Any information you may receive related to this commentary is provided merely as friendly suggestions, not as expert opinion, testimony or advice. 
Maybe you have been a long time Porsche owner or just bought your first 986 or 996... Either way, the cost of ownership can often be more than the initial investment. Preventative maintenance is the key to avoid unexpected expenses.
With air-cooled 911 as well as 356 and 912 models commanding the highest prices ever, the 986 and 996 are excellent examples of models that can be purchased for $20,000 or less. If you haven't yet purchased a Porsche, check out Porsche Club of America's YouTube channel for these must watch segments covering buying a 986 or 996 as well as pre-purchase inspections:

With an air-cooled Porsche, maintenance is pretty simple.

 Change your oil often with high zinc oil, use fuel system cleaner regularly to keep injectors clean, and adjust your valves regularly. Obviously, there is more to ownership than these service items, but these models are bulletproof and maintenance-free. 
The water cooled Mezger engines are based on this same platform and too, in stock form in street use, are very reliable in GT3, Turbo, and GT2 models.

Likewise, the 2009 and later models based on the MA1 engine have proven to be very solid power plants. Again, regular oil changes along with regular use of fuel system cleaner ensures fueling and oiling issues do not lead to premature cylinder and piston wear. As with all direct injected, lack of injectors in the ports leads to contamination of the intake ports and left unchecked, can lead to excessive valve guide clearance due to wear.
The 986 and 996 get lots of bad press.
They are amazing cars for the money but cars that are poorly maintained can later in life have huge repair bills associated with correcting known deficiencies.

Here are the items that should be addressed when servicing your 986 and 996, including 987 and 997 models through 2008. This list includes things you should know about your engine so that you know what to look for, hopefully to reduce the likelihood of costly repairs down the road.

