Sorry I'm not being clear. I don't actually care if the tank is 16 or 15 or 14 or 5000 gallons, the capacity of the tank has ZERO impact on mpg. The 14 gallon tank figure comes from the idea that the OP is doing fill-ups at an interval that precludes having to worry about running out of gas. And craig thank you for pointing out that you cannot fully empty the tank I think people are forgetting that the entire tank size is not useable. I would also posit that you cannot really fully fill the tank, as there is typically area in the top of most tanks that cannot be filled. So even though the tank is listed to be able to hold 16 gallons, you would be very hard pressed to get 16 gallons into it, and even harder to use all 16 gallons out of it. And with that I'm done here. because this argument is stupid. This is like all the people that get butt hurt when they buy a new computer/cell phone/tablet and then complain there is less storage space than advertised because there is software installed to make the device function.
I would think, if you were hauling 5000 gallons of gas around, your mileage would be worse, that's a lot of weight.
I believe the change came in '75 or '76. I own a '71, two 72's, 4 73's, a '74, two 76's and a '77 Maverick.. Every original '71-'74 Maverick I've seen or had have the 14 gallon tank. The later, larger tanks will bolt in (albeit with interference with the rear valance on small bumper cars), but I've never seen a early car with one stock. The tank in my daily driver came from a '73 4 door originally, and I usually go another 10 or so miles after the gauge hits E before refilling. Usually takes right around 13 - 13.5 gallons to fill it back up. I have ran the car out of gas a number of times (opps), and it took right under 14 to fill it back up. I've crammed a little over 14 in it before, but it was all the way up in the top of the filler neck and actually overflowed a bit.. The only reason tank size came into question here is because the original poster did not provide enough information to come up with a ball park economy number. So we have to assume, since he has a '72, that he has the 14 gallon tank, and therefore is going the distance he stated on 14 gallons or less, unless he states otherwise. Have only ever seen slight gains on my car with 93 octane, and had to advance the timing across the board to make any difference, otherwise it actually hurt my economy. It wasn't anywhere near enough gain to make the additional cost of fuel worth it. High octane gas in low compression motor just isn't optimal. I do see up to 4-5 mpg differences with 87 octane depending on where I buy it. I consistently get the best economy with gas from RaceTrac or Quick Trip. Shell is decent as well. BP is middle of the road most of the time. The worst I get is from Kroger fuel stations or these new Valero stations that are popping up around here. On my car I've always been determining the economy from the first time I put gas in the car with a completely empty tank, dividing the mileage driven by the number of gallons I put in it at last fill up. Of course, there is a certain error rate since you generally don't run your car completely out of gas, but if you did factor in that unused gas, it would only show an overall improvement economy, not hurt it.
It’s a mathematical equation…nothing to figure out except how to subtract 1 number from another number to get a total and then divide a number into another number.
