Better MPG on 87 vs 89 gas?

I think we are mostly fixated in the way the gas is manufactured (which is almost the same across brands) but the noticeable difference may be due to factors outside the manufacturing and initial storage process. I guess the main question is what is the cheapest gas( cost you the least annually) that would allow your truck to function properly without any adverse affects. Keep in mind that going from 87 to 89 octane driving the same miles per year( 15,000 per year, filling the tank like once a week) and getting 0.5 to 2.0 better MPG will save $2.00 to maybe $7.00 per tank (or around $100 to $300 per year )depending on the price difference between 87 and 89 octane.

 

Because you actually drove it like a truck instead of a sports car. lol JK iono

 

http://www.appropedia.org/Energy_content_of_fuels

Again I wasn't claiming its significant but for sure on a technical level higher octane = lower energy density, its just science man

Look at diesel fuel vs aviation gas for it to really start becoming apparent. Also the energy density of gas even varies from brand to brand! They all use different additives and detergents that have various octane and hence energy density ratings. 91 octane fuel is typically attained by simply adding octane enhancers as well as a cocktail of other detergents that vary from brand to brand and each one of those chemical compositions has varying levels of energy density so no two fuels will be EXACTLY the same energy density to begin with. So this idea "gasoline is gasoline" is hogwash you could sample Chevron 91 octane from two different gas stations and you'll find measurable variances in specific energy density and octane and thats measuring the SAME BRAND with the SAME RATING.

 

Some vehicles will get a little better mileage with higher octane because the computer can advance the timing more without predetination. That being said the purpose of wanting higher MPG is to save money. You will never make up the difference of high mileage with the cost of higher octane.

 

Dude... where are you? You are at Tacomaworld, where facts are just another man's opinion and technical data is hogwash.

Diesel fuel? Av gas? We are talking about fuel that goes into a Tacoma, nothing else.

Of course there are minute differences between a gallon of gasoline with "X" additives and a gallon of gasoline with "Y" additives. What, maybe a microjoule or something? Really?

C'mon man, for all intents and purposes, gasoline IS gasoline and, for any useful calculations, a gallon of gasoline contains around 120K BTU's, or 45Mj/kg. Rounding is your friend lol.

Now, where it DOES change, and a change that will actually affect the vehicle's efficiency, is the change from summer to winter gasoline. It can change up to 1.75% from these two blends. It has nothing to do with the gasoline and everything to do with excessive blending necessary.

If you really want to learn something, look at the "Gasoline Gallon Equivalent" tables here https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent.

In addition, depending on several factors, even labs will get different results using only pure "gasoline!" Pick a number, any number.


More sources
https://www.eia.gov/energyexplained/index.php?page=about_energy_units
https://hypertextbook.com/facts/2003/ArthurGolnik.shtml
https://www.engineeringtoolbox.com/energy-content-d_868.html

 

If only I could figure out how to utilize the gas from my 2 dogs...

 

Are you even listening to yourself? First you said I was wrong, then agree I was right but that it doesn't really matter LOL

Me "there is a 'negligible' but measurable difference in energy density of fuel"

you "NOPE! Fuel is fuel!"

me "here's evidence its not..."

you "yeah yeah but doesn't make a real world difference"

me "what do you think negligible means?"

I think you just like to argue so whatever dude you win

 

You're missing a couple things... these engines can vary the effective compression ratio with the VVT which can also allow the use of lower octane (and easier starting). Also, the Lexus, Camry, etc. have different air intakes that are tuned for higher rpm air flow while Tacomas are tuned for lower rpm air flow... a tune cannot make the Tacoma perform like the others... just ask OVTune.

 

I've talked with OVTune extensively actually, one of our larger issues is exhaust flow, not intake. Our cats and exhaust really choke flow at high power levels. While yes, the VVT can vary the compression ratio somewhat, the parts are the same on all the 2GR-FKS variants. Intake manifolds too. Here's the intake manifold , which is used on all Toyota 2GR-FKS engines. Toyota, as with 99% of all auto manufacturers is using the ignition timing to properly tune for fuel, because playing with the VVT to fiddle with compression is both complex, and will have other effects on the pumping of the engine in a way that ignition timing won't. It's a tune and exhaust issue, not an internal engine one.

 

And the intake runners, throttle bodies, air box, etc? (Answer: no.)

Edit: Don't want to make any more OT posts; so, I'll continue here... seeing as how the exhaust manifold is integrated into the cylinder head how different can the flow really be between all the 2GR-FKS vehicles? Is it being suggested that the Tacoma is the only one with restrictive exhaust?

