I have exactly the same cleaner. It is OK but its not perfect for car parts necessarily.
Most car parts are either oily/greasy, or have surface corrosion. The oily/greasy parts tend to emulsify with water and this creates a barrier that prevents the waves impacting the surface. The end result tends to be slightly slimy parts that you need to clean by hand and put back in.
Be careful with detergent and aluminium parts. I have had a few where the surface was marked by the ultrasonic bubbles, or where strong detergents have discoloured/etched the metal. I find a squirt of normal washing up liquid is sufficient (you will need to mix it in), nothing stronger. Since the water is not circulated, the detergent doesn't really do much more than putting it in a hot bath. It's not really a parts washer. For its size, I find the ultrasonic power is not high enough.
Heating will also take an age as the heating element is only a few hundred watts - 2 or 3 kettles worth of boiling water is a good way to get started otherwise you will be waiting for a few hours. Using the ultrasonic at the same time as the heater will help heat it quicker and degas the solution.
You can fit a B16 engine block into one of these (sticking up, not laying flat). It probably helped shift some dirt, but I wouldn't say it came out beautiful like a proper hot dip at a machine shop. A few 15minute sessions in this + a strong jet wash after is probably a bit better than just the jetwash on it's own. It really struggles with grease/oils. What does get removed ends up floating at the surface, so when you pull the item out it just ends up covered in gunk again sometimes.
I suspect plastic parts or smaller/lighter items will work perfectly fine. But stick a hub, throttle body, vtec solenoid in here and it just doesn't really come out that brill.
I have the tiny 1litre one also, which is much more useful for electronics and jewellery. I last used the large one to clean a massive graphics card PCB, there is no power setting, only time - it might be too vigour for delicate items/surfaces.
Some practical tips:
1) When its full of water, its bloody heavy. Make sure you have the device on a bench, with the drain pointing somewhere you can place a bucket. Do not put it on the floor
2) Start it off with hot water from a kettle otherwise you will wait a long time. The temperature gauge has a lag also.
3) My lid handle was only spot welded on with a tiny battery spot welder and came off. Put a new handle on it to aid removal. The recess is small, and you will soon burn your knuckles or end up dripping scalding water all down your self as it runs off the lid.