Cx5 2.2d fuel economy dropped suddenly? Would oil change cause this?
 

Hi.
I've owned my cx5 now for a couple of years but during the past winter the fuel economy suddenly dropped. Normally get around 44mpg but now 36mpg.
I did change the oil myself over the winter and used castrol magnetec. According to the manual besides Mazda own brand any C3 grade engine oil should be ok. Could this be the cause of the drop in mpg or just a coincidence and more likely something else not right?
Cheers Dave

Did you reset the Oil data?

When did it last go into Mazda for a PCM software update?

Any fault codes?

Thanks for the quick reply.
I have an obd2 Bluetooth (Only a cheap eBay one) but that isn't showing any fault codes.
By reset oil data do you mean just the miles left counter for next change?
As for mazda it hasn't been there for a while as I planned to do the servicing myself.
Is due to go in for the recalls on the boot struts soon though.

You must reset the oil data every service.

I would take it to Mazda for a Oil Data reset, PCM update & a code check ( Mazda's tester reads more codes than aftermarket testers)

What does the oil data reset do?
Is it something you can't do yourself?
not just reset the miles back on the dashboard after changing the oil?

So spoke with a tech at local mazda dealer today.
He suggests the problem is most likely the car needing an injector relearn and not anything to do with the oil change or reset.
They advise me to bring it in for a fault code check at £64.20 and if nothing comes up have an injector relearn at £25.
As for oil data reset he said that shouldn't make any difference as it on give a display as to when to change oil. But if you want that reset after changing the oil yourself it will cost £25. Starts to eat away at the savings of doing your own servicing :/.
He says you don't have to use skyactiv oil as long as it's a low saps grade C3 oil it should be fine.
What do you think of his advice? Is the next step to do as he says and have a fault code check and injector relearn?
cheers

Forgot to add. I used castrol magnetec. Same spec etc.
Any recommended oils out there to use besides Mazda expensive own brand?

Any recommended oils out there to use besides Mazda expensive own brand?

The oil data is not the service reminder. Its a system inside the ECU that calculates the condition of the oil as it degrades between services.

Its critical that it is reset every service, otherwise the ECU doesn't know the oil is fresh.

Oil data reset, injector relearn, code check & ECU software update SHOULD all included in the dealership service ( it is at my Dealership)

There would be no reason to ever think an oil change is affecting your mpg.