Gas mileage vs Octane...
Thread Starter
3rd Gear Member
Joined: Apr 2007
Posts: 763
From: Pa
Gas mileage vs Octane...
I know I am opening pandora's box on this one... but I'm going to put this out there anyway.
I've seen alot of posts asking about performance gains of 91 or 93 octane vs 87. Like everyone else, I will say that there is no gain in power to be had simply by going to a higher octane fuel without tuning for it. However, after 10,000 miles of tracking the gas mileage onmy stang, I can say for me, with my driving habits, there is a slight mileage benefit to it, enough so that that good gas is slightly cheaper to run than the cheap gas.
Now, I haven't even posted this yet and I can already see the BS flags coming up and people telling me I need to check my math or get a new calculator, so I will post the math up here. I track my mileage religiously because I get reimbursed for fuel and mileage with my work, so the cheaper my drive is, the move money I make from it. I do not use the computer in the car (mine doesn't even have it), and I always fill the tank at the same pump and I operate it myself, so the filling technique is the same. The mileage is only when I am doing all highway miles and the only city driving is the 3 miles from my house to the highway. I cruise at 70 mph with the cruise control on. The C&L went on prior to me watching my mileage this closely. AC on or windows down is pretty much a wash, and the only real variable in the mileage is how hard I blast out of toll booths and through on ramps. So.. here's the numbers I have found:
I get between 20.3 and 20.6 MPG when I run 87 octane, which we will average at 20.4 for the math.
I get between 23.4 and 23.8 MPG when I run 93 octane, which we will average at 23.6 for the math.
Typical fill up is around 11 gallons for me, because I rarely run it down too much passed 1/4 tank.
20.4 mpg X 11 gallons: 224.4 miles between fillups.
23.6 mpg X 11 gallons: 259.6 miles between fillups.
The station I use (as of today anyway) 87 costs $2.53 a gallon, 93 is $2.81
2.53 a gallon X 11 gallons: $27.83 a tank
2.81 a gallon X 11 gallons: $30.91 a tank
$27.83 to fill up / 224.4 miles per fillup: 12.40 cents per mile in fuel cost
$30.91 to fill up / 259.6 miles per fillup: 11.91 cents per mile in fuel cost
And to take it one set further to make it apples to apples; to go 224.4 miles and refill with the 93, would cost 26.73 to fill up again... which works out to $1.10 a tank cheaper to go the same distance.
Now, if you are running cheap gas now, and run out with your next fillup and expect a huge jump in MPG, your not going to see it. It takes time for the engine to learn that it has good gas and can run a slight bit leaner and with slightly more timing to see these numbers. I would think on the order of 5 to 7 tanks might get you a good decent increase, maybe faster if you disconnect the battery on your car and let the computer reset.
Now, I am not saying that you should all go and run only the good gas. I'm not even saying that your mileage will match mine exactly.But I certainly think that if mileage or fuel costs area concern to you at all, this may be something to consider. Try it and see how it works out for you.
*Flame suit on*
I've seen alot of posts asking about performance gains of 91 or 93 octane vs 87. Like everyone else, I will say that there is no gain in power to be had simply by going to a higher octane fuel without tuning for it. However, after 10,000 miles of tracking the gas mileage onmy stang, I can say for me, with my driving habits, there is a slight mileage benefit to it, enough so that that good gas is slightly cheaper to run than the cheap gas.
Now, I haven't even posted this yet and I can already see the BS flags coming up and people telling me I need to check my math or get a new calculator, so I will post the math up here. I track my mileage religiously because I get reimbursed for fuel and mileage with my work, so the cheaper my drive is, the move money I make from it. I do not use the computer in the car (mine doesn't even have it), and I always fill the tank at the same pump and I operate it myself, so the filling technique is the same. The mileage is only when I am doing all highway miles and the only city driving is the 3 miles from my house to the highway. I cruise at 70 mph with the cruise control on. The C&L went on prior to me watching my mileage this closely. AC on or windows down is pretty much a wash, and the only real variable in the mileage is how hard I blast out of toll booths and through on ramps. So.. here's the numbers I have found:
I get between 20.3 and 20.6 MPG when I run 87 octane, which we will average at 20.4 for the math.
I get between 23.4 and 23.8 MPG when I run 93 octane, which we will average at 23.6 for the math.
Typical fill up is around 11 gallons for me, because I rarely run it down too much passed 1/4 tank.
20.4 mpg X 11 gallons: 224.4 miles between fillups.
23.6 mpg X 11 gallons: 259.6 miles between fillups.
The station I use (as of today anyway) 87 costs $2.53 a gallon, 93 is $2.81
2.53 a gallon X 11 gallons: $27.83 a tank
2.81 a gallon X 11 gallons: $30.91 a tank
$27.83 to fill up / 224.4 miles per fillup: 12.40 cents per mile in fuel cost
$30.91 to fill up / 259.6 miles per fillup: 11.91 cents per mile in fuel cost
And to take it one set further to make it apples to apples; to go 224.4 miles and refill with the 93, would cost 26.73 to fill up again... which works out to $1.10 a tank cheaper to go the same distance.
Now, if you are running cheap gas now, and run out with your next fillup and expect a huge jump in MPG, your not going to see it. It takes time for the engine to learn that it has good gas and can run a slight bit leaner and with slightly more timing to see these numbers. I would think on the order of 5 to 7 tanks might get you a good decent increase, maybe faster if you disconnect the battery on your car and let the computer reset.
Now, I am not saying that you should all go and run only the good gas. I'm not even saying that your mileage will match mine exactly.But I certainly think that if mileage or fuel costs area concern to you at all, this may be something to consider. Try it and see how it works out for you.
*Flame suit on*
Thread
Thread Starter
Forum
Replies
Last Post
Matt's 95 Stang
5.0L (1979-1995) Mustang
2
Oct 5, 2015 07:16 AM