 

2GR-FKS intake shenanigans (it's actually bipolar, just like the auto trans ):





Thread completely jacked. I have no idea if the Camry and/or IS 350 share this magic intake. Because I don't.. care?

 

The way gasoline is actually blended, and the varying percentages of the components used, will also have an effect.

Finally someone gets it.

A storage tank at a terminal can have gasoline refined from multiple different refineries, depending on the geographic area. So, TK-101 at X terminal can have 50mbbls of gasoline refined at an Exxon refinery, 100mbbls from a Shell refinery, and 75mbbls from a Valero refinery.

If this is a distribution terminal, when Jimbo's Gasoline Transport tanker truck pulls into the rack and fills the holds with gasoline, they're being filled with a nice cocktail of gasoline from who knows where.

A couple things to note.

93 octane gasoline is refined at the refinery using gasoline blender "recipies", calculated by the laboratory analytical data of various blendstocks that are produced from different units throughout the refining process. Same thing with 87, except refiners produce more 87 octane gasoline by volume because the demand for 87 is much greater and it's cheaper from a blending component volume and physical characteristic aspect. 93 uses more expensive / higher quality components, and that is a significant reason why it's more expensive at the pump.

How do you get the grades of gasoline that are in between 87 & 93? Usually the pump at your local gas station will pull a 1:1 (or whatever necessary) ratio from the underground tanks of 87 & 93.

Additives that are added to gasoline are held to strict quality control standards, if for no other reason than the liability to both the additive manufacturer and the "owner" of the gasoline. Same concept applies to refiners; refiners will actual target a slightly higher octane number than what is needed to account for any variances. For example, if the refiner is producing a batch of 87 octane gasoline, they may actually target octane number of 87.5. Having a batch of gasoline with an octane higher than needed is no problem, unless you account for economically "wasted" blendstocks that could have gone into blending 93 octane gasoline, but having a batch of gasoline with a lower octane number than what's needed is a huge - and expensive - problem. Can't sell what doesn't meet specification. Some additives are added at the refiner, or if a mistake has been made at a terminal, but those additives are mainly for corrosion control. The additive packages that we are actually wanting when we buy Shell or Exxon gasoline are added at the distribution terminal. Tanker truck pulls up to the rack, hooks up a hose for the gasoline to be transported, and another hose to dispense into the gasoline hold(s) the particular additives depending on where the gasoline is going to be delivered. Going to a Shell gas station? The additive package is going to be Shell's. Generally speaking, the gasoline doesn't matter because the variances between this station's gasoline and other station's gasoline of the same grade are lost in the wash.

Butane is a hell of a blendstock.

 

Very informative post!

 

Thank you!

I have almost 17 years of crude refining/finished fuels/specialty chemical experience, and have toyed with the idea of creating an all-encompassing post that covers refining and finished fuels, but I haven't gotten around to actually sitting down and writing it.

 

That process has always facinated me and truly there is not much information out there for the layman like me. Personally I don't come to this forum seeking answers much, as my career has uniquely prepared me to figure things out myself. That, plus building and modding for off road 30+ years ago let's me chime in occasionally with a solution to someone's problem. I try to stick with fundamental concepts tho.
Again, this is an informative post and I appreciate it!

 

The tanker that delivers fuel to Shell or Chevron drives straight to the generic stations and drops the same fuel in their tanks. The stations that sell the most fuel get resupplied with fresh fuel more often. It is the small mom and pop places that only get resupplied occasionally that have gas that goes bad.

Locally tankers only carry 87 and 91 octane. For 89 Octane they dump some of each and depending on how accurate they measure it the fuel you buy from an 89 octane pump could vary anywhere between 87 and 91. If they get an accurate 50/50 mix it will be 89.

 

Might be the same fuel but without the same, or any, proprietary additive package.

Cost of the additive package, or lack thereof, is an immense factor price per gallon you pay at the pump. When your low cost gasoline chain offers $0.20-0.30 off a gallon of gasoline versus the the station selling gasoline marketed by a supermajor, it isn't because the low cost seller is slashing their prices for the consideration of our wallets. Their gasoline may have an inferior additive package from some random specialty chemical company or worse, none at all.

 

Another example of corporate greed and consumer ripoff. If they could make $$$$ from 7 grades of gas, they would do it.
Go outside the US and will find ONLY one grade of gas. Cheaper to make, more consistent quality, fresher and in the end cheaper to consumers.

 

What? Care to elaborate on this?

 

89 can handle a higher compression ratio before detonating. Just because you put the fuel in, doesn't mean that you'll require the higher compression capabilities. If you were driving mild then your increased fuel efficiency probably came from driving habits.

I usually gas up with 87, but occasionally try the 91. I usually only average an extra 1-2 mpgs from the higher octane ratio stuff.