I bet the gas mileage and power is not as good as running premium! The
cost might not even be less if the gas mileage is significantly lower
with mid or regular gas. It's a good thing the TL will retard the
timing to prevent knock and save the engine from destruction.
It would be nice to know if it's worth the difference in price
between the gas grades. My guess, from experience with a different
car, is the difference in cost per mile would be small. Let us know
how much money your saving/loosing by using a lower grade of fuel then
what the manufacturer recommends.
I've run this experiment using my Sienna. I've run a number of
tankfuls of regular or premium fuel in succession so the engine
computer should have settled down. I've done this several times with
In town the car gets the same mpg whether I run the recommended octane
or 87. Seasonal/regional differences in fuel seem to make more
difference in mpg than octane rating. Last December (long highway
trips) I got 24-26 mpg on the highway outside cities vs. 22-23 when I
filled up in places where the pumps indicated a pollution-reducing
Fuel blend issues aside, on the highway the car gets slightly better
mpg with premium fuel; the mpg advantage grows with increasing speed;
I get very little benefit at 60 mph but a measurable 2 or 3 mpg better
at 70-75 mph. The harder the engine works (heavy load, mountain
driving, etc.) the more mpg premium delivers. On the other hand,
running at 60 mph is more fuel efficient than 75 mph so the most
economical way to drive is with 87 octane at slow speed. I've
recorded as high as 27 to 28 mpg (vs. EPA 23 mpg) on the highway
using premium fuel, cruising at 75 mph under very favorable conditions
(high plains, no traffic, Mobil 1 oil). And, no, I didn't try 60 mph
while driving across the plains.
Then again, if you drive your TL as if it were a minivan, perhaps
you're in the wrong car...:-)
I've not run similar experiments with my Corvette.
Well, Acura calls for 91 octane fuel. You could fill up with premium, (93
octane), run it down to half a tank, fill up with plus grade, (89 octane),
then run it down to half a tank again, fill up with premium, (93 octane),
and keep repeating this routine. You should end up with 91 octane, or close
to it, and that's what the manual calls for. However, you're only saving 10
cents a gal. for 8 or 9 gal. of gas every other time. Is that small savings
worth all the hassle?
Assuming I've done the math right of course. And you know the old saying
about "assuming" anything, right?
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