Engine RPMĪnother indicator of how efficiently your engine is operating is its revolutions per minute (RPM). Even though the engine is using too little fuel, this will be made up by issues in other areas, which will result in a less efficient engine and therefore a more costly one to run. Having said that it’s also a problem if the values are too low. The problem could be caused by the fuel injection system overcompensating for a vacuum leak for example. If the fuel trims are both too high, then your car is using too much fuel, which means it’s not at its best efficiency.
However, you’d expect a healthy engine with a properly functioning fuel injection system to have an STFT reading between -10.0% and 10.0%, and an LTFT reading between -5.0% and 5.0%.
Of course nothing is perfect, so you probably won’t be seeing readings of 0.0% for both STFT and LTFT. They both represent the same thing, LTFT is just calculated over a longer period of time, so is more of an average value. An OBD2 scanner will give two values for fuel trims, a long term fuel trim (LTFT) and a short term fuel trim (STFT). If the reading is negative, below 0.0%, then there is too little fuel being released. If the reading is a positive number, so above 0.0%, then this means that too much fuel is being released. Fuel trims are represented on the OBD2 screen by a percentage, where a percentage of 0.0% suggests that the fuel system is working perfectly, with the right amount of fuel being released into the engine. Fuel trims basically refer to how much fuel is being released into the engine by the fuel delivery system. So, how can you use an OBD2 scanner to investigate fuel economy? Well, part of the live data stream from an OBD2 diagnostic scan tool that is displayed is a reading called Fuel Trim. If an engine is overusing fuel, then this could suggest a few different problems with the fuel system, which we’ll talk about later.
If an engine is using too much fuel, then the engine will have a very low economy and be more expensive to run. You want to make sure that your engine is using fuel at the correct rate for your vehicle. If you already have an OBD2 scan tool and want to investigate your car’s efficiency, then there’s a few key things that you’ll want to look into. Head there to find out about the best OBD2 scan tools that have live data functions included, which you can use the check the efficiency of your car’s engine components. You can find lots of information about various OBD tools at, who regularly review different OBD2 scanners. This of course saves a lot of time and money. Using OBD2 scanners to delve into the live data of your car is a much cheaper alternative than sending the vehicle off for testing, and you can get a good idea of how the engine is performing just by using the scanner. We can use the live data function to look into fuel economy, thermal efficiency and general engine performance. A diagnostic scanner with a live data function is the best thing to use to check the efficiency of your motor.
Most OBD2 diagnostic scanners also include a feature called live data, or data stream, which is what you’re looking for if you need to do some efficiency checks. An OBD2 scanner is a diagnostic tool that is used to read and clear codes, run system checks, and sometimes make adjustments to a car’s CPU. One of the easiest ways to check the efficiency of your car’s engine and its components is to use an OBD2 scanner.