Better gas mileage with different octane?

The 4Runner (with the same 4.0) owners manual recommended premium at least on the earlier years (mine was an 04) it did say regular could be run at a loss of hp and mpg. From what I heard that engine was originally built by Lexus to run on premium, but they adjusted the engine to run on regular with no issues, however if you did run premium supposedly you could pick up hp and mods. I always ran regular as I found the math didn’t work out in cost of premium vs 1mpg or so.

I’m assuming the new 3.5 wasn’t designed the same way as the old 4.0

 

https://www.usatoday.com/story/mone...gasoline-low-octane-too-much-ethanol/2369579/
While I'm sure you save a few cents running 85, there is no reason to do so, even in high altitudes. I just did a quick search and everyone from the .gov sites to SAE says the same thing. Modern engines will happily run at 87, even at altitude.
My key point: Let's say you run 85. Let's say something bad happens to your engine. Toyota does not give you a choice as the manual says 87. Do you want to give Toyota an out for a warranty claim? Sure, it probably won't happen, but why do it, especially if it does not give you anything except a few cents on the gallon?
https://en.wikipedia.org/wiki/Energy_density
https://mechanics.stackexchange.com/questions/6920/can-i-use-lower-octane-fuel-at-high-elevation
https://www.fueleconomy.gov/feg/octane.shtml

Bottom line: I don't think 85 will help or hurt anything in your Tacoma at high altitudes. I personally don't care what other people do. I only argued this point from a warranty objective. If people want power at high altitude, they should buy a turbocharged or supercharged truck.

 

This is kind of the point I’m making is it’s all in the software, I’m betting the version of this engine in the Lexus that is recommended to run 91 and makes more hp and torque is almost identical to the Tacoma with the exception of the intake and exhaust routing obviously. The software for the truck was designed to run it on 87 not anything else. There is no sensor in the fuel system that can measure octane rating of the fuel you are using. It has a knock sensor, so when you decide to go from 87 to 91, it begins to knock and the computer goes oh shit I better adjust my timing and injection duration and possibly idle speed so I don’t go boom. This does not usually mean you will make more power. But you are running the engine out of its happy peramiters and could affect other things.

 

Ok, onto the next topic, then.

 

No.

Please stop spreading misinformation.

 

So what does your Toyota owner's manual specify as far as octane rating? Pretty sure they did high altitude testing... I don't see 85 anywhere in my manual, except as a page number.

 

Did you know your manual also says:

* Obey the legal speed limit.
* Never install seat covers.
* Do not use control knobs while driving. Do you have manual hvac? Too cold? Too bad. Do not touch that dial until you've come to a complete stop.
* Do not read while driving---does that include the speedometer? They didn't specify.
* Do not talk on the phone while driving. Glad they made doing that so easy.
* Do not carry umbrellas.

Guess some people need a manual to tell them what to do.

 

Pretty sure the engineers at Toyota use science to figure this out not redneck math

 

Manual says 87 octane.

It also says my kettle boils water at 212°F, but that’s not what my thermometer reads (and it ain’t broke).

FFS, stop with the coy nonsense. If you don’t understand atmospheric pressure, please don’t speak about it.

 

If I go outside now and do a compression test on my cyls, it’ll be way out of spec from what the manual says too! Dang, my engine must be busted!! Help! Where are the Toyota engineers?

 

You realize static compression is very different from dynamic compression. Also your numbers will be bad because your engine is cold lol

 

This thread will be 6 pages by lunch

 

Well instead of debating how well you think your truck runs on 85 octane. Maybe you should read about effective compression ratio and how the computer uses variable valve timing to ensure proper cylinder pressures and combustion with the octane of fuel the computer software was designed to run.

 

I purchased my truck in November 2017. I babied my last and this is my first brand new truck so I am definitely going to baby it as well.

I have used premium 93 octanes at every fill-up and I've also added Stabil 360 performance to every tank. I just switched to Lucas Oil Products Ethanol Fuel Conditioner recently and used it in my last two fill-ups. My truck runs very smooth and I average almost 20mpg mostly highway at about 75-80mph. I've seen as much as 24mpg on longer trips. I have TRD intake and TRD exhaust and I like to zip around from time to time. I use synthetic oil as well.

I can tell you that even if the higher octane doesn't provide you better economy, it is better overall for the truck, especially with extended use. I have about 6k miles and still original oil and it still looks brand new and it's not brown or black at all. Of course, this has to do mostly it being so new, but the higher octane fuel and the fuel conditioner helps extend the life of the engine and makes it run smoother. Here in Houston we have Pure Gas available at certain stations which is ethanol free. I've also used that a few times. The conditioner helps to reduce corrosion in the tank, remove water/moisture from the fuel, and also remove ethanol from the fuel which prevents damage over time to the fuel system. Cleaner burner fuel, cleaner fuel system, and more efficient engine essentially leads to better fuel economy and better power delivery overall.

 

https://www.denverpost.com/2006/10/16/some-knock-states-lower-octane-levels/

https://www.fueleconomy.gov/feg/octane.shtml

https://www.usatoday.com/story/mone...gasoline-low-octane-too-much-ethanol/2369579/

https://www.autotrader.com/car-tech...hat-kind-of-gas-should-i-put-in-my-car-257810

http://rapidcityjournal.com/news/lo...cle_681e07bc-3cd3-5e0c-a3c7-c06fcc4d319c.html

 

Why do we even care about MPG? It's because we want more Miles Per Dollar. Yes, you might get higher mileage on higher octane because the vehicle's computer can adjust the ignition without detonation. It doesn't matter because economic benefit of more MPG can't be made up with the extra cost of higher octane fuel. You'll get way less Miles Per Dollar. You'll save much more money using the recommended octane level. If the vehicle is knocking/pinging using the recommended fuel, you have another problem that should be resolved.

 

Hey look at that real studies done showing using different octane than recommending is wasteful at best

 

My reply was more in to response of 85 octane being okay at high altitude.

In response to your assertion; it really depends on how the particular engine is optimized to utilize octane. To that end, there is not enough data on our particular engines to say one way or the other; especially considering it uses a quasi-atkinson cycle.

 

Also my numbers will be bad not because the engine is cold but instead because the atmospheric pressure of my engine's cylinder is only about 80% compared to sea level but I guess that's just redneck math again lol

Defining the difference between types of compression tests when we're talking barometric pressure differentials... nice Straw Man, bud.

Go back under your bridge.

 

You still fail to acknowledge that the ecu knows what altitude your at and has set parameters to run at that altitude that the software engineers already tested at when designing the truck