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Discussion Starter #1
Purpose: I've been somewhat frustrated with my measley 14.5 mpg... considering I have a 2wd RCSB 4.8 and I don't drive "agressively". For the hell of it, I decided to see if it would pay off in the end to run 89 octane fuel, instead of 87 octane. I wanted to see how much my mileage would increase, if any.

Hypothesis: My truck will see slightly better performance and mileage, but the extra cost of fuel will not offset these gains.

Methods: I bought 89 octane gas at a price of $3.00 per gallon. This was 10 cents more than 87 octane gas, at the same station. I drive extactly the same places every day and every week: my school schedule, work schedule, gym schedule, volunteer schedule, etc. don't change. Therefore, I drove in very similar traffic, at similar times, and even at similar temperatures, using the same route as always.

Results: After 13 days of driving on 89 octane gas, it was time to fill back up. I saw an increase of exactly 1mpg using the 89 octane gas. It increased from an average of 14.5mpg to 15.5mpg. OK, so I saw a decent increase (not to mention my engine probably likes 89 better than 87), but did this increase offset the extra cost of the gas???

Conclusion: YES!!! It is actually cheaper to buy 89 octane gas than 87 octane gas. (Calculations may be seen below:)

87 octane:
24 gallons x 14.5mpg = 348 miles per tank
$2.90 x 24 gallons = $69.60

348 miles / $69.60 = 4.14 miles per $1 spent

89 octane:
24 gallons x 15.5mpg = 372 miles per tank
$3.00 x 24 gallons = $72.00

372 miles / $72.00 = 4.3 miles per $1 spent

So, for every $1 I spend at the pump, I can go an extra 0.16 miles! I spend about $140 on gas monthly, so about $1680 per year: that equals an extra 268.8 miles for FREE... just by switching to 89 octane.




Sources of error: This is only true if the price difference between 87 and 89 is about 10 cents or less. Also, I have not taken an average mileage using 89. (This was only based on 1 tank of gas.) Also, the cheaper the overall price of the gas is, the less you will save by switching. The more expensive the overall price of the gas is, the more you will save by switching. (If the difference between the two prices is about 10 cents or less.)




Please critique my study or find another source of error. :crazy:
 

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Giggity Giggity Giggity
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Were the weather conditions about the same? I increased my timing and fueling with hp tuners to where I need 93 so it won't knock. I backed off on the timing a little and drive less aggressively so I can run 89. Sounds like your "experiment" is a pretty good idea though. I need to try it out myself.
 

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Discussion Starter #3
The weather was about the same. I've had my truck since October and I've been getting 14.5mpg consistently. The temperature highs ranged was from 28 degrees in December to 60-75 degrees last October. The temp didn't seem to affect the 87 octane mileage.

The temperature was between 60-75 when I used the 89 octane. (About 5 degrees warmer than the last tank I used 87 octane on.)
 

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Giggity Giggity Giggity
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Oh ok; sounds like a pretty controlled experiment then. Looks like you got all the bases covered.
 

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why not just get a tune to bump it up 2.5 more mpg
 

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Cool :shake:. I get 14.5 mpg in my 01 5.3 34.5"s 3.42's:pow:. I'm hoping regearing will bump me up over 15. I may try 89...


"I'm fittin to go try dis at home":jester:
 

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Discussion Starter #9
was this just over 1 tank? run 89 for several tanks and see what you get.
Yes, just one tank. I'm going to run it in a few more tanks to see what I get, and get a good average going. It's getting warmer though and I'll probably start having to use my A/C. That will somewhat hurt my mileage.

why not just get a tune to bump it up 2.5 more mpg
I want to... I might have JustinSS (I think that's his name) tune my truck, the next time we're all at a meet.
 

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89 yielded slightly better MPG in my '00 Tundra with the 4.7L V8. It saw 13.5 on a good day, on stock tires.

HP/MPG ratios on these small V8s sucks :imo
 

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Yes, just one tank. I'm going to run it in a few more tanks to see what I get, and get a good average going. It's getting warmer though and I'll probably start having to use my A/C. That will somewhat hurt my mileage.


I want to... I might have JustinSS (I think that's his name) tune my truck, the next time we're all at a meet.
are you coming to the Cen Cal meet on april the 7th?
 

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higher octane should result in better gas mileage because it burns slower and more efficiently, I run 91 all the time. I have 95 and 100 available to me at a local station for when I go to to the track too.
 

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I have also noticed a slightly better gas mileage by using "mid-grade" gas. But, it can tend to be 0.15 to $0.17 more expensive here. About three years ago, there was a gas station here where mid-grade cost $0.02 more...the good old days.
 

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samcarol
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I have also noticed a slightly better gas mileage by using "mid-grade" gas. But, it can tend to be 0.15 to $0.17 more expensive here. About three years ago, there was a gas station here where mid-grade cost $0.02 more...the good old days.
I remember when gas broke the 1 dollar mark and it was a huge deal. If it ever got that low again, I would never stop driving.
 

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I remember when gas broke the 1 dollar mark and it was a huge deal. If it ever got that low again, I would never stop driving.

Boy, if gas cost a dollar...I'd get a tanker of it, a drum of fuel stabilizer and wait :evil:
 

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Have you ever googled "octane myths"?

The power output of an engine depends on the energy content of its fuel, and this bears no simple relationship to the octane rating. A common myth amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this is false—engines perform best when using fuel with the octane rating they were designed for and any increase in performance by using a fuel with a different octane rating is minimal or even imaginary.
http://en.wikipedia.org/wiki/Octane_rating

Another myth is that use of a high octane fuel will improve fuel economy. The fact is that fuel economy is determined by a number of variables, including the energy content of the fuel and the condition of your vehicle, neither one of which have anything to do with the octane level of the fuel. In fact, two fuels of identical octane could have different energy content due to a difference in composition.
http://www.co.suffolk.ny.us/webtemp3.cfm?dept=3&id=2049

High octane gasoline improves mileage.
In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve mileage. If switching to high octane gasoline does improve mileage, you might find that a tune-up will give you the same improvement on 87 octane gasoline.
http://www.state.mn.us/portal/mn/jsp/content.do?test=y&id=-536881350&subchannel=null&sc2=null&sc3=null&contentid=536884591&contenttype=EDITORIAL&programid=536884577&agency=Commerce

You should use the minimum pump octane (AKI) fuel that will run in your engine without knocking. You're wasting your money on higher octane fuels if there aren't needed to control knock. The two most common myths regarding pump octane (AKI) are that it will increase performance, and result in better fuel mileage.
http://www.ibmwr.org/otech/octane.html
 

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I CANT SPELL GET OVER IT
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shit i remember when i was in High school gas coast $00.87
 
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