GMs Disappearing Oil Dipsticks
GM recently announced the newest generation of V8s for their 2027 model year trucks and SUVs. An announcement was made that dipsticks would be replaced with the oil level sensor only. Social and traditional media is awash with anger, not necessarily surprise, but rather impassioned screes about how OEMs are purposefully eliminating consumers ability to maintain their own vehicles. I, even as a shop owner and ‘enthusiast’, have been fairly neutral about the right-to-repair debate. OEMs should not be locking service information and data behind a paywall that is virtually unscalable for normal people. However, the idea that if right-to-repair was instantiated into law tomorrow and millions more would be working on their own cars seems to be a bit of a stretch.
There is no debating: recent design decisions have made servicing their vehicles difficult in quite a few respects. Do I think these decisions are a coordinated effort to enact something malicious? Not particularly–even with this very odd approach by the GM Powertrain team. But, there are certainly incentive structures which reinforce short term decision-making which negatively impact customers. Our more in-depth coverage of this issue can be seen below:
While GM and other OEMs will certainly get flack for deleting the dipstick, consumers will likely be unwilling to punish them with purchasing another vehicle. Who does get squeezed? The technicians charged with working on these machines. This particular article will be about how these oil level sensors might work, the software and hardware behind them, how they might fail, and impacts to serviceability.
Oil Level Sensor Systems
How do oil level sensors work exactly? A few different kinds are employed that all have different designs and considerations: mechanical/magnetic, capacitive, ultrasonic, and conductive
Mechanical + Magnetic
A mechanical sensor is one which is made up of a cable, float, magnet, and a switch. Sometimes, these sensors can be augmented with other sensors for pressure and temperature to get additional data.
Essentially, the float contains a magnet that moves up and down with the level of the oil. A cable maintains the position of the float relative to a switch which has another magnet. The position of this switch is flipped when the magnets touch. Once the switch is flipped, a signal can be sent to a module which then can show the critical level on a display. These are very simple, economical systems that are useful for alerting oil levels at their most critical. A key drawback, however, is that the oil level has to drop significantly before a user notices–usually causing damage before a low oil critical level is detected.
Likewise, the control logic remains also very simple. A module like the Engine Control Module gets a message and broadcasts it back over the CAN BUS for a device (like the infotainment) for displaying the estimated level. It is worth reiterating here that there is unlikely to be a precise oil level reported. Drivers will likely only be able to see a ‘normal or ‘not normal’ reading.
Capacitive
Capacitive sensors work by measuring the change in capacitance between two electrodes. When the oil level changes, the dielectric constant between the electrodes also changes, which is detected by the sensor. One capacitor is a sensor inside–maybe the middle–of the pan. The other capacitor is usually placed in the pan cover or on the block on the opposite side.
Capacitors have the ability to store energy in an electric field between these electrodes when a voltage or ‘potential’ is applied to the circuit. The property of capacitance relates the amount of energy stored in this field to the applied voltage or potential. By placing non-conductive material between the electrodes, the ability for the capacitor to store energy increases and so the capacitance increases. This material between the electrodes is referred to as the ‘dielectric’. As a dielectric liquid (like oil for example) is introduced between the electrodes of the capacitor, the capacitance changes proportionately and liquid level can be determined.
The key to capacitance systems is the software to interpret the capacitive data and translate it to what gets seen on the display by the user. Slosh and diagnostic algorithms have to be fairly precisely developed and tuned in order to be accurate. Slosh algorithms take out the noise within the data reported by sensors. extreme highs and lows are interrogated to ensure that moving fluids do not erroneously report low or high levels. Finally, the cleaned data is translated to an oil level and broadcasted over the CAN BUS to be reported by the infotainment domain to customers.
Ultrasonic
Ultrasonic sensors use ultrasonic waves to measure the distance between the sensor and the oil surface. The sensor emits an ultrasonic pulse, which travels through the air and reflects off the oil surface. The time it takes for the pulse to return is measured, and the oil level is calculated based on this time. A sensor is maybe placed at the bottom of the engine, pointed down towards the bottom of the pan–where all the oil collects.
