997.2. Oil use - Page 1 - 911/Carrera GT - PistonHeads UK

How much oil is used in normal driving?

None.

Or up to one litre per 600 miles if you ask an OPC.

Why do you ask? In the meantime, I can tell you it varies, As one poster correctly noted the owners manual gives 1l per 1000km for the highest acceptable consumption. I would offer the opinion while this may be acceptable to Porsche but it would be quite unacceptable to me. That's a lot of oil being consumed. Some engines, most engines thankfully, use less than that. I do not recall how much oil my 02 Boxster used when new -- it wasn't much though or I'd remember it -- but I can tell you with over 285K miles it uses a bit over 1l (1 quart) in 5K miles. A mix of city and highway driving with no track time. I do not suscribe to the belief the oil seeps past the rings into the cylinders. I have posted before why I do not believe this happens and I won't make this post any longer to post this again. But I will take the time to state it is a theory of mine the majority of oil these engines consume arises from the lousy AOS (air/oil separator). We have all observed the cloud of oil smoke at cold engine start. This comes from the time the engine was running before this start the AOS failing to remove oil vapor from the crankcase fumes. These fumes then deposit this oil vapor in the form of oil droplets on the intake manifold. If the engine is shut off this oil runs down and upon the next cold engine start this oil is ingested by the engine and burned but burned incompletely because the engine and converters are cold and the smoking is the result. Now if this oil collects and the engine is not shut off it is still consumed but there is no smoking. But this is oil consumption, nonetheless. This passing of some oil vapor through the AOS to the intake occurs all the time the engine is running. Those engines that appear to use a lot of oil I suspect have a particularly lousy AOS rather than a bad ring/cylinder seal or bad valve seals, the usual places through which oil that gets into the chambers gets into the chambers.

anonymous said: [redacted] so in normal driving that's really none ;-) most cars now days don't need oil even inbetween the 20k services either of Mine uses less than 1/2 a litre inbetween 20k/2 year service so yes while that is some, in normal driving week to week that's as good as none. and that's prob just the smoke on the odd start up Porsche style. normal driving I still say the car should not be using any which is measurable. other wise 1/2 the cars on the road would fail (ie female owned ones)

My experience of the DFI engine is similar - the oil consumption sits somewhere between none and so-little-it's-very-hard-to-quantify. I typically only have to put in half a litre between oil changes (done every 8-9,000 miles). The oil consumption (or lack of it) also doesn't seem to be affected by how the car's driven. Edited by Ian_UK1 on Monday 29th September 10:35

anonymous said: [redacted]

My DFI engine (C2) is just around halfway up the scale - probably half a litre every 1000 miles or so... It runs fine. I reckon I've changed the oil every time it goes in for a service!

Thank you for the responses. The reason I asked was the consumption has been from the full to 1/3 in just 650miles, both taken from the electronic dip stick. Mixed driving and symptoms ie no smoke on start up etc. It seems a lot, depending of course on the number of litres this equates to.

IMac said: Thank you for the responses. The reason I asked was the consumption has been from the full to 1/3 in just 650miles, both taken from the electronic dip stick. Mixed driving and symptoms ie no smoke on start up etc. It seems a lot, depending of course on the number of litres this equates to. That sounds like an awful lot. Each segment is 400ml. My 997.1 uses about 800ml per 10000 miles.

IMac said: Thank you for the responses. The reason I asked was the consumption has been from the full to 1/3 in just 650miles, both taken from the electronic dip stick. Mixed driving and symptoms ie no smoke on start up etc. It seems a lot, depending of course on the number of litres this equates to. Is this a new car or a used car? A new engine can use oil as it breaks in. Generally the engine will use less oil eventually though it can take some time. More than one owner has reported oil consumption only drops off some time after the nominal break in miles. (Lab and field tests by automakers have found break in can continue for thousands of miles after nominal break miles.) There is another thing to consider. The car is driven about used for short trips. The engine never gets fully warmed up or if it does it doesn't remain that way for very long. What can happen is unburned fuel and water -- mostly water -- accumulates in the oil. This build up of fluid then compensates for any oil that is lost. The oil level then appears to be quite stable. Then the owner takes a long drive. The engine gets fully warmed up, and remains in this state for sometimes an hour or more. This then boils out the unburned fuel and water and the oil level drops as a result. The next time the driver checks the oil level it is down and it looks like it came down all the sudden. Well, it did and it didn't. (BTW, do not dismiss this. I had the oil analyzed in my recently purchased Boxster -- back in 2002 -- and the water content was 7%. That's about 0.6l of water in 9l+ of oil. This prompted me to change the oil/filter much more often than the 15K miles Porsche called for.) I have to wonder about how good is your measurement of the oil level. I know you are using the electronic oil level system but unless one is aware of the gotchas this can deliver the wrong info. Assuming you can check the oil level cold the best time to check the level then is after the car and engine have sat overnight unused. When you check the oil level the car itself should be level. If where you park the car isn't level then you will have to determine what the difference is. One way is to check the oil level with the car sitting on a level bit of ground. Then you can know when you check the level on unlevel ground what the difference is. Or back the car into its usual parking space and check the oil level as you normally would. Over time -- a short time -- I developed a feel for how much out of level parking spots affected the oil level. What I also learned, this took more time since this a rarer case -- is how much the car being parked with one side or the other side down slope, such as would be the case parking the car on street with a serious crown. My experience is -- like parking in front the library in the town where I live -- the side slope is so severe it can trigger a low oil warning from the e-oil level system even though I know the level is ok. Even more subtle things can affect the level. If you shut off the engine before it was fully up to temperature, even if when you return to the car and the count down timer has just 5 seconds showing, my experience is the reading will read lower than it would had the engine been fully up to temperature before it was shut off and the wait time before the oil level was checked was the same. In short there are 2 times I'll check the oil level. 1) After the car has sat overnight or all day. However, I do take into account if the day before if I didn't get the engine fully up to temperature. Given how I use my cars this is a rare event but I still take it into account. 2) After the car has sat some time with the engine off after having been fully warmed up. This generally occurs when I get into the car to go home after work. But another time when these conditions are true is when I"m on the road and I pull in to fill up the fuel tank. After fueling is over with I check the oil level. This delivers reliable and consistent readings as the engine was fully warmed up, the engine sat long enough (and it sits about the same time every time as the time it takes to refuel is about the same), and the station apron is level. Keep in mind that the level can read higher when the level is checked after having just shut off a hot engine compared to checking the level after the hot engine has been off long enough it has cooled down to ambient. The chances are your engine is fine in the oil consumption department and you are just scaring yourself -- you would not be the first owner to do this -- into believing the oil consumption is bad when it is not bad. You really have to be sure you check the oil level in a relaible, consistent way, every time, so you can know what the oil consumption is.