How does bore scoring start?

How does bore scoring start? The recommendations in the owner's manual says to a avoid engine speeds above roughly 4,200 rpm during the first 5 minutes after startup and not to let the engine idle. Other recommendations are: Drive the car at least 20-30 minutes when possible. Let oil temperature fully stabilize. Avoid repeated 2-5 minute trips. I already will go for a 10 minute drive when I pull the car out of the garage to be washed. Do the same thing when I am done washing the car. I had the car idle for 10 minutes while I was topping off the AC. Do these single, rare events trigger bore scoring? I have no idea how this would trigger bore scoring. So I started wondering if bore scoring is a one time event or an ongoing trigger? Realistically, 90% of my car trips in any car is less then 30 minutes. So, I use the 996 rarely due to all the recommendations about heat cycles, So, is bore scoring a one time event or an ongoing combination of short trips, old oil etc?

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Ok here's my guesstimate. Not saying this is 100% correct, but maybe at the least, partially correct... Lokasil cylinder material fails, the resin binder holding the microscopic silicon particles in the aluminum matrix fracture under thermal, mechanical, oil breakdown stress, causing the silicon particles to dislodge out of surface substrate. This migration further destroys the cylinder's protective 'film' of oil, leading to catastrophic, rapid wear. Once piston ferrous coating wears off, its aluminum-on-aluminum wear. Increasing piston slap/OOR/Taper/cyl oil clearance. Giving a good start for Piston Rock. When the piston moves up and down and switches direction at the bottom, the piston skirt rocks and creates immense friction.This can lead to a snowballing of more and more wear/scoring. Like all the above wasn't enough... the 996 engine sports an open-deck design where cylinder banks are unsupported. Cylinders 4, 5, and 6 run slightly hotter, which can along with some of or all of the above to creating/accelerating scored cylinders. jmo

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This makes the Slakker/Hartech closed-deck upgrade seem that much more appealing. Is the Mezger M96 also an open-deck design?

Mezger uses individual replaceable cylinder liners fitted into a water cooling housing so it is not really comparable with a standard block casting of any type. More closely resembles an aero engine like an O-540 or even a VW beetle engine, which it is distantly related to.

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The change in cylinder surfacing material removes the sensitivity.

There are a great many contributing factors to bore scoring, but what actually starts bore scoring is quite simple. Porsche uses the same pistons on both banks. This means the crank pin offset is correct for one side of the engine, and opposite (increases moment of inertia at BDC) on the other bank, 4, 5, and 6. The rod ratio in these engines is 1.73:1, which is just too short. The Boxster has a rod ratio of 1.75:1, which is why Boxster bore scoring is significantly rarer. The rocking motion at Bottom Dead Center created by these two factors damages the cast iron skirting on the pistons, which eventually fails. If a car is not driven every day, and or the injectors start to wear, fuel dribbles out the injectors when the engine is shut off, removing the tribofilm created by the aluminum/silicon engine block. There is far more to bore scoring, but this is how it starts. For the cast iron skirting, Mk1s use ferrostan, whereas mk2s use ferroprint. Ferroprint is a much weaker bonding process that makes mk2s more susceptible.

I seen your other questions on your post, and to summarize it best, bore scoring is nearly 1:1 analogous to cancer. Bad heat cycle management, bad oil, and bad injectors is the equivalent of smoking or drinking or any other carcinogenic behavior. Once bore scoring starts, it's like having a confirmed case of cancer. Living a healthy life and taking the proper meds (FIMP cycle) will stave off further stage cancer for a very long time. At some point, surgery will need to be performed. Unfortunately, these cars don't have the 1% chance to cure its own cancer like the human body does. In the case of these cars, gently heat the oil up, drive the car like you stole it, as frequently as possible, use top tier fuel to keep new injectors new (replace your old ones if you haven't already), and use a high quality oil and change it every 6 months. Avoid cold climates where possible.

I see you live in the Great White North, do you drive year round ?

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It's a toy car. Never Winter driven. Driven April to October. Maybe 1000 miles annually. Typically used for planned drives. But, I do like to use it to go out for dinner sometimes. Car has 50000 miles. Scoped at 45000 miles. No scoring. Has had all the usual updates under my ownership: IMS Solution, clutch/flywheel/RMS, AOS, Water Pump, Thermostat, Engine Mounts, Coolant Tank. Annual oil changes 5W50. Car is not started for 6 months during winter storage on a lift in my regular garage. Essentially, my car is babied, used very little. Hope to use it much more as retirement approaches. But I will say I use it less than I could due to all the concerns of short trips etc.

