It’s sort of clunky, mpg is terribly inaccurate, as is odometer tracking. Scan gauge definitely is the way to go.

This is one of the poorest implementations of an electronics product I've purchased on Amazon. The actual hardware is decent, so you figure someone could have spent an extra few days on the software... but no. Within 10 minutes of plugging it in, I found the following list of inexcusable issues:1) Changing the language to English leaves many screens showing (I think) Spanish.2) Many translations are misspelled3) Changing to units to Fahrenheit caused the Coolant Temperature Alarm to go off, and the alarm setting was only adjustable from 89 to 150some degrees, telling me that underneath the software still thought it was dealing with Celsius.4) Device cannot read most of the PID codes that it lists. I know that it's a device issue, because I have a proper (nGauge) device on my vehicle, which can read all the PIDs that this one cannot.The hardware actually comes across pretty decent... Nice packaging, screen size is decent, build quality is decent, but the software makes this ... landfill material.

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I’ve already shared several tales of my decrepit pickup in other Vine reviews, but it bears repeating here that the speedometer in my truck died. Repair is not a viable option. In response, I’ve acquired two different versions of GPS-driven speedometer displays as an alternative. In general, these products have served me well.But there are some drawbacks: When you start up, a GPS speedometer make take several minutes to acquire a satellite fix before displaying meaningful data. If you drive through a heavily-wooded area, through the concrete canyons of a large metropolis, or through a tunnel, satellite lock can be lost and the speedometer will cease to function.Another way to drive an aftermarket speedometer is to derive the vehicle’s speed from data on the OBD (on-board diagnostic) computer connector. The benefit here is that you aren’t relying on feeble radio signals to measure vehicle speed, rather, the engine computer provides that information itself, just as it does to the stock instrument cluster.The “Car HUD Display” from the “MR CARTOOL” store is an instrument that can perform this function. It plugs into the OBD2 connector (just about all cars/trucks in the last twenty years has one), the HUD Display reads your vehicle’s computer signals, and reports your speed on its screen. This instrument works perfectly in my late 90’s Chevy S-10. No need to wait for GPS satellites, no danger of speedometer malfunction in a tunnel, parking structure, or forest.The intended audience for this product is somewhat broader than my limited use-case. The instrument features inclinometers and selectable graphic displays showing the angular pitch and roll of your vehicle. Off-road enthusiasts would no doubt find great use for this information.The HUD also contains “rally” functions like a compass, clock, and timers. While it derives speed information from your vehicle’s OBD port, it contains a GPS receiver as well, providing navigational information like latitude and longitude.One of the unexpected features of the HUD is its ability to collect and display raw engine data. This includes RPM (you can set up the screen to function as a tachometer), temperatures, pressures, and other internal engine parameters. The display is crisp and fairly easy to read, despite its diminutive size.I do contest the notion that this product (or any of the dozens like it) can survive mounted to the top of a dashboard. Ordinary exposure to the sun has literally melted and warped the housing of instruments like this, which I’ve owned and used in the past. That doesn’t mean you shouldn’t buy this display—it simply means that you need to plan on mounting it someplace where it won’t be subject to high heat or direct exposure to intense sunlight.If I had but one complaint, it’s that instrument never shuts off. I had hoped that removing the ignition key would power down the display, but it doesn’t. I doubt the HUD draws much current, but it’s probably enough to flatten the battery over time, if you left the vehicle unused for days or weeks at time. An obvious improvement would be a change in firmware to power down the unit if vehicle speed remains at 0 MPH for an extended period of time... and then power it back up on an engine start. For now, I’m left plugging/unplugging the OBD cable.