecting an oil that suits our needs.
03-22-2015, 03:19 PM
