Bad fuel mileage issue (2000 Protege)

[NScrilla]

Hey guys,

My 2000 1.6L standard protege used to get good mileage. I remember it was about 11.6 KM/L and 12 KM/L which is almost 30 MPG. That's what it is supposed to get. Now i seem to only be getting 8.75 KM/L which is around 20 MPG.... Now it is supposed to get 31 on highway and 25 in the city. Most of my driving is in the city now where it used to be highway but it still seems low to me.

The tires have tread on them. The alignment was done recently. It does not smoke and i think the engine is making good compression. No check engine light is on. Sometimes the brake light comes on but not often and i think it is just a faulty sensor or something. It runs good and there are no noticeable issues with the engine when driving.

Any ideas on why i'm not getting the mileage i should be getting? Car has 190,000 KM on it so far. I do drive it kind of hard but nothing too bad.

Thanks!

 

[tireboy]

Air filter clean?? Spark plugs?? When did you service it last??

 

[allenlee888]

Your car's fuel consumption has decreased from 11.6-12 kilometers per liter (about 7.8 liters per 100 kilometers) to 8.75 kilometers per liter (about 8.8 liters per 100 kilometers), which is indeed high, especially for an old car with an age of 300000 kilometers. This is likely the result of multiple factors working together.
Firstly, engine carbon buildup is the top suspect. Long term low-speed driving in urban areas, coupled with your self perceived "driving a bit aggressively", can easily lead to carbon buildup in the intake valve and combustion chamber, affecting fuel combustion efficiency and naturally increasing fuel consumption. Secondly, check the tire pressure. Although you have just done four-wheel alignment, insufficient tire pressure can significantly increase rolling resistance and lead to increased fuel consumption. Thirdly, the braking system. You mentioned that the brake lights occasionally come on, and if the brake cylinder does not return properly, it can cause slight dragging and increase driving resistance. Finally, aging components such as oxygen sensors and spark plugs can also affect air-fuel ratio and ignition efficiency, leading to increased fuel consumption.
I suggest you prioritize checking the engine carbon deposits and brake system, while ensuring that the tire pressure is normal. If the problem persists, consider troubleshooting electronic components such as oxygen sensors. Rising fuel consumption in old cars is a common phenomenon, but it can usually be improved through targeted maintenance.

https://www.echemi.com/

 

[walt]

A dirty MAF sensor can cause sudden drop in mileage. They are fragile so use care when cleaning. As usual they make a special cleaner for everything but I use brake cleaner.