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All oe air cooled 911 flat 6's have flat tappets cams
btw Dr. Ing. h.c. F. Porsche AG, Hans Mezger was the lead designer of these engines
I don't know why any would no consider them to be Mezger engines
From the 996GT3 and 996t the Mezer design was adapted to water cooling(earlier in race cars of course) and these cars w/ DOHC don't use flat tappet cams and aren't as sensitive to zddp as the older SOHC air cooled cars are.
Thanks Bill - I had it in the back of my mind that the 993 was different in some way from the earlier ones and therefore requires less ZDDP for instance?
Thanks Bill - I had it in the back of my mind that the 993 was different in some way from the earlier ones and therefore requires less ZDDP for instance?
The two-valve air-ccoled engines employ stiffer valve springs compared to four-valve engines (of any kind) and these water-boilers do OK with the reduced levels of ZDDP.
Air-cooled motors need a minimum of 1200ppm Zn & P to protect all of the rubbing surfaces inside the engine.
All oe air cooled 911 flat 6's have flat tappets cams
No, they do not.
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.
I am by no means rushing out to change my oil preference to the Porsche classic, however it seems that beyond some judging the silly can it comes in, or the steep price, that there is a rush to judgement that the oil isn't superior. I beleive the oil has gone thru two independent tests against a number of other oils and according to Porsche their product did well. I wish there was more objective, unbiased data out there putting oils to the test. Beyond taking the ingredient labels at face value or word of mouth, I can't find much to base my decision on. The oil wars will continue to rage because if this. I admit I used Mobil 1 for years until I heard Brad Penn was a better choice with the ZDDP content changes. Again, I am satisfied (to the extent I have had no issues and seems priced well for the perceived value) with Brad Penn and not looking to change again, but I also admit this decision wasn't made with a tremendous amount of independent data/analysis to review. Maybe there is more head-to-head performance tests out there that would help us objectively evaluate oils? Or are the ingredients on the label enough? Obviously I am not a chemical engineer.
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.
The point was that all the air cooled 911 flat 6 engines are sensitive to the zddp issue because of the rocker/cam interface, no it's not flat but it does fit the description of needing more zddp than the later water cooled engines
Even if the oil topic is a recurring one I always find it interesting and informative and with every single new thread, interesting points come up, like the discussion about flat vs. slide tappets above. Thanks guys
On the Porsche classic oil, I fully agree it is a marketing exercise to make money but, at the same time, I very much doubt Porsche would not put on sale the best product they can out there. Expensive, sure. Re-branded product with a huge mark up, possibly but I am convinced it is what they consider the best. Why would it be otherwise?
I’ve seen in other thread a VOA of this oil and the Zn & P content was below 1000 ppm.
I would imagine that oil technology has move forward over the years and new anti wear elements have been found which may make Zn & P not necessary in as big amounts as before.
Been reading on oil on this forum for the last week... and it seems I still have for a month's worth of reading. Somewhere along the line I decided I would start sampling and analysing my oil as I go. With the $$$ involved in opening this engine, I think it's a safe insurance. After all the reading, I can see a concensus but I'm sceptical and like to see real numbers. I can see my next challenge, reading the numbers but then again, a lot of reading to do...
For what it's worth, I've put Amsoil in at my (first) last oil change, one of my daily is a beetle TDI, these are renowned to chew cams and lifters, everybody recommends changing oil every 5000Km... I did otherwise, running that same oil, I did my oil changes at 20 000Km or yearly. I just clocked 220 000Km, maybe that is why I'm sceptical by nature, reading is something but numbers and real facts usually don't fail me.
On the Porsche classic oil, I fully agree it is a marketing exercise to make money but, at the same time, I very much doubt Porsche would not put on sale the best product they can out there. Expensive, sure. Re-branded product with a huge mark up, possibly but I am convinced it is what they consider the best. Why would it be otherwise?
I’ve seen in other thread a VOA of this oil and the Zn & P content was below 1000 ppm.
I would imagine that oil technology has move forward over the years and new anti wear elements have been found which may make Zn & P not necessary in as big amounts as before.
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 ?
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'.
Yes, I agree. it would be great if Porsche gave a detailed description of exactly what additives to look for, what quantities and, more important, why, but they won’t (possibly because that would give away core knowledge). All we have is the Porsche approved oils list. I have to believe that every single oil on that list was put through a durability test and came out OK.
Let me say that I am not defending Porsche tactics; I think they are here to make money (like any other company) but at the same time I believe they know their stuff (well, most of the time... 991 GT3 engine etc. ).
Originally Posted by orangecurry
Why did Porsche tell us for ten years that the correct oil was a 0W40 ?
I am aware that 0W40 is in the approved oils list but did they recommend it specifically for air cooled engines in a service bulletin or something? (honest question; I don't know).
Recommended oils for summer/winter contained in the 993 owner manual can be found in the approved oils list so not sure why you would go for 0W40.
Having said that, it is true that 10W60 is not recommended in the owner manual. Not sure if maybe it was not available in 1994 or had not been tested yet? The closest i can find in the manual is the 10w50.
Cheers.
After reading recommendations by several commentators on rennlist and elsewhere, I recently switched to the non-synthetic Valvoline VR-1 Racing Oil 20w-50, with Phosphorus/Zinc of 0.13/0.14.
With so many oil experts here knowing more than the engineers at Porsche, I don't understand why PAG doesn't offer them jobs in Stuttgart - what an asset they would be.
Post #38 says, 'On the Porsche classic oil, I fully agree it is a marketing exercise to make money'.
So you know folks in the Porsche marketing department? or do you have particular evidence?
With so many oil experts here knowing more than the engineers at Porsche, I don't understand why PAG doesn't offer them jobs in Stuttgart - what an asset they would be.
Post #38 says, 'On the Porsche classic oil, I fully agree it is a marketing exercise to make money'.
So you know folks in the Porsche marketing department? or do you have particular evidence?
The issue wrt Porsche marketing is twofold
1) the refuse to make public the constituents of their oils, Most reputable oil manufacturers publish that info so that an informed consumer can make an informed choice. It reminds me of snake oil peddlers
2) they are recommending an oi that clearly is out side of the parameters set by that smae company when our cars were manufactured
When the first 993s were sold the then current spec was SH, reformulated SJ specs were issued in 1996 w/ an eye to increased fuel economy and longer cat life. Our engines didn't change it was just that the politicians took over and as ever they made some very poor decisions, we can add the ethanol mandate to the zddp reduction as poor decision from our perspective. Now at Porsche the marketers have sway. You used to be able to purchase spec books for your car, that ended in 1996 too, again the policy is, trust us we know what is best and you don't have a need to know.
03-19-2015, 05:40 PM
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