I've noticed a reduction in the MPG of Hyundai i20 2014 model Mark 1.5, 1.25L, there are no warning lights on the dashboard, the car is just been serviced and moted and I changed the spark plugs air filter and pollen filter, however im at a loss at the reduction in mpg, drives exactly as normal no misfiring, starts stops perfectly, engine temperature gauge is spot on, heating comes on nice and warm quickly. I should add this mpg reduction was also before the service.

It's difficult to gauge the exact reduction but I'd say 4 or 5 miles per gallon in the in town and also suburban driving. I filled some petrol last week and on the MPG reading was going down and down and down as low as 10 miles to the gallon (I've never seen it that low) which spooked me, it has increased to high 20s since but still not great

The only thing I've noticed is the bottom coolant hose is cold even after a long run, whereas the top hose is warm, is this normal? From what I can research the thermostat is coming from the bottom hose into the engine, so I'm thinking maybe by the thermostat is open or is not fully closed therfore warm coolant is not staying in the bottom hose and the colder coolant coming from the radiator is entering the engine and reducing mpg

Edited by -Kat- on 25/12/2021 at 22:27