My wife’s 2009 Matrix S 2.4L has about 55,000 miles on it. The recommended oil change interval is 5000 mi or 6 months.We used to do it seasonally - spring/fall. Because we now use it rarely, and mostly for local trips (under 15 mi 1-way - about 50% highway) we rarely get a 1000 miles on it in 6 months. The oil level is proper, and there is very little discoloration. Recently the garage recommended switching to semi-synthetic oil. We live in NH so winters can be quite cold.
The question is, how often should we change the oil? Should we do it by the miles, or months? Stick to 6-months interval (spring/fall) even if its only been 1000 miles since it was changed last?
Also, the recommended coolant change interval is 7 years/70,000 miles. It has not changed color nor has the level gone down. We are over the years, but lower than the miles. Should we get it done based on age or wait for 70K mi?