Volvo 2006 C70 - Manual (Page 111)

Volvo recommends the use of synthetic engine oil when towing a trailer over long distances or in mountainous
areas.
WARNING!
Bumper-attached trailer hitches must not be used on Volvos, nor should safety chains be attached to the bumper.
Trailer hitches attaching to the vehicle's rear axle must not be used.
Never connect a trailer's hydraulic brake system directly to the vehicle brake system, nor a trailer's lighting system
directly to the vehicle lighting system. Consult a trained and qualified Volvo service technician for correct
installation.
When towing a trailer, the trailer's safety wire must be correctly fastened to the hole or hook provided in the trailer
hitch on the vehicle. The safety wire should never be fastened to or wound around the drawbar ball.
NOTE:
When parking the vehicle with a trailer on a hill, apply the parking brake before putting the gear selector in (P)ark,
or in reverse on models with a manual trans-
pg. 121 Starting and driving
Towing a trailer
mission. Always follow the trailer manufacturer's recommendations for wheel chocking.
When starting on a hill, put the gear selector in (D)rive before releasing the parking brake.
If you use the manual (Geartronic) shift positions while towing a trailer, or if the vehicle is equipped with a manual
transmission, make sure the gear you select does not put too much strain on the engine (using too high a gear).
The drawbar assembly/trailer hitch may be rated for trailers heavier than the vehicle is designed to tow. Please
adhere to Volvo's recommended trailer weights.
Avoid driving with a trailer on inclines exceeding 15%.
pg. 122 Starting and driving
Detachable trailer hitch
Installing the ball holder
If necessary, remove the cotter pin from the locking bolt and slide the locking bolt out of the hitch assembly.