Subaru BRZ 2018 Owner's Manual page 275

(6)If your vehicle will be towing a trailer, load from your trailer will be
transferred to your vehicle. Consult this manual to determine how
this reduces the available cargo and luggage load capacity of your
vehicle.
( P. 492)
SUBARU does not recommend towing a trailer with your vehicle. Your
vehicle is not designed for trailer towing.
Example on your vehicle
When 2 people with the combined weight of 366 lb. (166 kg) are
riding in your vehicle, which has a total load capacity of 699 lb. (317
kg), the available amount of cargo and luggage load capacity will be
as follows:
699 lb. - 366 lb. = 333 lb. (317 kg -166 kg = 151 kg)
In this condition, if 2 more passengers with the combined weight of
258 lb. (117 kg) get on, the available cargo and luggage load will be
reduced as follows:
333 lb. - 258 lb. = 75 lb. (151 kg - 117 kg = 34 kg)
As shown in the example above, if the number of occupants
increases, the cargo and luggage load will be reduced by an amount
that equals the increased weight due to the additional occupants. In
other words, if an increase in the number of occupants causes an
excess of the total load capacity (combined weight of occupants plus
cargo and luggage load), you must reduce the cargo and luggage on
your vehicle.
2-5. Driving information
Cargo capacity
Total load capacity
2
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