The sensor emits a pulse travels through the air and reflects off the oil surface, and the time it takes for the pulse to return is measured. The oil level is calculated based on the interval, and the sensor sends a signal to the control system, indicating the oil level.
In terms of software and electrical, the ultrasound system has a similar control flow as the others. In this particular design, an ultrasonic sensor is commanded to take readings instead of passively collecting readings and broadcasting them back on the CAN BUS for consumption. The design could function either way, however. The key here is the logic for processing the signals must tackle the same problems: sloshing, foaming, and extreme low or high readings.
Conductive
Conductive oil level sensors use the conductivity of oil to measure the level of oil. A probe is inserted into the tank, and the electrical resistance between the probe and the tank is measured. The electrical resistance changes as the level of oil changes. This change in electrical resistance can be used to measure the level of oil. Conductive level sensors use a low-voltage and current-limited power source applied across separate electrodes. The power supply (in this case vehicle 12V) is matched to the conductivity of the liquid. Higher voltage versions are designed to operate in less conductive (higher-resistance) mediums–like oil.
The power source frequently incorporates some aspect of control, such as high-low or alternating pump control. A conductive liquid contacting both the longest probe (common) and a shorter probe (return) completes a conductive circuit.
The sequence diagram below shows that when the system is powered on and the Vehicle Control Module activates the power circuit. Because oil is naturally an insulator rather than a conductor, the power supply must step up the voltage while limiting current to safely push an electrical signal through the fluid. This energized circuit flows to the longest common probe situated in the oil pan. As the physical oil level rises or falls, the fluid acts as a bridge between this continuously energized common probe and a series of shorter return probes positioned at varying depths. When the oil touches a return probe, it completes a specific conductive circuit and transmits the returning current back to the Vehicle Control Module.
The Vehicle Control Module measures the electrical resistance across these completed circuits to correlate the active return probes to a specific fluid volume within the pan. Once the volume is calculated, the module handles two concurrent tasks. It sends a digital command to the dashboard display to update the visual interface and show the final oil level status to the driver. In systems equipped with active management, the module can simultaneously dispatch commands to a mechanical pump to automatically add or cycle fluid based on the detected level.
A notable gap in relying on conductive sensing for engine oil is that clean synthetic motor oil has extremely high electrical resistance. These systems often depend on the presence of microscopic wear metals, moisture, or specific chemical additives to achieve baseline conductivity. While conductive probes are highly reliable in aqueous fluids like engine coolant, using them in oil requires complex voltage step up circuits that can be sensitive to changes in oil formulation, temperature, or degradation over time. Because the dielectric properties or acoustic impedance of oil are more consistent than its conductivity, capacitive and ultrasonic methods are frequently chosen as mainstream alternatives for modern vehicle architectures.
Dipsticks Don’t Fail, But Sensors & Software Do
We aren’t luddites here. Technology, generally, is a boon to improving quality and the experience of owning a vehicle. Also, oil level sensors have been around for a decade or more. However, a dipstick has provided a redundancy to error prone software and sensors. These oil level sensors can fail at quite a few points:
Diagnosing an oil level sensor system requires evaluating variables far beyond the sensor hardware itself. The root cause analysis mapped out in the fishbone diagram breaks these failure modes into four interdependent categories: Fluid and Environmental, Hardware and Mechanical, Electrical and Wiring, and Software and Calibration.
The physical state of the engine oil fundamentally dictates the accuracy of any sensor technology. Thermal breakdown and extreme oxidation lead to heavy sludging, while mechanical shearing causes severe viscosity loss. When prolonged heat exposure degrades anti-foaming additives, the resulting aeration acts as an acoustic barrier that scatters ultrasonic signals. Furthermore, base fluid contamination from coolant intrusion, fuel dilution, or aftermarket chemical additives completely alters the dielectric and conductive baselines that the control module expects to see. Dynamic sloshing resulting from insufficient oil pan baffling also introduces erratic physical fluid levels that challenge the sensor’s measurement capabilities.
