So what exactly happens if you run Premium in a 4Runner?

[Something_Awesome]

I decided to go back to the manual. I actually went back and looked at the manuals for all naturally aspirated vehicles I have owned. None of them actually state, explicitly, that 87 is recommended. All the manuals state to use 87 or higher.

This can mean a couple things:

(1) Use 87, but if 87 is unavailable at your station, then there is no problem using 89 or 91; or, (2) While 91 will be best, your vehicle still accepts 87.

The thing is, when it comes to disclosures and things of this sort, and they become sort of boiler-plate or standardized, companies won't change them. It makes zero sense to, even if there is useful information (like 91 may increase performance/MPG/longevity) being withheld from the end user. I'm going to take the fuel in my tank down to a point where I have like 3 miles left before empty, and fill it with 91. I want as little "taint" as possible in my tank filled with 91 lol. Can't wait to try this. Too bad I don't drive the 4Runner much. Could be a week or 2.

What's more is that all the 91 users claim better MPG. Like in the 19-21 range. That makes no sense. The standard Toyota uses to measure MPG means, in theory, you should not average anything above 18.999999 MPG (unless you're violating traffic laws).

 

[Whippersnapper02]

Some states do bot use ethanol in their 91 or higher grades. That would increase mileage.

 

[AMLOR]

Myth busting....

I use premium exclusively, 91 pure gas. I believe the Dual VVT does adjust the timing. To protect the engine it takes about 1000 miles of consistent premium gas for the ECM to make the full adjustment. If you use one tank of of 87 octane the ECM adjusts back (retards) the timing immediately and you'd need another 1000 miles of premium to regain the ecm timing adjustment. Im not sure this is 100% accurate but it is what I've pieced together. My truck is fast! I'm getting 18.9 MPGs all summer.

PLEASE do not confuse the DUAL VVTI system timing (it increases VALVE duration above 3500ish rpm); with IGNITION timing, which is controlled by the ECM. The two systems have (almost) NOTHING to do with each other.

The Toyota 4runner DOES NOT have a "gasoline quality sensor" for lack of a better term. SOME cars (Mercedes, Porsche, Ferrari etc.) DO have this sensor...but NOT a 4runner. The ECM does not know what you just loaded in the tank.

The ECM works on an if/then flowchart sort of decision making process.
IT IS NOT CAPABLE OF "LEARNING" in the classic sense of the word.
IT is ONLY a series of "MAPS" and sensor data that enable it to control the engine.
The ECM uses sensors like throttle position sensor, O2 sensors, knock sensors, engine temperature sensors, Intake air temperature sensors, etc.
to guide the if/then decision making process.

Simple example: for S&G lets assume that your truck is pulling a 2500pound trailer at highway speeds, and you filled up with 83 octane 10% ethanol fuel.
We will also assume that you are driving between Dallas and Houston 75MPH
and it is mid August with an outside temp of 98 degrees.

What is the ECU doing in this scenario?

Well it depends on the sensor data...lets say that on a cool spring day with the same load and speed the ecu allows the truck 30 degrees of IGNITION timing...but today it is so hot that your crappy gas begins to knock, and the knock sensor now only allows 20 degrees if IG timing.
IF, AND ONLY IF you had bought 93 octane gas, you MIGHT not have had your engine knock and you would happily be cruising down the road at 75+ mph, swearing that 93 octane makes more power, instead of wondering why your 4runner "just isnt running very well today."

The 4Runner ECM is ALWAYS looking to give the engine MAXIMUM timing all the time. BUT, those pesky sensors, hot summer (and very cold winter) days, crappy fuel, driving style, clogged air filters ETC, ETC, ETC...
get in the way of all the timing, all of the time.


Takeaways:
The Dual VVTI system is RPM dependent and a mechanical system for high RPM power. Period. It is essentially independent of the ECM.
The ECM is NOT SMART. It MUST rely on sensor data to control the engine.
The ECM has NO WAY TO KNOW what fuel you are running.
The ECM does have a short term memory that is continually being overwritten by new data from the sensors. It MAY save that data (for a period of time) IF it detects a pattern. Perhaps used to access the last program MAP that was used.

As much as we love our 4runners, there is a tendency to praise our trucks for things it is not capable of; and blame our trucks for things it was programed to do, whether we like it or not...
AMLOR

 

[cobbrg]

Just throwing in my anecdotal experience to this thread.

I tow a 2000lb trailer with a 2017 4Runner that is at max payload. Having crossed the country several times with this setup, it is my experience that higher octane and less Ethanol make a significant difference. I will get as low as 8.5 MPG with 87 octane w/Ethanol and as high as 12 MPG with 93 octane. This is traveling the same terrain. Headwind/tailwind makes a difference too.

The power difference is probably least subjective when using cruise control. The truck downshifts so much with low octane fuels that cruise control is unusable even on relatively flat ground. When running the lower octane, I will settle for 5-15mph slower climbing large hills than with the higher octane (because I am monitoring transmission temps).

I've tried this experiment back and forth many times. Putting in higher octane is expensive, but we get better range and a safer trip.

EDIT: I mention octane, but it is quite possible that it is the Ethanol content making the difference. On a recent trip to upstate New York, a fill-up of no-name 93 octane w/Ethanol was awful and a 91 octane w/out Ethanol was the best power of the trip.

 

[AMLOR]

Just throwing in my anecdotal experience to this thread.

I tow a 2000lb trailer with a 2017 4Runner that is at max payload. Having crossed the country several times with this setup, it is my experience that higher octane and less Ethanol make a significant difference. I will get as low as 8.5 MPG with 87 octane w/Ethanol and as high as 12 MPG with 93 octane. This is traveling the same terrain. Headwind/tailwind makes a difference too.

The power difference is probably least subjective when using cruise control. The truck downshifts so much with low octane fuels that cruise control is unusable even on relatively flat ground. When running the lower octane, I will settle for 5-15mph slower climbing large hills than with the higher octane (because I am monitoring transmission temps).

I've tried this experiment back and forth many times. Putting in higher octane is expensive, but we get better range and a safer trip.

EDIT: I mention octane, but it is quite possible that it is the Ethanol content making the difference. On a recent trip to upstate New York, a fill-up of no-name 93 octane w/Ethanol was awful and a 91 octane w/out Ethanol was the best power of the trip.

Your observations are completely valid. Ethanol is NOT your friend, regardless of the octane you select. The issue is that ethanol has only 2/3 the energy density of gasoline per gallon.
As you might guess, on a 20 gallon tank of 10% ethanol "gas"; you have 2 gallons of liquid (ethanol) by volume. Those "2 gallons" DO affect your engine power potential negatively.

While I have 4.88 gears, I ALWAYS tow with the highest octane fuel I can find and will pay for "real gasoline" when I can find it.
For reference, I tow a 4800lb Airstream with the 4runner. I tow in 4th gear at about 60-65mph, about 3200 rpm, and get 10.5 to 11.0 MPG doing it.
AMLOR