Better MPG on 87 vs 89 gas?

In an act of financial desperation, needed gas and no money, I put Chevron 87 vs 89 and got a bit better MPG. Why?

 

Probably different driving conditions, you would have to run several tanks of each to see if there is any difference at all.

 

Same all. For ever have used only Chevron 89. Usually I get 18.8 in morning traffic mixed city and freeway at 35-45 MPH. Today I got 22.3 MPG Why, Why???

 

Probably just a fluke to be honest. There is very little to zero evidence that different octane fuels do anything for trucks like ours.

Could have had a tailwind, traffic was a little better, etc. Did you use the pumps at your "regular" gas station? I only ask because in Utah the last few months it was they were using winter gas and southern Utah was using summer gas. Slightly more energy density in the summer blend. Plus air density of colder weather...nevermind, it was a fluke.

 

87 is what is recommended

 

NA vehicles are different from FI when it comes to octane requirements. Lower octane fuels tend (TEND) to burn quicker than higher octane, which can give a bit more oomph, especially when combined with a high compresion ratio like our trucks have. However, I'd go with the fluke option, combined with warm weather. Warmer=better fuel economy.

 

Fluke. The gas wouldn't make THAT much of a difference, if anything 87 octane would get you like 3% better mpg because thats approximately how much more energy 87 octane has over 89. Lower octane gas actually has HIGHER energy density (kinda counter intuitive).

BTW the tacoma is tuned for 87 octane you're getting no value running 89. You'd be better served making sure you use QUALITY 87 octane like Shell or Chevron vs generic gas stations which will in general use lower guality detergents and gasoline.

 

I make the same 20 Mile drive frequently and the MPG for that trip varies from 20-23, has nothing to do with fuel but more with temperature and weather differences.

 

how are you calculating mileage? Trip miles on the odometer vs gallons pumped? My money is you forgot to reset the trip meter.

Plus what @Jaque8 and @shakerhood said.

 

For a very long time I have used Chevron 89 from the same station and most of the time same pump. I needed a bit of gas to make till today (payday) and used 87 since cheaper. I drove the same route every day in the same traffic conditions and the MPG are almost (+/- 1%) identical. Each time at fill up I reset the trip odometer and MPG reading deleting all present and past records.
Should I stay with 87 or continue with 89??? Will put a full tank of 87 today and for 2 weeks will monitor results if the same or better with 87 vs 89 since I know the MPG for 89.

 

Well I'm guessing since you barely have money for gas you're being extra conscious with your driving and throttling leading to increased MPG.

 

Dacon, meet small sample size. Small sample size... Dacon.

 

Keep in mind the Octane rating is a MINIMUM. It is fairly common in the gas/fuel station industry for them to actually have 90-93 rated fuel dropped into the 87 or 89 tanks. A lot of it has to do with availability and how the service station is run.

 

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Confused...If 87 has more energy than 89 or 91, why sport cars require 91/93 for performance?

 

High compression. Higher octane is better to prevent knocking/pinging.

I put 85 octane in. This is what is considered Regular in high elevation states. No difference with higher octane gas.

 

I used only 87 and I average 21 to 22's each tank. In the winter it drops a bit, but not much.

 

Summer blend and you made a lot of green lights. Summer blend good for 1 to 2 mpg easy .

 

Thats why I said its kind of counter intuitive.

In simple terms octane is just to rate fuel by point of self ignition due to pressure. Higher octane fuels can handle higher pressure (compression) before self combustion. If you put a low octane fuel in a high compression engine the fuel ignite due to pressure BEFORE its supposed to (before the spark), this leads to pinging/knocking/pre-detonation.

High compression performance engines will create more power with less energy dense fuel because they are high compression themselves and are tuned accordingly. Theoretically if you could put a lower octane rating in a turbo motor without retarding the timing you would have a very minimal increase in power due to the higher energy density, but the increase would be negligible.

 

Are out trucks high or low compression engines? Better suited for low or high octane gas?
(I am ignoring all I know and looking for an educated explanation)

 

My 2 cents:

I owned an 09 2.7L Taco for 5 years, and now a 16 3.5L for the past 5 months. Both of them came with a full tank of gas when I bought them...87 octane. Maybe it is all in my head, but I could feel the slightest stumble/hesitation in accel off idle. Both trucks did it. Depleted the 87 octane until gas light, filled with 89 octane, within a few mins of flushing the fuel through the system, that stumble/hesitation was gone. I know at least on Tundras with a 5.7L, toyota has low/high octane spark table within their tune. I am not sure if this is the same for everything, or if tacos even come with the sensors necessary to measure octane, but I swear that 89 octane, even in my 2.7L, helped with drive-ability.

I never saw much of a difference in MPG. The truck just felt better, especially off idle.

P.S. 99% of the time I end up at Chevron