Mileage and Such

I am now at 206k. I had an oil analysis at last change. I am due for next change at 209k and plan to have it analyzed again by same mechanic for comparison. (I need to go back and look, but some levels were a little high). The crisis this time around was that my catalytic converters were worn out and needed replacing so I could pass emissions and drive in Atlanta. Otherwise, car drives well. The mechanics who have seen it post here and are free to chime in. The car is kinda "... broken in" after all these years and no garage queen, but a nice little driver that is kinda coming into it's own. Questions... Who has gone this far in a 996? Who has tracked oil analyses over time? I can post my last results when I find them. Who wants to take the Pepsi Challenge on 996 mileage? Anyone had a high mileage failure? Pattern seems to be lower mileage cars that get hit at about 80k or below. Answers to questions you may ask... I've had clutches and rear main seals and IMSB done. Otherwise, maintenance. Drive the car daily. Some would say too gently because I typically shift below 4k and drive it more like a V-8 than I probably should. Two last questions... I had the catalytic converters replaced with FabSpeed's... Because Porsche charges an arm and a leg for theirs. Car now feels more "... jerky" or bucks or more responsive... I am guessing that is less back pressure that would otherwise even out the smoothness of the engine? Also, mileage seems to have gone down slightly. The car is slightly louder and maybe I am on the gas pedal harder these days. Anybody replaced their converters with FabSpeed's and had similar issues? (I had an RX-7 in high school/college and after I replaced the exhaust with headers and free flow, it took longer to warm up and ran a little more "... high strung" if that makes sense). Caveat, I understand cars and understand basic mechanics... I am no gear head. I expect that applies to most of us. So please "... dumb down" any replies accordingly. Thanks and hope everyone is otherwise enjoying their 996. (I really think these things are getting better looking every day). JKC

I think Macster has a Boxster with about the same number of miles but I haven't heard of a 996 with that many. I'm at 133k right so now I have way to go. As for your cats, I noticed the same thing too when I replaced mine. You have to give it more gas when starting off and it will get jerky if you don't. Embarrassingly enough I've even stalled the car a few times because I forget how different the driving characteristics are with it now. Also the jump I feel at 3300 RPM when the variocam kicks in is more pronounced. Other than that though I love the Fabspeed cats - they are a better deal than factory if you don't mind these changes in driving behavior.

Glad to hear your experience is similar to mine. Frankly, the change in behavior is mildly irritating... But I guess I can give Porsche my first born male child if I want to switch back. From your PICs it looks like you track your car or do sport events... I don't. So, a smoother riding car is preferred. Am I getting old? In any event, thanks for the reply. Any notice in mileage changes? I used to average about 26 MPG. I've been checking it is now ranging from high teens to low 20's. (That considers highway miles and city driving blended. I have not really put pen to paper to get a finer point on it). JKC

for the thread, for driving the car, and for positing this. We need more people with high mileage cars, by that I mean 180k+ to start posting here. I got mine at 117k in July, she is now at 122k. Mileage exceeded my expectations as well. Car enjoys cruising on the highway. At 75-80 it gets 27-30MPG. At 90-95MPH it gets 25MPG. I really enjoy driving it around.

The jerkyness could be attributed to the car being more responsive now and your car is likely making significantly more power since you had failing cats. But you're on a stock tune, so the powerband is not going to be linear with aftermarket parts and no new tune, so you feel the power differences. Aftermarket cats will be louder than OEM.

Generally I always recommend an ECU tune if you are either doing cat bypass or high flow 200 cell cats. In my experience, I've always seen somewhat of a power loss or a shift in the powerband when high flow cats or cat bypass are installed.

273K miles in my 02 Boxster. Only had one oil analysis done early on -- before the first oil change -- and based on the amount of water in the oil concluded 15K mile oil changes was nonsense given how cold blooded these engines are. Dropped that down to 5K miles and changed the filter too at the same time (factory had the oil filter change interval at 30K miles!). The car is on its original converters but one is weak and every so often -- in cooler weather -- trips the CEL. As long as the engine runs ok and it can pass smog I'm leaving it alone. The factory converters are easy $1K for the hardware and maybe 2 hours labor for at least $1300 for just one side but at this high miles I'd probably replace both sides to keep things as close to identical as possible. In the meantime I'd heading for 300K miles.

I feel like my C4S is just getting broken-in at 127K miles!

I am at 134K and plan on getting my oil analyzed after my next oil change

Macster, That is awesome. Have you had to replace chain sliders or rebuild the top end? Thanks, Ray

Macster, It appears I've thrown down the gauntlet too soon... Awesome to hear on your mileage. Other posters... Are you saying I should have my computer adjusted or "... flashed" as a result of cats? Again, this is a little beyond me and I only got the cats to pass emissions... Not to speed up... Thanks JKC

I have my last three... but I am at only 81K which seems hardly used at this point.

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Only internal engine work was the passenger side VarioCam solenoid and actuator went bad. The chain guides/rails were fine. The actuator's internals were bad. Before he opened up the camshaft cover I asked the tech about replacing the other side to renew the guides/rails and he said we'd wait to see what they looked like on the bad one. They looked just fine. No real wear on the plastic rail covers, so the tech said to leave the other side in service until it acted up and required replacement. Rebuild the top end? Nah. The top end's fine. So's engine. The clutch might not make 300K miles though. Cheap factory clutches.

I rebuilt the engine in my last 996 Carrera (MK2) at ~170k miles. It was driven hard though I'd only owned it for about 9 months/20k miles before oil pressure got very low. I found a damaged rod bearing and significant wear on the remaining 5, though everything else was fine. I refreshed the engine. Most parts in there still looked great, I changed a few tensioner pads, all the lower bearings, valve job and put it back together. That car needed a cat as well around the same time - I used a new factory cat. I'm really not a fan of aftermarket pieces when possible. I've replaced several vario cam actuators on the 3.4 motors as well.