It's the dilemma that any parent with a car has faced - do you spend hundreds of pounds on a car seat for your child that may only last a year or two?
Or do you buy a multi-group car seat that will last a decade or more and save yourself the financial pain of forking out for a replacement every few years?
It's a UK legal requirement for children to be secured in a child car seat when travelling from birth until they are 135cm tall or 12 years old, whichever comes first. So a multi-group car seat that spans a wide range of ages has undeniable appeal.
But given how much your child's body will change and grow, can manufacturers really ensure their car seats can be adjusted to fit your child and keep them safe throughout this period?
Read on to find out, plus discover the models we've tested that cover a range of ages.
A multi-group seat is a car seat that spans a wide range of ages. You might see multi-group seats also referred to as a 'combination seat'.
If it's a car seat that's approved to older regulations (R44), then it will be a group 1/2/3 (9kg to 36kg, or nine months to 12 years) or group 0+/1/2/3 seat (newborn to 36kg or birth to around 12 years old).
For i-Size seats that are approved to the newer R129 regulations, they span heights instead of weights. We tend to see mainly 40cm to 105cm, which equates to birth to around four years old. But we're now starting to see a few more i-Size seats that last for longer - up to 125cm - which is about six years old.
The obvious pro is the cost as you can save a lot of money by not buying multiple car seats.
While most multi-group models approved to the older R44 regulations are forward-facing only, there are now increasing numbers of extended rearward-facing multi-group car seats approved to the newer R129 regulations. These allow you to keep your child rearward-facing until four years old.
That's important because if you end up in a front-on collision, our tests show that rear-facing car seats will offer a higher level of protection to a child's delicate head, neck and spine, compared with a forward-facing toddler seat.
The negatives is that it can be harder to find a multi-group car seat you can trust. A number of multi-group seats don't score highly in our tests for a range of reasons which include:
Here are five car seats we've tested that span a range of heights and weights. Click through to the full reviews to find out if they're worth buying or not.
The recently tested Cybex Pallas G i-Size is a forward-facing car seat that's approved for use for children from 76cm to 150cm tall, which is about 18 months to 12 years old. It's installed using Isofix and also has a top tether, but can be belted into place once your child reaches a height of 100cm.
The main feature of this car seat is the adjustable impact shield that takes the place of a traditional harness. This should be used for children who weigh less than 21kg and are up to 105cm tall. Once your child reaches 100cm, you can switch to the regular vehicle seat belt.
Not every child will be a fan of the impact shield, but to improve the fit and comfort of the seat, the Pallas G i-Size features both a reclining seat and a three-position reclining headrest.
The Axkid One+ is an i-Size extended rearward-facing car seat that's approved for children between 40cm and 125cm tall, which is from birth to around six years old.
This car seat uses an integrated Isofix base with a support leg, so it may not be suitable for cars that have underfloor storage within the rear footwell.
A dial at the front of the seat will adjust the headrest into one of 12 positions and a sliding mechanism allows you to move the car seat by up to a 30cm to meet the ever increasing demand for legroom as your child grows.
Ventilation holes should also help keep your child cool during hot weather.
The forward-facing Britax Ru00f6mer Advansafix M i-Size can't be used from birth, as it's approved for use with children measuring 76cm to 150cm tall. That's roughly from 18 months to 12 years old, so still a long lifespan for a car seat.
This car seat features a five-point harness that needs to be used when the child weighs less than 21kg. Installation is via Isofix point and a V-shaped top-tether strap.
You can switch over to the car's three-point seatbelt once the child weighs 21kg, but you can still click the seat into the Isofix for added stability.
You don't need to remove any parts when switching between the five-point harness and seatbelt, and the seat will recline.
Music to any parent's ears: the seat cover is also machine washable.
Suitable for children from about one to 12 years old, the Recaro Tian Elite is a forward-facing Group 1/2/3 car seat that's approved for use with children from 9kg to 36kg.
The integrated three-point harness will secure children up to 18kg (four years old or so), but the car's normal seat belt can be used from 15kg.
Once the child is in Group 2/3, the seat's integrated Isofix can be used in addition to the vehicle seatbelt.
The seat base is extendable to provide more support for under your child's legs and the covers are machine washable.
An extra feature on the Tian Elite is the integrated speakers in the headrest. Attach a phone or MP3 player using the 3.5mm headphone input and your child will be able to listen to music as you travel.
The Nuna Myti is an i-Size-approved car seat designed to last from 15 months up to 12 years old. It was first launched in January 2019 and we tested it in October of that year. It's not part of our most recently tested batch, but worth mentioning as it's a 10 years old-plus car seat.
The seat uses the five-point harness until your child measures 105cm, at which point you switch to using the adult seatbelt. You fit it via Isofix anchor points and the connections have handy coloured indicators to help make installation that little bit easier.
This seat has what the manufacturer calls a '2D growth system'. This essentially means that you can pull up the headrest and back rest, and expand the shoulder space as your child grows. There are nine positions.
It also has a three-position recline, which may provide a more comfortable sleeping position for your child.
When it comes to safety and child car seat testing, Which? is ahead of the curve.
Derived from Euro NCAP assessments, our experts have specially designed the crash tests to be more demanding than the legal minimum standard requires.
A good car seat should be able to protect your child well enough in both front and side-on crashes, as you can't tell what type of accident you may be involved in.
During the course of our tests, we use different-sized crash dummies to cater for all the different modes a car seat can be used in. We can go through as many as 15 samples of the same seat to get the final crash-test result and then limit the score to the worst-case scenario.