Change the gear oil and blake/clutch fluid if that hasn't been done. I would imagine that the coolant was replaced the timing belt was done.
Chevy Sonics are known to have coolant leaks in multiple places:
The water pump was defective and GM updated it. Hopefully the water pump was replaced when the timing belt was done.
The Thermostat housing is plastic and is prone to cracking over time. There are metal replacement ones. It can be DIY and the part is cheap.
if overlow tank is dark and discolored replace it. It is cheap and simple to DIY. The nipple at where the coolant line attaches to it gets brittle and breaks causing a leak.
The oil cooler is also a problem area. The o-rings degrade over time and leak. Mine failed at 88K
The radiator housing is plastic and in rare cases can crack. Even that can be DIYed for $200.00, a few beers, and a day of tinkering. (mine wasn't leaking, but I went OCD and replaced all of the hoses and radiator as PM-my cooling system will be leak free for many years now.)
Replace spark plugs and check to see if the old ones are are soaked in oil. The valve cover gasket seals degrade over time and alow oil to pass into the spark plug holes. If that is the case then also replace the valve cover and coil pack. The valve cover also contains the PCV valve. Everything listed in this paragraph is can be DIY. The parts including plug socket, Harbor Freight e-torx socket set, and RTV run @$200.00
I do not mean to scare you. Every car made has problem areas. The Sonic kryptonite is the cooling system. Repairs are not catistrophic because parts are cheap and the car is generally easy to work on. If you can DIY some of the easy repairs, it will be very cheap to maintain. Mine has the lowest cost of ownership of any car that I have owned. I have owen many over my lifetime
I have a 2014 LT 1.8 5 speed hatcback that has 122K. It doesn't burn a drop of oil and everything works as it should. It has the original clutch and shows no sign of slippage and the gear still engage smoothly.
Check the cooling system for leaks and change the oil regularly and it will last for many more miles.
WINTER/SNOW
I live in Pittsburgh It and was horrible to drive in the winter with the stock 15" rims and Hankook tires that came with it. I put on 17" rims from a Chevy Cruise Eco model and mounted All- Season Sport tires on them. (Goodyear Eagle Sport) . The Eco model rims are forged, allowing them to be light. They weigh the same as the 15's. That means that the unsprung mass is the same, but the contact patch is much larger. The rim swap made my car a blast to drive on twisty roads. For the wInter I swap out the rims with the 15"s that have good dedicated snow tires on them and the car will go just about anywhere in snow. The rims are @50-75 each at a junkyard
Since I live in the salt belt, I fluid film the car every year. It has zero rust.
