I own a 2010 KIA Ceed with a 90 HP 1.4 liter engine and 5 speed manual. I noticed that the last 700 kilometers about 420 miles the fuel consumption went up 11%. The vehicle has 159K km. or almost 100K miles. I switched from 5W30 to 10W40 the last oil change but that was 8,500 kilometers or 5K miles ago. I will change the oil soon. I switched grades to reduce oil consumption. Thank You very much for any advice.
Well, it's probably a combination of two things, heavier oil will get worse gas mileage and obviously since it's burning oil the engine is wearing out. And as an engine wears out. Of course it gets worse gas mileage. You need to check things like spark plugs, air filter, fuel filter, and all that stuff if they're old and dirty but as they age and if you put in heavier oil it will start to get worse gas mileage
@scottykilmer Thank You very much for your insight and advice. I must confess that I use this site to get answers but rarely give advice because I have only a small amount of automotive knowledge.