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Goodness me your car is in gorgeous shape. Was this scoped from the sparks or the sump? Scoping from the sparks is essentially useless. Scoring starts at BDC, where the piston will block view from the top. The only way to see early stages of scoring is from the sump. If you can see it from the sparks, to use my cancer analogy again, it's already at stage 2. There will usually be many other symptoms at this point. Bore scoring doesn't punish you for simply driving the car, so drive the crap out of it, as long as you are following best practices. Provided your injectors are new, not driving the car for more than 48 hours actually contributes to bore scoring. If your injectors are worn, there isn't much you can do to prevent the wash down of the cylinder walls. With all other factors being equal, the car injector issue is something that can be lived with, and is much less impactful than proper driving procedures. Enjoy your car more, these are pretty reliable cars all things considered.

Sure helps to... 1. Run great high viscosity and high moly oil. 2. Keep it fresh by changing it often (2x year) to retain its lubrication qualities. 3. make sure your fuel injectors are working properly and not leaking. 4. Warm the car up properly and then get it good and hot by driving it like you mean it to burn off the moisture in the oil. 5. Don't drive like a little old lady worried about gas mileage. Instead, take it thru it rev ranges. Too high a gear at too low rpms will only facilitate piston/cylinder problems. But what many do instead is... 1. Run crappy oil with low moly and low viscosity to save money. 2. Change oil at very long intervals to save money. 3. Don't keep their fuel injectors fresh and in good working order to save money. 4. Don't drive the car and instead let it sit to save money. 5. When they do drive the car, they drive like a little old lady at low rpm to save money on fuel and mistakenly think they are protecting the engine. The moral of the story is to spend a couple of bucks on the 996 and drive it like you mean it. Your bores will thank you.

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I'm doing all of the good things and my Use Oil Analysis numbers from Speed Diagnostics look fabulous. Bore scoring is good to know about but I'm not losing any sleep about it. I went on a group drive with my Porsche buddies last Saturday. The other 996 and I were the only ones with air conditioning. I had no issues staying glued to fender of a hopped up 1979 911SC in spirited driving. And my car as nary of speck of rust, anywhere. One 1972 owner said his car had never been driven in the rain and it certainly looked like it. All of those air cooled guys are highly focused on the R word. I'd rather repair bore score some other 996 issue than sending my car in for a chemical dip and the metal work that goes with fixing a body that looks something like Gouda cheese: You Tube Some of the gaping holes in this body were pushing Swiss cheese grade. FlatSix, LN and others offer us an array of bolt up solutions. Is the air con too cold? Allow me to adjust it to your liking. lol

Bore-Scoring is probably one of the BEST " Catastrophic Failure" one can have on the M96/7 engines... 1 .It doesn't knock a hole in the block 2. It doesn't destroy a $6k crankshaft 3. it doesn't bend a rod 4. it doesnt break the camshafts.. 5. It doesn't damage the heads 6. It has a proven repair that is more robust 7. It comes on very slow and gives plenty of time to let you get your affairs in order.....lol So if you are going to roll the dice and take chances with the your engine and mistreat it.....Bore-Scoring is the Catastrophic Failure you want to have ....lol...

Lol, that's a fresh perspective to have.

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I do love watching the chemical dipping on YouTube. But glad as hell i have a 996 versus an older model. Great to hear you are a fellow 996 enthusiast. Seems that every day we convert a few more!

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I think this is very insightful. My biggest concern, is that my car really is a garage queen as I don't really have the opportunity to drive it as often as I would like, but retirement will be here soon! To that end, car was scoped through spark plug holes as part of the PPI. Then was scoped a month later from the sump when the IMS solution was installed. I've been using 5W40 oil up to this season. this year, I wanted to 5W50. I grew up with Dad's advice: always buy Michelin Tires and Castrol Oil. So the car runs on Castrol Edge 5W50. I'm now rethinking this - Driven is just soooo expensive especially in Canada. I compared the VOA for Edge vs LiquiMoly. VOA's are very close. Next year, I think I'll go to Motul 5W50. I only change the oil annually due to the low mileage annually - always in spring. Car is shut off in November, and only restarted in April with a fresh oil change. Time to stop worrying about it. Just drive the blasted thing when I get chance

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My car will also be stored from Nov-Apr due to climate. My plan was to change the oil right before hibernation, but now second guessing myself. Is there a best practice for this?

