When I drove Millicent home 600 miles from the school district, I recorded 9,5 MPG. This last trip, close to the same distance in similar terrain, we recorded 13 MPG. Is that possible, or are we filling the tank unevenly?
That glorious day in December 2006, Millicent had...
Cracked fuel hoses, drawing air into the fuel.
Old motor oil.
Old "regular" tires with unknown pressures (although they looked inflated).
And she had just plain sat parked a couple of years, except for one recent short drive.
And she may not have been up to 55 MPH... ever.
It was December; cool weather.
Last weekend, we had...
Good fuel hoses.
Synthetic motor oil.
New "low-profile" tires.
And she has seen more regular use, specially long trips at 55-57 MPH.
It was June; hot weather.
On the downside, she now carries 16 square feet more frontal area, and pulls a trailer.
The old fuel would have been gradually replaced with fresh fuel on the original drive home, and I remember being pleased that they sold her with more than half a tank. Maybe she got just a couple of MPG those first couple hundred miles on the two year old fuel?
I know the fuel hoses drew air, because I had a starting problem that went away when I replaced the hoses. Air in the fuel may have led to less power, but I don't quite see how that would affect milage.
Old motor oil is a known problem. When I change the oil in my Dodge Dakota, it immedidately feels like I have more power. So fresh, and full synthetic, oil is bound to help some. But 30%?
New tires generally yield worse milage, because of more squirming in all that rubber. But the modern "lo-pros" like we use on the 18-wheelers at work, may have an advantage in casing design.
"Blowing out the cobwebs" will probably help a little -- re-breaking-in parts that have sat and oxydized in that old oil in a humid climate for a couple of years.
What might the change in ambient, and fuel, temperature have done to fuel milage? Less power, yes. But milage?
Aerodynamics: The 20% increase in frontal area is bound to hurt. The trailer may not have had any negative effect -- heck, it may even have helped, aerodynamically.
Thoughts? Facts? Superstitions?