Fuel efficiency trouble with 2011 CX7
 

My car is a 2011 CX7. I used to get decent gas mileage until I came back after a road trip last month. I did a proper car service before the trip. I got no issues relating to fuel efficiency or anything else during the trip as well. A couple of weeks after the trip I noticed that fuel efficiency has come down significantly. I though it was some leak or something, but couldn't find any evidence of leak in the garage. I am someone who tries to get maximum fuel efficiency and follows advises for the same from experts. This sudden dip in the fuel efficiency bugs me and want to correct it asap. I would like some help or advice here. Thanks!

What kind of drop have you seen? Have you noticed any other quirks in relation to the drop e.g. loss of power, a noise from the engine? Have you changed tyres or checked the pressures lately?

Hi
Low tyre pressure could be a simple cause - to my shame, I hadn't spotted one corner of our Honda drop to 13 psi rather than 33, explains the poorer than average last tank full...

A tired 02 sensor will cause a significant drop in MPG. Of course all the normal maintenance things should be addressed first.

In addition, did change happen after a recent fill up? Has the weather and temperatures been the same?

Definitely check the tire pressures. Modern tires may not actually look low until they are really low.

I didn't notice any noticeable issues with power or noise from engine. May be I should look for something. Also, I have checked tire pressure recently and refilled it. But I think 2 rear tires are close to the end of their lives. Do you think it can be the reason? I believe there was no big change in temperature or climate to cause such a change.

Worn tyres wont give worse economy necessarily. If its just had a service, check the HT leads on the spark plugs are all on properly, and check the airbox and all related pipes are connected properly too.

Worn tires generally improve fuel economy.

Just a thought, could you have had the pump cut off very early on the previous full tank?
I'm pretty sure i've had some false high then false low mpg figures with a dodgy pump cutting out a few litres too soon.

Regardless of where the pump stops, the fuel quantity pumped into the tank is displayed beside the price and that is how you calculate l/100 Km

But if tajy drove to the U.S on his trip that may be his problem. Every car I have owned operated poorly when visiting the U.S.A