Everywhere gets two blends of fuels for winter and summer. Summer fuel
would not start well in the winter, and winter fuel would vapor lock in the
summer. Oxygenates are added in some areas in the winter to combat the
extra rich conditions associated with cold start and warm up. (Oct thru
April IIRC) I have read that oxygenated fuels do tend to give a little less
MPG.
I can tell you that different fuel will cause some cars to run different.
Back in the mid 1980s there was a large change in fuels, and the car make I
was working on had start and stall problems. Many of these could be fixed
just by getting the customer to switch brands.
If you still have doubts Google Top Tier gasoline and read the results.
Chevron was the first (and I believe) the only brand that did not have to
change its formulation to get this award.
However I doubt that any gas will make a difference in day to day driving.
If you drive long term on poor fuel, it could have a negative effect due to
plugged injectors, valve deposits etc. I suspect a case of confirmation
bias. The GOB bought the good fuel, so he drove a bit slowly, less jack
rabbit starts etc, and guess what? He got better mileage.
For my daily driver, I run Chevron, Shell, or Union 76.
$.02
Rick
On Sat, Apr 5, 2008 at 7:05 AM, Bob Spidell <bspidell@comcast.net> wrote:
>
> In CA, we get two different blends of fuel: "winter" and "summer." The
> winter fuel is blended for a higher vapor pressure and the summer
> blend--I believe--contains more oxygenates to help reduce smog (used to
> be MTBE, now probably ethanol). The summer blend will give somewhat
> lower mileage (maybe 1-2 highway mpg). Tire type and pressure probably
> makes a bigger difference.
>
> The GOB was BS'n.
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