The windshield on my Accord cracked recently, and yes, I have an appointment to have it replaced. Since the windshield cracked, my gas mileage is significantly better. And I do mean significantly. So much so that when I first noticed it, I actually thought my gas gauge had malfunctioned. My question is this - has anybody else ever heard of this? I assume that somehow the crack has affected the aerodynamics of the car? Not being at all mechanically inclined, I am not sure how else to account for the change. I drive the same route every day, the same commute, approximately the same speed, purchase my gas predominantly at the same two stations, same type of fuel, have all maintenance done as required by the dealership, same tires. Nothing else has changed except the crack in the windshield. The windshield will be replaced so I assume my mileage will decline again, unfortunately.
Oh how I wish you were right! You would be a billionaire.
Zero chance that there is any relationship between a windshield crack and mileage.
The pump probably switched off early and did not fully fill the tank. Or you forgot to carry the 4 when doing your mileage calculation. Or you are relying on a faulty gauge. Sorry.
Maybe you have been subconsciously lifting you foot a little, thinking that the windshield could break all the way and come in on you. Not much chance of that happening either, unless it’s really CRACKED badly, through all three layers.
Since you’re getting it replaced anyway, do this in the name of automotive science:
-Take a brick or large stone.
-Use it to bust your windshield out completely.
-Put some WW1 airman googles on. Optionally, wrap a shawl around your mouth. You need these things for protection against bugs and road debris while driving. Sure, it will look silly but this is science, after all.
-Start driving and carefully see whether your gas mileage is affected.
-Report back so we can draw a conclusion.
You could be a wild driver, and now that you have a cracked windshield you’ve slowed down and drive more gently. This is a remote possibility. I agree with others that the condition of your windshield has ZERO effect on your gas mileage, unless there is NO windshield.
I measure mpg over 3 to 4 fill-ups (1000 to 1200 miles) by dividing the total distance by gallons of gas. I’ve found mpg measurements based on single fill-up are not accurate.