this is the most common type, and models come in a wide range of sizes and prices. Generally, the larger the dial, the easier it is to read – but you also want to consider storing the gauge in your car.
Digital gauges: these are generally the easiest to read, especially if their display is backlit. However, you'll have to replace their battery every now and then, so there'll be a small ongoing cost.
Pencil gauges: we didn't find this type as easy to read as others, but pencil models are generally cheap and very easy to store.