Testing Octane Fuel Brands: Performance, Volitility, gas mileage

[Bigvinnie]

I own a 2004 Nissan Frontier with VG33e. Recently I started a new career in construction management for a very high quality solar company. Lately I've been comuting as far as Fresno, California, and back to my home in Concord.Since I get payed mileage per diem I've decided to do tests on my Nissan Frontier, and compare gas pricing to performance, mileage and volitility using all different octane grades and brands of gasoline. Now although the Nissan owners manual recomends 91AKI, that doesn't mean that the engine won't run on lower grade gasolines, making it possibly suseptible to KNOCK and PING. The VG is a very durable engine using a Hemispherical head design, with single overhead cams.My engine is slightly modified with a K&N drop in filter, and a magnaflow 2" dual exhaust system from cat backs(making it a true dual exhaust).

Down side to my truck is that it is a work truck with a lumber rack with a weight of 400LB.s, a tool box with tools adding an additional 150LB's.So I am daly towing 550LB.s which severly drags on my gas mileage, not to mention I weigh 245LB.s as well. Total towing weight daly is 795LB.s......It hasn't had an electrical tune up (plugs, wires, rotor) since I bought the vehicle. It now has 53,000 miles on it.The test I performed was daily driving conditions, using the air conditioner for atleast 1/2 of the driving trip/distance, driving in 90* weather conditions, and maintaining a AVG freeway speed of 78MPH.I filled all fuel tank fills to the top before each test and drove the truck until the engine would sputter and run on fumes. I carried a 1 gallon gas can unless I was to stall on the freeway.gas tank is calced to hold 17.2 gallons, but beeing that I could make it to the gas station on fumes I've lowered the amount consumed to 16.9 gallons on average.

So lets begin with fuels I've tested and what it's rating and price is. I will list additional passenger weight for trips commuted since this adds to load and towing which would consume more fuel....

FUEL TESTED1.) Quick Stop fuel Grade Fuel: 87 Octane Volitility: High Cost:$3.47 per 9/10gallon Mileage driven:318.8Miles MPG:18.86 Added Passenger weight:0 (total towing weight 795LB.s)2.)chevron with techron Supreme Grade Fuel: 91 Octane Volitility: low Cost:$3.76 per 9/10gallon Mileage driven:326.6Miles MPG:19.325 Added Passenger weight:220 (total towing weight 1015LB.s)

So far what I have concluded from this test is that supreme fuel is defenitely better for overall towing. But over the .29 cents per gallon cost it is not effective enough as a cost saving comparison, in a world where gas prices are overinflated. Cost difference between regular and supreme is 29centsX17gallons=$4.93 cost difference. You could spend that $4.93 on an addirional gallon of regular and still get more mileage per cost comparison than you could on 91Octane and still walk away with a $1.30 on average. Or you could purchase 89 octane and break even with your price budget, towing capacity, and MPG.

I will update this thread at the end of the month with more comparisons if people are interested.


Modified by Bigvinnie at 4:27 PM 11/20/2008

[Q45tech]

What really counts is BTU per gallon, as the higher the btu the higher the pressure......................study historicals of gasoline before oxygenates were added , before the EPA required reduced aromatics and allow the thinning of gasoline to allow more from a barrel of oil.Doesn't work with diesel why MPG is superior.

http://www.nafa.org/Template.c...lentsh ... fgecon.htm

In 1995 gasoline was 124,000 BTU per gallon today you are lucky to find 111,000....................magically it lost 10% when we increased number of gallons per oil barrel by 10%

[Bigvinnie]

What really counts is BTU per gallon, as the higher the btu the higher the pressure......................study historicals of gasoline before oxygenates were added , before the EPA required reduced aromatics and allow the thinning of gasoline to allow more from a barrel of oil.Doesn't work with diesel why MPG is superior.

http://www.nafa.org/Template.c...lentsh ... fgecon.htm

In 1995 gasoline was 124,000 BTU per gallon today you are lucky to find 111,000....................magically it lost 10% when we increased number of gallons per oil barrel by 10%

