Premium fuel?

Sorry if it's been discussed to death before, but I did a forum search and no results...

So, I know the 4Runner doesn't need premium and I've ran nothing but the cheap 87 octane ethanol crap which is all we can get around here pretty much. Gas mileage has been 18.0 mpg for months.

Stopped at a gas station last week with only a couple of gallons left in the tank and decided to fill up with 93 octane, but still has ethanol.

There are a couple of stations that sell the ethanol-free premium, and I run that in my UTV and small engines. Good stuff.

With every other vehicle, putting premium in the tank resulted in a 1 or 2 mpg increase, so on a whim, decided to pay the big bucks and treat the 4Runner to a tank.

Over the past week, with half a tank left, mileage has gone down to 17.6 mpg. It feels noticeably more sluggish and I can see the difference in the real-time mpg display on the dash.

Weird.

I've never seen that happen in any of my vehicles over the years, from a 500hp GTO to a 2014 Ram Hemi, they all have gotten slightly better mileage and performance from the increased octane. Well, the Goat had 10:1 compression, so without premium, I had to retard the timing quite a bit to avoid pre-detonation, but...

So I fully understand the concepts of higher octane and how it effects engine function.

Just wondering if this is something unique to the engine management system of the 4Runner, or if I just got a bad batch of $4 gas?

 

There’s a reason why it called for 87 octane...

 

Sounds like you got a tank of E85. I wouldn’t go back to that station. They tried to pull that crap on me so I go all the way across town to fuel up.....

 

Sounds like you don’t fully understand the concepts of higher octane and how it effects engine function or you wouldn’t be asking this question.

 

No need to be that way, we could all be a little nicer this time of year, you know...

On every other vehicle I've owned, the computer would compensate for the higher octane by advancing timing and the result would be a slight increase in fuel mileage. The 4Runner got worse gas mileage, which I figured would be due to either the gas being bad or the 4Runner having a funky engine management system, which is why I posted the question here.

Sorry for wasting your precious time, geez.

 

BTW, I searched Google and found a thread on it on the "other" 4Runner forum and members reported increased mileage in their 5th gens, but not enough to compensate for the extra cost.

So I was correct in my assumption that it was probably just crappy fuel.

 

I notice a difference when fueling up at a “hot” gas station within five miles.....

 

Maybe it’s something similar to the placebo effect. You’re brain thinks the higher octane should give it better performance so your foot subconsciously makes it feel that way in seat of your pants by actually pushing it harder than you normally would. I know my Runner always runs better right after it’s been through the car wash. I attributed it to the lack of dirt causing less wind resistance (but I may be wrong).

 

One thing to consider. If you fuel up late in the day (especially if the station’s storage tanks are above ground), the fuel will have less energy per gallon because thermal expansion makes the fuel less dense (read the dispensing disclaimer fine print on the pump). Then, when the fuel in your tank cools off, there will actually be a smaller volume of fuel in the tank. There is about a 1% change in volume for every 19°F change in temperature.

http://datagenetics.com/blog/april32015/index.html

 

Sorry, but warmer, less dense air has less oxygen in it per volume, so less of the fuel gets burned thereby less power generated (pilots need to factor ambient air temperature in their aircraft performance calculations to make sure they have enough oomph to get off the ground with a given load, the cooler the air, the more hp can be created).

What you may be experiencing is cooler fuel in underground tanks expanding in your tank to actually give you more fuel to burn so the 20.0 gallons of cool fuel you bought expands to 20.2 or 20.3 gallons. More fuel = more miles.

 

Some vehicle ECU management software "learns" your driving style and fuel and also uses that to adjust your outcomes.
I know my 2010 Audi S5 had a specific "reset" (with vehicle off, turn key on, but not start, press pedal to the floor for x seconds, release pedal, turn key off for y seconds, then start car, or something like that) to tell the ECU to forget what it "learned" and start from scratch - quicker than running a few tanks of new fuel octane through it.

https://www.google.com/search?safe=...hUKEwiJrc2Pq5jmAhUDGTQIHZ1HC7AQ1QIoAHoECAsQAQ

Which is why after a fill up your "miles remaining" may change from previous fill ups.

