A 2.7 L is hardly a small 4 cylinder engine. It is about as big as is in the market. Your 2003 4runner was rated at 15-19or 17 overall. Makes me wonder just how you were calculating your fuel mileage.
I don’t know if your 2.7 L engine has balance shafts, I am not a fan of balance shaft engines because it takes extra fuel to spin those shafts. They make the engine run smoother but those shafts take power and fuel to operate.
You have a heavy truck with a 4 cylinder in it thats the only thing wrong with it … The law of physics.
17 overall is garbage for a 4 cylinder! I achieved 17 overall in a 2013 crew cab 5.0 v8 4wd f150. Where does the 17 mpg come from? Epa combined rating?
Yes, EPA rating for the 2003 4Runner V6 was 15 city , 19 highway and 17 overall.