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They are a variety of fuse sizes in use in automotive applications:

(image from Wikipedia by user Havarhen, CC-BY-SA-3.0 license)

My 1989 Opel Vectra used regular fuse size, but if I remember correctly my 2011 Toyota Yaris used low-profile mini fuses. I haven't yet taken a look at what fuses my 2016 Toyota RAV4 hybrid uses, but wouldn't be surprised to find if they also are low-profile mini fuses.

What is the reason for newer cars using smaller fuses in general? For example, Wikipedia says that those mini fuses were developed in 1990s. I don't think a fuse box with either fuse size uses too much space. Also, the material cost differences are minimal compared to the weight of the car. Serviceability seems to reduce little: the smaller the fuse is, the harder it is to change it and the easier it is to lose it if accidentally dropped, although I don't find those mini fuses overly difficult to change.

So, there must be some reason to use those small fuses. What is it?

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Fuses keep changing, glass fuses used to be the standard and, on cars, there were only a few ratings 5A, 10A and usually 2 or 3 circuits that were fused.

Now circuits tend to be controlled by various computers : engine control unit, body control unit, gearbox ... the list goes on. But the circuits for these only require low currents 1, 2 or more amps so the fuses are now smaller but there are many more circuits that are protected.

Cars now have 2 or more fuse boxes - one under the bonnet and another under the dash. Given that if the older larger fuses were still in use for all circuits then the boxes would be much larger.

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    Good answer. I also believe this is a result of design having to be able to fit more fuses in tighter spaces. – CharlieRB Jul 17 '17 at 15:31
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    saving weight is one of the reasons for going to the micro3 fuse in the future. – Ben Jul 17 '17 at 16:53

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