There can be so many factors for low fuel average. I'm not owner of this car, i have JDM WagonR. Here are some tips :
First of all , try to get the original owner's manual of the car model , in there you will find the engine oil grade and many other helpful things like tyre pressure to keep, etc.
- Get best quality fully synthetic engine oil ( my recommendation is LiquiMoli 5w30 , or Zic 0w20 A+ or KIXX same , dont go for these shell/caltex etc)
- Also try to get OEM genuine or atleast Imported (malaysian etc) oil filter . There are original mitsubishi Sale and Service centers contact them.
Also if needed, get your throttle body cleaned from a good workshop who know how to work with JDMs.
now the driving tips:
- Use HOBC/Hi-Octane petrol with Super Regular 60-40 ratio
- Drive with light foot, gradually accelerate, try to keep the speedo meter mostly "green" .
- Tyre inflation , very important, keep it around 35-36 psi. Don't listen to the outdated 30psi recommendation of these local mechanics etc.
- depending on your driving route conditions, every 2 weeks get your air filter and radiator cleaned using air pressure.
Try all these in sha Allah you will get good fuel economy.