Rafi,

It is my recollection that the oxygenated fuel will yield better emmissions which is the whole reason that they require its use during the winter. Cold weather makes the engine more polluting, especially during the warm up period - which of course is longer in January than July - adding the oxygenating additives helps to counterbalence this.

You will notice poorer fuel economy as measured in miles per gallon however since less of what goes into your tank is the actual fuel that powers the car. You're also getting some oxidants which during the summer come entirely from the air.

jlc

__________________
Jeff

'87 560SEL 267K (177K on motor) Blue/Blue
'98 Buick LeSebre 60K (wife's car)
'56 Imperial Sedan 124K
Past Cars:
'67 Dodge Monaco 130K (Sold)
'87 Chrysler 5th Ave 245K and going strong (sold)
'73 Plymouth Satillite 175K (sold)
'96 Chrysler LHS 80K (totaled)