Jump to content

Gas mileage down

Recommended Posts

I spent the last week (about 30-40 minutes every morning before it got hot:o) trying to figure out why my blue/white 55 is getting lousy mileage.  It is getting 12-13 mpg and the expected mileage should be 14-16 for the same trips.  It runs flawlessly.

Ignition:  plugs and wires good; timing good; vacuum and mechanical advance working; dwell good.

Carburetor:  dry outside and inside even with the electric pump running; rods working as expected; fuel pressure with and without electric pump good; electric pump has become necessary most of the time due to vapor lock and boils the gas out of the bowls when parked.

It is probably the gas.  I found an article dated May1, where the EPA will allow (due to Covid) winter blend gas (max ethanol and butane added) for a month and extensions as needed.  Winter blend boils at 100* F, so my gas is boiling and evaporating while it is parked!  It will get cooler someday and gasoline blends will be appropriate for the season again.

Link to post
Share on other sites

Manifold vacuum check?  A road-load air/fuel ratio check might indicate ethanol content being greater?  Idle scfrews need any tweaking toward "richer" for higher idle speeds?


It MIGHT be just that particular load of gas from the fuel terminal.  As almost everything is now "splash blended" at the terminal as the fuel goes into the tanker.  Unlike "back when" the oil company's OWN trucks delivered fuel from THEIR tank farms.


Have you pulled some fuel out and done an ethanol content test?   Is there an ethanol-free pump at the local Murphy Fuel location?


Of course, you can run that tank "out" quickly and put some more in.


Just some thoughts,


Link to post
Share on other sites
2 hours ago, JBP said:

(At what point do we tell Old Tank that we’ve been sneaking over and siphoning gas from his Century just to see if he’d notice and start blaming the car?) 😜

To avoid injury or death, turn your flashlight on when around the garage.  Then you can read the SIGN.

  • Like 1
  • Haha 6
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...