Hi my car is having moments where I will be driving and the car will start to use more fuel and the engine tone also changes can anyoba give me a clue of what it might be please

 

More info please.

What year? What engine? Automatic or manual transmission? Are you using cruise control? How do you know its using more fuel?

 

It is Mazda 3 Skyactiv Sport 2015 2.2d. Manual. MPG on my computer shows the drop. As well as a change in engine tone seems to grumble but no warning lights or change in performance.Not in cruise control

 

More than likely you are watching the real time fuel economy, which is an instantaneous reading, rather than a long term average. Any increase or decrease in throttle by your right foot will change engine revs & noise.

How long have you owned it/ driven it?

If in doubt, take it to Mazda.

 

Hi 8 weeks even the average starts plummeting it has done it in cruise control. At 55mph it was doing 34 mpg

 

It needs to go to Mazda for further diagnostics. They are the experts.

 

Is it a Diesel? 2.2d means diesel right? Does it have a DPF? I believe it does if its diesel. I would bet you are seeing the additional fuel usage during an automatic regen cycle to clear the DPF of particulate. Look in your owners manual and it explains what that is. During the regen the gas mileage will drop very very low to allow for particulate burn-off. During this time it is purposely pumping extra fuel into the exhaust to cause the burn. Therefore your mileage shows really low. In the US this is called Tier 4 emissions and its on all diesel engines for consumer use.

Based on other cars I would expect the mileage to drop for a period of 10-15 miles of continuous driving into the range of 15 MPG.

The owners manual can explain how often it might happen.

RGAZ

 

Hi just had it checked out and was told this is what it is. Thanks.

 

Are you going to keep us in suspense?

 

Sorry. But yes when the car goes into regeneration mode it will use more fuel until it completes its cycle.