 

Pretty sure its the other way around.

 

I mean less dense less MPG. Better in winter than summer.

Its already known vehicles perform better in colder air.

 

Sure

 

Same.

Not mine. Both my Tacoma and 4runner seem to prefer warmer weather.

Aside from that, it is a fact that cars get better fuel economy in the summer than the winter. I've observed it, and there are articles about it.

As far as the topic at hand; As @KSJ08. mentioned, I've also heard that it takes awhile for the ECU to adjust to higher octane fuel. I'm guessing that it's still not worth it in the long run.

 

But, it's true. Warm air is less dense and lowers wind resistance.

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

 

Tailgate closed is better.

I rarely get better than 17-18 MPG in winter. I regularly get 19-20 in the summer.

EDIT: my current tank is looking closer to 15.

 

A real brain teaser that will take lots of science and math to figure out...

I got 18.2-19.5mpg until I lifted the 4runner and put 285s on it... Now I get 16.5-17.2mpg...

Weird right? We ought to call up Bill Nye, Isaac Newton, Einstein, and the teenage mutant Ninja turtles to figure this out. I bet it has something to do with the equator and the way the toilet flushes... but I'll let the experts figure it out.

 

Warmer ambient air also means the engine warms up quicker so the air/fuel mixture gets leaned out sooner.

 

Not sure what your point is?

Are you adjusting for the fact that your tires are larger?

 

I have nine gas stations within eight miles of my house. Don’t get gas from any of them....

 

I was just being a smartass... The thread went from fuel octane, to ambient temperature, to tailgates... Thought I'd add in the mystery of larger, heavier, tires decreasing fuel economy too...

 

I should've figured

No good thread ever stay on topic

 

The underside of the truck is not very aerodynamic. The higher the ground clearance, the more air that can get tangled up in the hardware. Look at the average new Chevy or Ford 2wd pickup or any NASCAR car. They have air dams in front to redirect the air over or around the vehicle where the sheet metal is smoother in order to increase speed or efficiency.

Add to your lift those noisy mud terrain tires that you lifted your truck to install. The softer stickier tread compound takes more hp to push down the road (Olympic cyclists use very hard, very skinny tires, not big old fatty, high floatation knobbies).

Now, add the weight of all your cool off-road accessories (recovery gear, extra fuel cans and the brackets to mount them, rock sliders, the ‘roo guard bumper, winch, baja luggage rack) and you’ve significantly increased the mass of your truck. It takes more energy (fuel) to accelerate it from zero to 70, and even more fuel to overcome the now increased friction of those sweet tires.

The law of conservation of energy (energy cannot be created or destroyed, but can be converted to another form) states that the energy needed to produce the noise coming from your mudder tires has to come from somewhere. That “somewhere” is the oxidation of the fuel in your engine. Actually, a quieter tire (reviews are the best source of this characteristic) with a harder tread compound (the tread wear number is somewhat an indicator of this) will give you a little bit better MPG).

So, if you want to get better mileage, lower your truck, add a front air dam (so much for ground clearance), remove all the accessories (so much for the gnarly off-road warrior look), and run 150R75-17 street tires (so much for off-road traction).

 

was it raining? air is less dense when raining because the rain displaces the air. Aircraft have much less lift in the rain. Perhaps you were
not getting the correct air fuel mix?

 

I refilled it with premium from a different gas station and it already feels less sluggish and the mileage started going back up. So, just a crappy tank of gas, apparently.

 

So do you guys believe in winter gas?

I ran 93 in my Tacoma for a while. (91 isn't common around here) Didn't seem to improve gas mileage. Only noticeable difference was taking off on a hill with a 6spd and heavy 33's. It's like I had that 1 extra hp to get me moving lol.

My old Northstar Cadillac used premium. If I used regular 87, I'd lose a few HP and the car got worse mileage.

 

oooh aren't you a sassy pants

 

I read the manual on this just last night for my 2020 - It actually calls for a MINIMUM of 87 octane, it doesn't say don't go higher. It is the minimum, a huge difference.