11 Miles to the Gallon WHAT?

Hey everyone, well so far my little van is a dream machine, no problems at all.

However the gas gauge goes all over the place so it is not accurate.

However, 3 times now I emptied the tank driving, and filled it up, calculated the mileage and gallons and came up with 11 miles a gallon.

Now the engine is clean, doesn't burn any oil, 6 cylinder, nor prior type of "hot rod" work done.

No smoke, no smelly gas, no choking, and popping carburetor noises, and lastly, I do not drive over 53 miles an hour.

The mileage was back and forth about an average of say 45 lets say.

So,,,,,,WHAT GIVES ??//

Anyone have this same experience?

W.

A 12 bolt rear end gives worst mileage than a 10 bolt,,,,,,and does the odometer lie,,,,,,,,a speedometer is set up for a certain transmission, rear end and tires,,,,,,,,,find a mile marker or radar trailer,,,,,see if the odometer reads the correct distance,,,,,,,,,or speed

Need to determine the actual rear gear ratio!! Then consider wheel rim size-14,15?? Example- if you are running a rear ratio of say 3:70-4:11- mileage is going to suffer -due to rpm @ highway speeds being high (rpm). Our vans just were,nt designed to be aerodynamic at all!!

try this, get on highway with mile markers and get the
van up to 60 mph on speedo, at that speed you should
cover 1 mile every minute, and your odometer should be
covering a mile at every mile marker, this is the only way
I know to tell if your speedo it telling you the truth without
the use of a gps unit or having your speedo checked at a shop
that has the equipment to do that, very few shops have what it
takes to get this done, this is why I suggest the mile marker thing.
one other thing do you have a tachometer on your van?

What are people averaging for mpg? Please provide engine size

when I had the 230 3spd manual with 3.36 rear I would get about 16 hwy
with the 5.7/700r4 3.36 rear I get 19 hwy but it is throttle body injected no carbs!!!!!!!!

Im going to be running a 3 on the tree 170 straight six in my ford van , not sure of the gear ratio yet. Just wanted to have idea of what kind of gas millage I will be looking at. I was hoping for in the 18mpg range.

I get about 10-12 MPG with my '65 Hella Sunshine.  305HO v8, th350, 3.36 gears, 325/50r15 tires but I haul ass everywhere I go so its worth it.

The '64 wikivan gets closer to 15mpg.  Its got a 230 inline 6, a t10 4 speed, and 2.56 gears, 295/50r15 tires I also haul ass everywhere in this van too.

Both my vans run in the fast lane on the freeway at 70mph