Re: Mileage Report
- Ok, but your though goes out the window when the 89 octane E10 is the SAME price as the non-E10 87 octane at the other stations.
A far as Walmart, I have bought some Walmart gas and it's just as good as any other. However, some are junk. I regularly make a trip to Iowa and there is one Walmart that has great gas and I buy there when the price is right. Same with one semi-local Walmart. OTOH, another Walmart along the route is trash! No way will I ever buy there again.
I just made another highway trip, with less highway, and gobs of headwind and got 47 MPG, better than normal for that trip, and using the E10. Read the owners manual. They recommend E10 over other fuels. At least the 2007 manual does.
--- In firstname.lastname@example.org, David Kelly <dkelly@...> wrote:
> On Jun 30, 2013, at 7:04 PM, Chris Wells <radioactive55man@...> wrote:
> > Yes 87 versus 89 octane.
> > All modern gas cars have knock sensors and adjust the spark advance to
> > compensate for the octane.
> > Lower octane = less advance=less burn time = less mileage.
> > If with 87 octane you get no knock at maximum advance then going to 89 is a
> > waste.
> Thats the shade tree mechanic's definition of what is happening. Usually its close enough. The problem with such a definition is when experiment fails to prove any difference yet one continues because they believe their "science is settled." Everyone is told 97% of all mechanics (shade tree or not) agree so it must be true. :-(
> Not only that but the operating conditions and controls on the Prius's Atkinson Cycle engine can throw a lot of rule-of-thumb out the window.
> Chris got it right the first time but perhaps didn't realize it. If $0.10/gallon more gets one from 48 MPG to 52 MPG then that is all that matters. 48 MPG at $3.50/gallon is $0.073/mile and 52 MPG at $3.60/gallon is $0.0692/mile. It doesn't really matter why the gasoline labeled 89 octane works, it works.
> For advancing from 48 to 52 MPG at $3.50 for 87 octane one could pay $3.79 for 52 MPG fuel and still break even. But I would caution that its pretty hard to consistently measure MPG to that precision with a Prius. Must average many tanks for any precision.
> Around here $0.20/gallon is the usual price step from 87 to 89, and another $0.20 to get from 89 to 91 but sometimes will go all the way to 93.
> I suspect Chris won't find the same results comparing other fuel sources. Locally I find the least expensive Sam's Club gasoline to be as good as the most expensive local brand, Shell. One would think Murphy Oil Co (Walmart) to be the same as Sam's but its as bad as Kangaroo/Cowboy. Exxon's 87 also used to be pretty bad, just about exactly as bad as Chris found between 87 and 89 at one gas station.
> So in short don't everyone go out and start buying 89 octane and pat themselves on the back trusting higher MPG and lower operating costs. By all means try it. But verify. And don't atop verifying.
> David Kelly N4HHE, dkelly@...
> Whom computers would destroy, they must first drive mad.
- Driving conditions make a big difference in fuel efficency - especially with the Prius and especially if you know some hypermiling tricks.
Sofar in over three years of driving my overall fuel efficiency calculated has been from 44 to 71 mpg depending on the overall driving conditions.
My (Scangauge2) fuel efficiency estimates per trip has vary even wider from about 11 mpg to 132 mpg depending on the driving conditions.
The Prius' HSI display fuel efficiency display estimates more optimistic .
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