Quote:
Originally Posted by wdb
Engineer you may be, but an economist you ain't.  That is misleading math you're doing there. What you want to determine is dollars per mile.
$per gallon, $2.49: divided by miles/gallon, 32: equals $0.078 per mile
$per gallon, $2.69: divided by miles/gallon, 34: equals $0.079 per mile
Not much difference -- or is it? Let's toss some miles in there so the numbers get bigger.
10,000 miles at $0.078 per mile equals $778.13
10,000 miles at $0.079 per mile equals $791.18
Still not much difference. The fact of the matter is that the cost of gasoline is a relatively small portion of the total cost per mile to drive a car. By far, depreciation is the greatest cost, followed by fixed costs such as insurance and maintenance. Next comes gas, followed very closely by interest on the car loan (if gas was $2/gallon, interest on the loan would be higher).
Bottom line: using the cost difference as a reason to use 87 octane instead of 93 octane doesn't really add up. And if you really, really want to save money on driving, buy old cars that don't depreciate and pay for them in cash.
It's already been shown that the Fit does indeed advance timing further when burning 93 octane than it does when burning 87. However the tests were performed at WOT, so there is still some question as to the benefit of higher octane under normal driving conditions. |
Yep.
You did the same math I did. Note that spending 8% more to gain 6% in mpg is a 2% loss; its is exactly the same as 778.13 vs 791.18 using your numbers. You just don't think saving a near tank's worth of refill per 10,000 miles is significant.
An economist says the $13.50 is significant because its money wasted. you didn't get your money's worth because you traveled only 12.64 miles per dollar instead of 12.85 miles.
If you were running a business thats very signicant. Again, its not the amount of difference its that you spend more than you get.
While gas is not the biggest portion of vehicle cost it is the largest of variable costs, the things I can do with my fleet that affect my costs. When I run 10 trucks at 5000 miles each per month, thats $67.50/mo (or $810 a year) I can put in profit that I wouldn't have. Add that to a hundred other things I kept careful tabs on amounted to probably $1000 per month my business didn't throw away. Or I had to charge my customers for unnecessarily. you need to sharpen your thinking on whats proper spending or I'll sic Clark Howard on you. LOL
Just where do you find the advance curves for Fits showing further advance when using premium? The ones run here shown them the same within one degree, our maximum margin of error. While there is a retarding program when spark knock is detected I find none that advances the curve when no spark knock is detected.