You wrote:
As we got to higher elevations I noticed the
regular gasoline octane rating went from 87 (here in TX) to 86 then 85
in the mountains. Premium octane ratings declined from 91 to 89
I got to wondering why this was. I was thinking it might have something
to do with altitude, and lower octane being OK.
Yep, you're bang on. As the altitude goes up, the air pressure goes
down, and so does the effective air pressure inside a cylinder.
Essentially, high altitude lowers compression. In the old days when
trucks were naturally aspirated gas engines, you could order
"high-altitude heads" that were higher compression, to make up for
the air density loss due to altitude.
--
Dan Weeks
Freelance Writing and Photography
515/279-4825
[EMAIL PROTECTED]
