After I took my Ford Focus 2011 to the dealership for a free oil change I noticed a subtle, low hum coming from the car when I hit speeds past 40mph. At first it sounded like the engine of a louder car driving near me so it took me a couple days to realize that it was actually my car making the noise. I intended to bring the car right back to the dealership to complain about this but I kept getting preoccupied with my studies for my summer courses. It’s been roughly 3 weeks now and the low hum has gotten a lot louder now and can be heard over music.
The noise begins when I approach 40mph. The noise is probably at its loudest at speeds of 40mph-70mph. The noise is made even when I am not stepping on the accelerator or using the breaks. I haven’t tried putting the car in neutral at those speeds. Does anyone have an idea about what might be causing that noise? I want to have some idea about this before taking it back to the dealership this week, although I don’t really trust the dealership since my car seems to manifest a new problem after each visit. I’m hoping that it’s just something that isn’t major or expensive to repair.