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Every comment I hear recommends changing the oil prior to storage. With the fact that I only put on 1000 miles per year, I suspect that there is very little contamination in the oil. I park my car on a lift. So, in the spring, I dump the 1 year, 1000 mile oil, and put in brand new oil. Filter too. My only rationale on this is that I like the feeling for my first start up of the year, it is completely brand new oil that has not sat over the winter. The car is never started in the winter. This is what I do. Not sure it is correct. I've posted about this here before too. The recommendation is every 6 months. So, in my case, I would change it in October, start it once, maybe go around the block. Then change it again in spring. That is not just wasteful, but makes no sense to me.

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My understanding of changing before storage is to make sure you have the least contaminated oil in the engine. No extra combustion residuals, no fuel, no water. But with so few miles, I'm not sure the first 2 would be an issue. The most likely issue from water from condensation throughout the year. Agreed 2X per year is wasteful at 1K miles per year. Maybe the only thing to change is when you do it. I would bet you have a bigger risk from fuel going bad than the oil causing a problem. The problem is lack of data. How many people do you know that have a bad engine from not changing the oil before storage? Or how much the wear has increased? Sorry, more blather...

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Hartech in the UK released a technical document covering the 4 major failures applicable to the M96/97 engines, it's a long read but well worth it for curious owners. You can download it here: Common Porsche Engine Faults - Hartech https://share.google/1NnfdrmNfUQk4R6Vh

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I've read other Hartech articles. That was a long one - 174 pages. Very good read. Thanks gbarron

When a mommy piston skirt and a daddy cylinder bore love each other very much�

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Bore scoring isn't something that happens all at once and there are many contributing factors. For a deep dive, I recommend reading the paper I published in 2019: https://lnengineering.com/free-downl...arles-navarro/ It took me over a year and I purchased and read dozens of SAE and other research papers to wrap my head around all the root causes. To oversimplify things, there are two main factors: 1. Enough silicon particles fracture that there is no longer the necessary oil film to support piston and ring function. 2. The piston skirt coating fails and allows for two aluminum surfaces sliding against each other. If you distill all the contributing factors to one thing, I'd say cylinder bore washdown due to over-fuelling or poor fuel spray. Like I said, this is an oversimplification.

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My 2024 Subaru has a factory oil temperature display. Clearly, on a summers day, it takes a good 20 minutes for the oil to get up to operating temperature.(96 to 99 degrees Celsius). The water temp gauge show normal within 10 minutes. Similarly, in the 996, water temp gets to normal within about 10 minutes. Since I have on oil temp gauge, I imagine similar to the Subaru, at least 20 minutes to get to normal oil temperature. In the end, I'm 58 years old. At my current rate of mileage, I may get to 100K in 30 years at 2000 miles/year. I think I have to stop the doom and gloom scenarios and just use the car. Better a 10 minute drive than no drive.....

10 min drives are fine even if that is all you ever do ...That's about all I have done for the past year since the Health Issues... Just use high quality oil and change it OFTEN !!! . It will get a lot of water and fuel in the oil from so many short drives..... ( Do a Used OIl Analysis to see how much ...)

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Oil gets combustion byproducts in it during normal operation. Oil can still look "clean" and be contaminated. These byproducts interact with moisture in the crankcase, forming acids. What you can't see is that this can cause corrosive wear, especially on bearings. That alone is enough reason for us to recommend changing the oil in the fall, before putting a car into storage for the season. That's great that you don't start it to idle it. That's the biggest mistake many make thinking it's important to circulate the oil to protect the engine.

Way too many people declare that they are good owners because they start their cars and idle them for a few minutes every month and think that it's a good thing. Then there are the truck owners who use remote starts and idle their cold engines for 20-30 minutes every day. Some of these same gents/boys don't even shut down to fuel or realize that their rigs have an off switch at all.

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In the latest 11 After 9 Podcast, Derek had Lake Speed Jr. on there. As expected, the topic of bore scoring came up. They addressed the above and lots of other points, heavy on facts, not opinions: You Tube