Paul wrote:
  "I sprung for a bottle of Chevron Techron.  It was the 1st time I've 
ever used it in my 79 bus.  I drove with it in a full tank, then refilled 
again today for the 2nd time since using it.  I thought I'd let you all 
know my city mpg has jumped up to *25*.  Before using the Techron, 
driving in stop/go traffic, I would only get 17 mpg.  .   .   .   .   . 
but the fuel economy has gotten MUCH better, wouldn't you say!"

  Paul, I don't want to rain on your parade, but you did ask.  Divide 25 
by 17 to see you're talking about a 47% improvement.  Ok, so I'm 
mentioning too many significant digits, but the order of magnitude cannot 
be caused by the bottled additive Chevron Techron.  I've chased 
incremental performance enhancements for many years, especially during 
the 17 years I competed in drag racing and briefly held national records. 
Now, I compete with my previous record of recorded mpg with each fill to 
the last penny top fill.  Synthetics like Mobil 1, Syntec, and Amzoil 
will give you a solid 2% mpg gain.
  I'm vexed by not being able to go back to an assured "pre treatment 
condition" on some of the "slick" products, but I'm very skeptical about 
whether or not they do any good.  I talked with one professional motor 
rebuilder who's rejected a warrantee claim on an engine that had an oil 
passage blocked with a bunch of this stuff.  You look at the performance 
of different oil filter brands tested to learn the threshold particulate 
size beyond which they won't pass (and they do vary) even when they are 
new and least restrictive, and you may question the idea that this stuff 
has enough time to "plate" the wear surfaces as claimed before it's just 
captured by your oil filter.  As to how this stuff could form a small oil 
passage block, I've no idea.  But at this point I'm pretty well convinced 
that it can happen.
  I've read every book I've encountered about how to improve milage, some 
by performance trials winners who share their techniques.  Lots of these 
tricks really work.  Perhaps you've pumped your tires up hard, gotten 
them aligned, are practicing fairly aggressive starts with super early 
shift points just above "lugging."  These work.  Perhaps you're not 
rushing to red lights like an idiot and started timing them for some 
reason, an engaging game when other drivers are eager to steal your 
safety margin space ahead.  Perhaps, the rigor of your measurements 
accounts for this.  I've run several vehicles with instantaneous mpg 
displays, and have one now.  Trust me, you cannot trust odometers, 
speedometers, or fuel tank gauges.  Interstate mile markers over minimum 
10 mile spans are useful and 100 miles are better with a stop watch, note 
pad and calculator.  Mechanical speedometers aren't even linear in their 
errors!  At least odometers are.  Fuel gauges can be calibrated by you, 
using your known mpg history and odometer observations after a fill to 
the last penny fill, but are useless in computing mpg.  When 
someone says "and it only took a quarter of a tank" it says a lot 
about them and little about fuel usage.  Carney operators look 
for fools like them every day.  Absolute fill to absolute fill is all 
that counts.  The auto pump shut off occurs at different points with the 
same pump on the same car.  My Lincoln Continental can take up to $3 
worth of additional diesel fuel after a pump automatically quits.  It 
varies a lot.  Try to factor that kind of variation into fuel consumption 
records.  It doesn't work.
  Sorry if this sounds like I'm trying to rupture your balloon, but I 
love efficiencey and if this stuff works as you describe, I'll become an 
eary adopter and happily post my apology for being too skeptical.
  Just to weigh in on the MPG poll, dropping insignificant digits to 
comply with the group norm, I've gotten as low as 27 mpg and as much as 
34 mpg with a '83 diesel Westie around town.  Florida is flat and I hate 
touching that brake peddle.  This is not the result of a casual effort, 
though I don't hold up traffic.    

	John Wakefield