Beyond the fluid itself, the physical components operating inside the oil pan are exposed to continuous thermal and mechanical stress. Severe oil degradation produces a baked-on carbon varnish that can coat conductive sensor probes, acting as an electrical insulator, or cause the guide shafts on mechanical float sensors to bind entirely. Over extended mileage, plastic floats can saturate with oil and sink to the bottom of the pan. External hardware vulnerabilities include physical impact from road debris, vibration-induced mechanical fatigue, and housing leaks. In some designs, excessive internal baffling or manufacturing defects can actually isolate the sensor from the true fluid volume of the sump.
Even if the internal hardware functions perfectly, the electrical pathways bridging the sensor to the control module remain highly vulnerable. Because these sensors typically mount at the lowest point of the engine block or oil pan, the wiring harness is exposed to the elements. Connector corrosion and water intrusion are frequent issues. Harness chafing and thermal degradation near exhaust components create intermittent shorts to voltage or ground. These intermittent faults, often driven by micro-fretting at the connector terminals, introduce erratic resistance that translates into rapid, implausible data spikes on a diagnostic data stream.
Once those raw electrical signals reach the control module, the software must accurately interpret them into a usable volume measurement. Software failures frequently occur when the engine control unit relies on skewed dielectric or conductivity baselines caused by the degraded fluid mentioned earlier. In ultrasonic systems, acoustic scattering leads to lost echoes that the software must be programmed to handle gracefully. Broader algorithm failures include inadequate slosh filtering, incorrect volumetric calibration curves, or unhandled edge cases such as parking on steep inclines. If the software lacks robust rationality checks, it will fail to compensate for sensor drift and will pass mistranslated, erratic data directly to the driver display.
Serviceability will surely Suffer
One of the reasons cited by the Chief Engineer for this design change amounted to: Customers don’t check their oil and often do it incorrectly. Even if those things are true, technicians service these vehicles and have relied on the dipstick as a means to quickly assess whether oil is holding clues for failure.
Dipsticks enable technicians to rapidly check for conditions that would otherwise necessitate dropping the oil pan–driving up costs and reducing efficiency. First and foremost, dipsticks provide visual, physical confirmation of oil level. As mentioned previously, oil level sensors have quite a few failure points that can fool the sensor or cause it to fail. And, depending on the design pattern, could hide the true oil level until such a time that the level is critical. Once oil levels get critical enough, damage is already done. If the sensor is suspected to have failed, then the entire oil needs to be dumped to measure the actual level of the oil.
Technicians not only use the dipstick to check oil level, but they also use it to smell for certain conditions that traditional diagnostics haven’t been able to highlight. One key use case recently was a diesel engine with foul smelling oil. A leaking injector can cause fuel dilution and make oil smell pungent. This is an easy clue that will no longer be available to technicians. Certainly, other avenues exist to assess for leaking injectors; however, some of those methods take more time and are not as efficient–nor effective.
A capability to simply observe the condition of the oil is important. Oil can become cloudy when it is contaminated with coolant or water. Metal shavings (yes, I am looking at you GM 6.2L owners) can sometimes be seen on the dipstick when internal wear is present.
All of these very common conditions (and more) now can’t be monitored easily inside the service bay without dropping the pan or draining out all of the oil. Because these sensors are now a single point of failure they are also going to be another wear item that will need to be replaced routinely to ensure their accuracy. Customers are well known for delaying maintenance and ignoring signs until there is a complete failure. In this case, a faulty oil sensor may not display anything strange to a customer that is unawares. The result: a seized engine.
Oil level sensors are a great novelty that can make a vehicle feel more modern and have a certain amount of utility for basic oil life monitoring. But, that was when a redundant, simple system was available to provide a backstop in the event that a sensor might be in a failed state. Now, we are expected to believe that a much more complex system with numerous failure modes should be the single source of truth for a $100,000 SUV?