"Larry Jaques" wrote in message
...
RCM only


On Fri, 18 Apr 2008 10:21:25 -0500, with neither quill nor qualm,
Ignoramus15242 quickly quoth:

I have a Chevy Silverado pickup that is by now about 18 months old.

I was never able to get more that about 220 miles out of a 22 gallon
tank of gas, sometimes even less.

However, the last three refills, gave me 280, 266, and 283 miles per
refill. (I usually run until my tanks gets fully empty, since I have
an emergency gas canister for the instance when I run out of gas).

This represents approximately 22% increase in MPG that I have hard
times explaining. I see three possible explanations.

1) Just before those refills, I did an oil change and used Mobil 1
synthetic oil. The previous oil changes were at a service station.

2) The engine had a chance to "burn in" and naturally improved its
efficiency

I am told (by friends who buy new vehicles often) that there is no
longer any break-in period necessary. One says that precision CNC
machining precludes that nowadays. Toyota asks that we vary our speed
during the first 1,000 miles, but that's it.


There's no break-in necessary to protect bearings, rings, etc. But there
still is a reduction in friction as the engine breaks in.




3) something is seriously mistaken in my measurements.

Are you using the same pump at the same station all the time? By law,
all filling station slabs have to be level, but "settling of contents
may occur during shipment."

Are you filling the tank or is a gas jockey doing it? Some allow the
tank to top itself, others pump in as much as they can possibly get.
The extra pumping might be your difference in at least one of those
calculations.

I need to put the fourth tankful in my new Tundra today and am
thinking about having that first oil change with a synthetic oil to
see if it makes any difference for me.


I am at a loss and am very puzzled. Can synthetic oil really account
for that much of an increase? I highly doubt it.

The wrong oil in really cold weather can make a difference, but this
is springtime. I doubt it, too.

--
The only difference between a rut and a grave...is in their dimensions.
-- Ellen Glasglow