  • Oil: You should drop the oil pan with every oil change. It does not add much cost to an oil change but doing so lets you inspect the bottom of the oil pan for wear debris that can come from numerous sources such as chains, lifters, IMS, chain rails, and other items that wear in your engine. Monitoring these wear items as seen through the contents of the oil pan let you gauge the health of your engine. Always use the LN Engineering magnetic drain plug when changing your oil for ease of inspection for ferrous wear metals. If you do not know the history of your car and the oil comes out very dirty, or you have what appears to be noisy lifter, never, under any circumstances, use an engine flush product. It is best to do several oil and filter changes in close succession to gently clean the engine with a break in oil, like Driven BR40, before switching to a street oil like Driven DT40. Street cars should have their oil changed every 6 months or 5,000 miles with Driven DT40
  • Oil Filter:  The factory provided a cartridge style oil filter. Although environmentally friendly, many owners prefer to use the spin on oil filter adapter offered by LN Engineering. A second benefit to such a conversion is the filter is full-flow, meaning no oil can bypass the filter, ensuring better filtration than the stock filter arrangement. A bonus is the ability to add a FilterMag, which further improves oil filtration. The only spin on oil filter adapters we use in our shop are Napa Gold/Platinum or Wix filters.
  • RMS: Oil leaks around the bellhousing are commonly caused by a leaking rear main seal. Whenever you have the transmission out, always replace the rear main seal with the newest Genuine Porsche rear main seal currently available. A special tool is required to ensure the crankshaft is properly centered in the case prior to using the correct install tool to set the depth. Porsche also offers updated case perimeter bolts that have thread sealant applied to the threads and under head to stop commonly leaking bolts in this area.
  • AOS: The air oil separator processes crankcase windage (blowby) and separates the oil from the air, returning the oil to the sump. In a perfect world, the cleaned air is discharged into the intake manifold. Unfortunately, the AOS has a nasty habit of failing, causing your engine to smoke horribly. Repair requires the whole intake to be removed and cleaned of oil, then a new AOS fitted. Again, only use a Genuine Porsche AOS. Those who track their car can upgrade to a Motorsports AOS which has much better performance on the track.
  • IMS: The intermediate shaft bearing is probably the most heated topic discussed by Porsche owners. There are many options out there. We'll be biased as the LN IMS Retrofit has been offered for a decade and no other system has a proven track record, with exception of the IMS Solution which backdates the IMS to use a plain, oil fed bearing like the aircooled Mezger engine. That said, the most important thing to take away from this is the IMS bearing must be changed as a maintenance item. Ignoring it will just lead to sorrow down the road, as once the bearing starts to fail, changing it no longer is an option.
  • Tensioners: Many people don't notice when they start their cars in the morning that their chains rattle. Ignoring bad tensioners will eventually lead to a chain failure, another thing a Porsche owner never wants to experience. The fix is simple - there are three chain tensioners. One in each cylinder head and one for the IMS chain. Replace all three if you have chain noise at startup. If new tensioners do not quiet noisy chains, master link timing chains can be installed without engine disassembly to fix stretched chains.
  • Water pump: The water pump, like the IMS, is another item that is often missed. The water pump should be replaced every 4 years or 50,000 miles and again, only with a Genuine Porsche water pump. Once a water pump fails, the impeller pieces will lodge themselves in the cylinder heads and will cause cracked heads later on down the road. At the same time, a Genuine LN Engineering 160F low temperature thermostat should be employed with Genuine Porsche coolant. We also recommend adding Driven CSP to the cooling system for added corrosion protection and improved lubrication for the water pump. Cars that are driven hard or tracked can benefit from a 3rd radiator or upgraded CSF aluminum radiators.
  • Chain rails: The main chain rails cannot be changed, however on the early 5-chain engines, the vario-cam wear pads, which there are two per cylinder head, are wear items that need to be serviced. If cam timing deviation is over 6 degrees, they for sure need to be replaced. Although driving habits will greatly affect the longevity of these parts, a common number thrown out is 60,000 miles for these. Porsche again has redesigned these pieces and the newer ones are much longer lasting, so you might consider changing them along with the 4th and 5th chains.
  • Clutch/DMF: The dual mass flywheel is another item that often owners want to upgrade with a lightweight flywheel or racing clutch. However, the dual mass flywheel provides protection in form of dampening harmonics and should never be replaced with a lightweight single mass flywheel unless additional steps are taken to prevent crankshaft failures. The factory clutch has also been proven to handle significant increases in HP without slipping, so heavier pressure plates and higher friction clutch compounds are not needed. The dual mass flywheel and clutch should always be replaced when doing an IMS.
  • Spark plugs/Coils: Misfires can be caused by a bad dual mass flywheel, however, more commonly it is bad ignition coils and spark plugs that are the culprit. We recommend using Genuine or OEM spark plugs and coils and they should be replaced if there is any sort of cracking or carbon traces on the coil. When replacing one, replace them all. Lastly, the spark plug tubes on a 5 chain engine should also be resealed when changing spark plugs.
  • Injectors: With modern ethanol fuels, we are coming across more and more failing injectors that cause poor fuel atomization, dribbling, or poor flow. All lead to fuel washdown and rich operation. Regular use of Driven Injector Defender or for cars needing a serious cleaning due to poor maintenance or bad operation, Lubro Moly Jectron is the cleaner of choice. If you keep driving an engine with bad injectors, you will end up loosing cylinders. It is our most current hypothesis that bad injectors are the leading culprit behind scored cylinders common to modern engines, further contributed to by high operating temperature and long oil drain intervals. Monitoring fuel trim values are a good way to ensure that your engine is operating correctly - trim values should be around 1.0. And always use premium fuel from a Top Tier fuel manufacturer.
  • Lifters: The M96 and M97 engine is known for having lifter issues in engines that have been poorly serviced due to clogged oil passages in the lifters themselves. Again, poor oil change habits and contaminants in the oil can also lead to excessive clearance between the lifter and lifter valleys. It is common to do a lifter job replacing the valley and all the lifters when they are noisy, but before doing a lifter job, it's essential to make sure you do not have a cylinder failure in progress. Most commonly, a failing cylinder is misdiagnosed as bad lifters. Again, do not use any type of engine flush product to try to bring lifters back to life. You will end up causing damage to other oil pressure driven components in the engine.
  • Cylinders: There are three kinds of cylinder failures. Slipped sleeve was limited to the 2.5 Boxster and is not a failure we see very often any more, except in very low mileage cars. D-chunks and cracked cylinders can occur with any of these engines but are most prevalent with the 3.4 engine. The last, and most common, are scored bores, and this is most prevalent in the 3.6 and 3.8 models. There are many hypotheses as to what causes scored bores, but like mentioned above, we believe it's from over-fueling, piston skirt coating wearing or flaking off the pistons, poor oil service history, and high engine operating temperatures. There is not much you can do here other than change your oil frequently with a high zinc oil, using fuel system cleaner regularly, and also use a low temperature thermostat to control engine temperature. It is possible to check for early signs of cylinder scoring while the engine sump is removed, using a bore scope to sneak up into the bore behind the piston, while the piston is at top dead center.
  • Track: Cars driven on track, even street cars, should have their oil changed after every event with a true race oil like Driven XP9 and should be fitted with an LN Engineering 2 quart deep sump to prevent oil starvation. If you drive your car on the street, install a matching skid plate from LN to protect your sump. The AOS should also be upgraded to the Motorsports version. If you don't already have a low temperature thermostat, install one, and consider upgrading your radiators as mentioned above. Brakes are a critical item overlooked - brake fluid should be upgraded to Motul RBF660 or equivalent and flushed before every event. This is an incomplete list of things to check or upgrade - be sure to have your entire car fully inspected to ensure that it's track worthy before putting yourself, your car, and others in danger.
There are many other systems in your Porsche like filters and belts that also need to be serviced, but knowledge of what to look for and when these items need to be changed is universal. Any competent mechanic will have basic knowledge of vehicle systems to know what to do with commonly serviceable components on your Porsche vehicle.

In conclusion, when servicing your Porsche, be sure to use a facility that specializes in the model that you own. This is especially the case with the newer water-cooled models, where a misdiagnosis can lead to needless repairs, or worst yet, where preventative maintenance is neglected, leading to a preventable failure that require complete engine overhaul.

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