If you clean 100 lbs of junk out of your car, how much will your fuel-inefficiency increase?

Some but not much. You see more a difference if you do lot of street (stop and go) driving vs. hwy driving.





There are few thing you can do to save (or maximize) gas MPG. First get a tune-up.





(1) spark plugs


(2) spark plug wires


(3) distributors, coil, rotors (if you have them).


(4) new air filter


(5) PCV


(6) correct tire pressure


(7) clear the trunk of useless heavy items


(8) spray clean MAF sensor.








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Forget all those "SAVE GAS" scams. This was on NBC morning TV show. The difference is as much as 38% (their claim). There are very simple rules to save gas:





(1) drive slow - not too much past 55


(2) accelerate slowly


(3) don't brake unnecessarily


(4) use cruise control - whenever it is safe to do so.





Don't coast - it is NOT safe and it does NOT save gas.





The above really works. Using those simple rules I was able to drive from Boston to NYC (210.5 miles) on just 5.112 gallon (94 Civic). That's 41 MPG (94 Civic 187K miles). Actually I was speeding at 72 MPH so I could do even better at 55.





WOW !!








Good Luck...
If you clean 100 lbs of junk out of your car, how much will your fuel-inefficiency increase?
3,408 lbs for a avg. car that is about 3% of the weight of the car.





At the most you could hope for is 3% but you would never get that much because efficency doesn't work in a linear scale





I would guess less than 1mpg. It would still add up over a year.