dip stick vs dash gauge

here is how I check my oil level, engine is warmed up and car parked for 20 minutes on level ground. the dash gauge is reading three bars (so only one bar above low minimum). Dip stick is on the upper half between two dots on the dip stick. can the dash gauges loose accuracy somehow? Prior owner used 15w-50 mobil 1 on the car, it was a southern ride. I changed the oil to 5w-40. Is it using oil? It does not smoke or drip. Thank you

I get the best correlation between stick and gauge first thing in AM, after sitting all night, before starting. You ask "Is it using oil?" Are you adding oil often? If not, no. If so, yes. Typically these engines will go 3k + miles before needing to add a quart. Porsche specs something silly like 800 miles per quart. Maybe if your commute is 25 miles each way in the left lane of the Autobahn everyday. Not so much in USA. PS: Rock breaks scissors, Scissors cut paper Paper covers rock Stick trumps gauge.

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Brilliant. Thats what I think, sticks trump gauge. It is just odd how the inaccuracy of the gauge seems to have started after I changed the cars oil diet. Oh well I will keep an eye on the stick regularly. Love this car! With all the belly aching about 996 we dont spend enough time posting the good stuff here. Took a ride in the mountains with bunch of other POrsches over the weekend. Three hours of twisties with my 5 year old son. What a great saturday chasing a 997 convertible and 993 c4s.

The design of the gauge is inherently prone to not being totally accurate. It's basically a stick with wire wrapped around it going into the sump. It measures the oil level by reading the electrical resistance on the wire. So, it seems perfectly reasonable that the 15-50 oil could cause it to read higher since it's thicker and could have been coating the sensor better than the 5-40.

Somewhat related to this topic, any time I refuel and restart the engine, the oil level display keeps showing half-full. A subsequent stick check always proves that display info completely wrong. I believe the only time the display oil check can have some semblance of credibility is prior to a 1st start in the morning as fpb111 rightfully points out above.

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We'll not know for sure since I do not have the electrical engineering background nor can I call upon somewhere here to go over this with me, but I would hazard a guess the effect 15w-50 oil has on the wire's resistance vs. some other oil from any coating of the bare wire above the level is insignificant. I bought a sensor and cut it apart and the bare wire is only 1.5" long and doubled that is it is in a loop so the wires are held secure and can't move about. The wire is only intended to measure the uppermost 1.5l or so of oil. The wire is very fine too -- 0.003" in diameter -- and any coating of oil I would have to believe can't affect the reading obtained to any degree that matters.

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The proper way to check the oil level is to drain the oil according to the steps laid out in the factory shop manual, add the specified amount of oil (also in the shop manual or from a TSB or some other document) to the engine measuring/metering this amount out using the readout from the oil dispensing gun then using the dipstick and the oil e-level system to confirm they display/indicate the correct oil level based on the known amount of oil added to the engine. I have spoken with some techs about the oil e-level system and how it can fail and how often, and I was told failures of this are rare. One tech remembered replacing one under warranty. The failure mode was no reading. I assume in this case the wire broke. (It is a very fine wire: 0.003" but appears to be made of a pretty exotic metal and is probably really robust and resistance to breaking.) Based on my taking one apart I would believe a wildly variable or varying reading is also a possibility the wire comes loose and thus moving about possibly shortening, if the wires of the loop make contact, the distance through which resistance is measured. There might be some reality filter in the DME if the reading is too far out of spec if the reading varies too much in too short a time, is not stable (at least for those engines that the oil level is measured with the engine running), the reading will be discarded and no reading displayed at the dash. This lets the driver know the system is not working and needs attention. As for oil consumption it is very possible the engine used some oil from the hard driving -- 3 hours worth -- you subjected the engine to. If so this is no reason to worry. What is also a possibility is the oil consumption has been ongoing for some time but the level kept the same by the build up/accumulation of unburned gasoline and water, mostly water. Then you take the car out and drive it hard, get the engine and engine oil hot hot hot and keep it hot for a while (3 hours) and this unburned gas and water boil away and the level drops. Suddenly. And this looks like an oil consumption issue. It is but the real consumption is spread out over time. Yet another possible explanation is given the usage for the 3 hours of hard driving the AOS was overwhelmed with oil vapor and passed way too much of this along with other crankcase fumes to the engine. The engine has an oil consumption problem but it is not through the traditional means oil is consumed but via an under-performing AOS. Regardless, you do not have any reliable data to pass judgement on oil consumption at this time. You have changed oils. I suspect the oil consumption will not change. Hot 15w-50 and 5w-40 are not that far apart. (15w-50 is not an approved oil. how knows how it works in these engines? In fact it may aerate/foam more and this may contribute to overwhelming the AOS and actually cause more oil consumption that is thicker viscosity might lead one to believe would result in lower oil consumption.) Relax. Be sure you learn to accurately measure the oil and get a consistent reading. The levelness of the car plays a role as does how hot the engine and hot the oil got (oil temp can lag behind coolant temp) and how long the engine sat off before you check the level. Keep accurate records of the oil level and record how much oil you have to add and after how many miles. My guess is you'll tire of this exercise because you will not see any significant oil consumption and get bored worrying about nothing.

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^ This...I think this is an overlooked fact that can play a big part in how the gauge reads. If your car were burning an excessive amount you would probably see deposits on your tailpipes and rear bumper with associated smoke while driving Thankfully we still have an actual dipstick. While trying to reset my key fob memory (still no luck) I was cycling the key multiple times. Without starting or moving the car the readings would vary between 4-5 bars

As Macster said, I always thought, and pretty sure I read it somewhere, that the gauge does not cover the full Low-High marks that the dipstick does, but just more accurately the top of the level. The only time "full" level matches in my car is when it sits for like 24 hours. Checking the oil hot, always shows a lower level in both the gauge and the stick, I assume from captured oil. If you pull the sump plate oil will drain for many days. But a really significant amount over like 3 hours. I will hate when all cars have no dipstick.

Macster- I am always amazed by your fact and science driven support of RL, thank you. The engineer in you shines through your posts. One point of clarification-- the mismatched readings between the dipstick and e gauge started before the three hour drive. My car is a daily driver. It is never abused and always enjoyed I do keep revs higher than 3k but never sustained high revs. It is maintained according to and exceeding the factory manual. I will do the drain and fill ahead of scheduled oil change during clutch/rms/IMS/aos replacement next month. Thank you all.

the in-dash oil level indicator only covers a quart from bottom to top of the range. So if you add about a quart when the display is blinking, it'll read full. I use the dipstick and 2 days of track will yield about a quart and a half of usage. Regular street usage for me is about a quart per thousand to 1500 miles. I don't drive it like i'm pampering a collectable rolls royce motorcar. It's driven more like a subservient little bitch that I dominate

My dipstick and e-gauge always match pretty well when measured in the morning. Also, per owner manual, they are supposed to match too. Why you guys think they are not supposed to match? From my '03 owner manual: E-gauge : "The difference between the min and max marks on the segment display is approx. 1.25 litres . One segment of the display corresponds to a quantity of approx 0.2 litre." Dipstick: "The difference between the two marks [the min and max on the dipstick] is approximately 1.25 liters "