When it comes to most diesel vehicles, the recommended service period is every 5,000 km or 6 months, whichever comes first. However, this service interval can differ quite significantly depending on the make and model of your car, as well as how much you drive on a regular basis. More of a city driver? Driving short distances on a regular basis can cause the oil in diesel cars to accumulate gunk or other contaminants. This means you may need more frequent oil changes than your highway and long journey driving counterparts. It can be tricky to determine when to bring your car in for servicing. So to make that thought process a little simpler; here are 5 key signs that your diesel car needs to be serviced.