You can also add xylene which is an actuall aromatic added to fuel. My understanding is that it is a really high MON octane, with a high Kj burn off as well, good substitute for power, bad on the enviornment though. Not to mention a gallon of xylene will cost almost $20, unless of coarse you buy it in bulk at contractor supply stores.Another reason why gasoline of today is so low on power is it's mixture with ethanol which is roughly in the 10% range added to all street gas. MTBE was a good source of power until we found out it wasn't as enviornmentally friendly as we thought it was.

What really sucks about todays more modern fuel compared to fuel sold around 20years ago, is it's high volatility to ambient air temprature... Since the fuel of today has a lower BTU, or KiloJoule burn rate it expands and vaporizes faster. So lets say you drive around on a hot summer day that is in the mid 90* F, your engine will make on average 10HP less on AVG, than driving in a mildly 70*F spring day....

Really this hole enviornmentally friendly thing on making fuels cleaner is only making us consume oil faster. Whats worse pumping oil faster out of the ground at an alarming rate, or crossing our fingers that the Ozone is causing this green house effect.

Really engines are so technologically advanced we should go back to when catylitic converters and EGR's were non existant. Then we would have cars producing roughly 60miles per gallon with todays engines. using less gas that we would pump out of the ground. It takes energy to make energy. So the catylitic process through back pressure consumes engine power like a leach, not to mention we are using fuels that are less in energy.....

Sorry I had to ramble..

[CT_Maxima]

I have a 4.0 liter '06 Frontier and have found higher octane is better for mpg and power. The economics depends on the offset between 87 octane and premium. At Costco, where I buy my gas, this offset varies from $0.15 to 0.30 per gallon. I know at the lower number, the economics are good. I have to re-run the numbers for the $0.30.

[Bigvinnie]

Woot!!!!! Price of gas is going down!!! Stock market speculators claim that regular will be as low as $3.00 by this november!!!!! Going back on 91 octane!!!!!!!

[Bigvinnie]

UPDATE:

O.K so it's been a little over a month since my last post.

Since then I did a full 60,000 mile electrical tune up. NGK claims more power and better fuel economy using there iridium brand plugs over the standard plugs. So I thought to myself why not. So I went out and spent $12.00 a plug over the standard $3.00 platinum plugs that are used for my VG33e.

What I purchased were the NGK Laser Iridium plugs. I also purchased a new rotor and cap, as well as autolite wires. The iridiums are part IFR5E11, the original plugs recomended by the manufacturer are the NGK platinum part PFR5G11. Now the iridium plugs are direct bolt in there is no gapping of the plug at all and infact if you try to gap the plug it will not be covered under manufacturer warranty for defect.

So after doing the full electrical tune up, I double checked my tire pressure. My rear tires are 35PSI rear and 30PSI front.

The challenge was to see if I could achieve more gas mileage under almost the same driving conditions, and load that my truck usually has in weight from the first test taken in this thread.

A few changes were made though, first thing was my AVERAGE freeway speed was reduced to 70MPH, instead of 78MPH from the first test. Ambient air temprature is within 70* rather than the 90* recorded from the last test. I also used the air conditioner 2/3 less than previously recorded. I compensated for more city driving, which was 50% of this road trip.Towing remains the same at 795LB.s. Oil is old and remains unchanged at 3100 miles, (the added viscosity actually effects gas mileage).

FUEL TESTEDUSA gasolineGrade Fuel: 91 OctaneVolitility: lowCost:$2.39 per 9/10gallonMileage driven:340.1Miles MPG: 20.12 MPG

So compared to the previous test using chevron with techron. My engine gained .799 MPG, Thats over 2/3 MPG gained since previous test.

Next up is my mission to install electric fans and a KA24e thermostat, to see if my engine can achieve over 22MPG!


Modified by Bigvinnie at 9:02 AM 11/21/2008