My fiesta - details on left. Last serviced by Ford 2,500 miles ago, about 2 months ago. Today it comes up saying Oil change due service required on the display with orange spanner on the dash.

I know I can reset this (by holding a certain pedal down with the key in a certain position - can't recall exactly right now) but I want to know exactly what criteria causes this message.

Is it based purely on mileage since last reset?     does time period come into it?  , the car was serviced 363 days ago, so could it be influenced by that and not having been reset at the recent service (although that was 15,000 miles ago and service interval is 12,500 or one year whichever is first).

does it actually check the oil somehow? I ask this because it is diesel and the engine oil level looks high on dipstick which I know can be caused by incomplete DPF cleaning cycle and the diesel it uses to do this ends up in the sump with the oil, thinning it and raising the level.

So, does the car actually have any kind of sensors to take this into account (thinning oil and rising oil level) which raises the engine oil message on the dash?

Please let me know - I could just reset it and forget about it, but if it is trying to warn me about thinning oil caused by incomplete dpf cleaning cycles I ought to know.

(by the way, my usual journey to work is 33 miles each way, about 25 miles of the 33 mile journey is motorway/fast dual carriageway at about 70mph so I would have thought it has chances to do dpf properly)

 

service due indicators are solely based on time elapsed since last reset , usually 12 mths , no other parameters are monitored , such as milage or oil condition.

just reset it yourself if serviced only 2 mths ago......

 

At least Ford are finally fitting service indicators...there isn't one on the Mk2.5 Focus...probably why a lot of DV6s popped turbos on them.

Does your handbook not say how the service interval is worked out?  If it's on variable longlife servicing the PCM monitors various things (driving style, amount of fuel used, amount of times bonnet opened, amount of regens, etc) to determine when the oil should be changed.  I don't know if the Fiesta would be on longlife though, if it's just time & distance servicing then it'll just literally be done on mileage or days passed.

Unless it's changed recently, to reset Ford indicators is usually igniton on and press the brake and accelerator for about 30 seconds.

Diesel can fill the sump even on long distance engines, this was an issue on my mates 1.5TDCi Focus, as well as my 2008 1.6TDCi Focus.