Now for the arguing of the disbelievers~!
I advanced my timing to 16 degrees from 8 degrees factory spec's then the carb was already leaned out, because the RV lives half the year at 7,200 ft elevation in Flagstaff, Az...Then I go down for the winters to Lake Havasu, Yuma, or Quartzite, which is about 800ft above sea level...With the carb already leaned out I did my test with the advance already done..I went from 8 miles a gallon with detonation to 16 miles a gallon running water methanol mix. The mix I use is one 12 once bottle of HEAT in the Yellow bottle to one gallon of water which is about a 33% mix(pure methanol) not the ISO-Heat which is Isopropyl or rubbing alcohol ~!
I tested this 3 different times on a full tank of 32 miles. In all cases, I went from 8 miles a gallon to 16 miles a gallon.. Then I tried it up the mountains driving from Quartzite, Az. to Lake Havasu for a total of 72 miles; Again, 16 miles a gallon...In the 2-1/2 gallon plastic kerosene jug I use for the mix, I have now filled it a second time since last November...It sips it into the vacuum port at the base of the carb.