Rick, that's fine.
One thing you have to be careful of is unscrupulous fuel dealers. It was touched on in an above post.
Some of the fuel dealers will add more alkie than 10%. This has been done in the past and weights and measure has been catching these people doing this.
If you suspect your getting lower MPG than you should I would suggest you talk to your local weights and measure people. I work just down the hall from these people in the same building and have used their services once. Your fuel dealer may be putting more alkie in the mix to make a bigger profit. :M
Once I though I was getting screwed on octane. W&M immediately pulled a sample and checked it. It was too spec.
The guy that runs the department just told me in the 13 years he has worked for W&M they only caught one sample that was low on octane. I don't know if they check for alkie content?
Maybe something to check into if you're getting much below 4 to 5% in fuel mileage with E10?