Put the ignition on but don't start the car, flick through the display until the 'miles to next service' one is showing. Press and hold the button on the end of the stalk and the display will flash eight times, release the button and wait and the new service interval should appear.
Bad lub and you are burning money away without even realising it. Fuel consumption can creep up by over 10%......or 10 miles in a 100 and so that's £1-35 to 50p-ish......the £20 of lubricant suddenly looks a good buy.
You should only go by the car manufacturers recommended oil change intervals if you use the recommended oil. If you are using a budget oil then change it more frequently and change the oil filter too.