Can you say "Winter Blend"?

 

i get about the same.^^^^^^^^^^^^^^^^^^^^^^^^^+1 kc9jvc

 

if it happened close after changing sparkplugs
there might be one defective sparkplug out of the new 8
as 7/8 ths of 15 is about the 13 MPG you are now finding,
about 2 MPG less

 

Its the gas, every time we switch from summer to winter blend it cause the mpg to drop, add that in with cooler weather and you can expect the mpgs to drop a little, and 2mpgs is a little bit specially based on the computer. Mine changes that much on a monthly basis going off the computer readings, it also will change if I do alot of highway vs city driving too. Do a pen and paper hand calc to find your real numbers, you sohuld see less of a drop over a few tanks and it will give a much better average.

 

i read my manual and reset my overhead today and the mpgs rose from 11.5 to 12.3, so im pretty happy.

 

summer and winter blends of gasoline do officially vary:

http://www.epa.gov/orcdizux/rfgecon.htm

the only way the DIY owner can find out with some accuracy
if their vehicle is 'sick'
is to have done summer and winter
steady 60 mph MPG tests over 100 to 300 miles
ahead of time
that they can compare to

the steady 60 mph test runs for MPG
will also 'open your eyes'
to what surprisingly good MPG
a Ram pickup can do

 

If he has a defective plug, wouldn't he notice a miss?

 

yeap

typically ~%10 drop

we're all feeling it

 

alot of the gas companys are using the 10% ethanol now and that does make a huge difference i tried using it since i could use the 87 instead of 89 because of the ethanol in it and i saw a difference of about -3mpg so i would say check the pump and see if thats what you are getting now, I'm from the south so there is no winter gas here so i can't comment on that.

 

the ability to detect a miss varies

this is not helped by the
Magnum 5.9V8's typical rough idle
even when everything is up to perfect factory specs