wrote:

>>Using full syn oil gives me another 2 >mpg

>some m p g might be gained by using synthetic oil (speculative) in fact
>some synthetic oil "blenders" label their oil as doing so.

>but the best mileage increase that I have ever had was with Arco
>Graphite motor oil, w/a conventional oil base (since discontinued). this
>oil had everything going for it, but never become a mass buyer's item,
>what a shame..

>Royal Purple synthetic motor oil is touted as being a real quality motor
>oil with friction fighting additive pkg. - that adds more m p g.

Back in the late 1970s, Exxon and ARCO claimed their Uniflo and
ARCOgraphite oils provided 4.5% better fuel economy, but in the past 20
years no major oil companies have made similar claims, except to label
their oils EC (energy conserving), which means they provide an economy
improvement of 0.5-1.4% (depends on viscosity range) over non-EC oils.
There was also an older designation, EC-II, to indicate a 2.7%
improvement, but I believe it's obsolete and not comparable to current
EC ratings.

I used ARCOgraphite in a Dodge Dart Slant Six from the time the oil was
first put on the market until it could be found only at Chrysler
dealers. My oil analysis metal wear numbers were always low, and I
found no varnish under the valve cover as I had with ordinary SF-rated
oil. My gas mileage rose from 21-23 MPG to 24-25 MPG, but I suspect
much of that was due to switching over to radial tires (not standard
equipment when the car was bought), which reduce rolling friction by
approximately 1/3 over bias tires.