Octane. and how it effects your truck.

[wfo9]

Just thought i would share this.. take it for what it is worth. I've been digging into logs lately and surprised by how much knock most of these engines see in stock form on crap gas. They more or less learn their way around it by reducing timing and power, but if you tow or push it hard with a heavy load... I can't imagine not running premium whenever possible. You won't feel a big difference, but your motor sure will.

Your truck won't blow up on 87... but this is from someone who focuses on tuning Tundras for a living....and he gets a lot of questions about fuel.

Do I need to run Premium Fuel?

As we have reported with every truck we have tested on, 4.6L, 4.7L, 5.7L, all run best on 91+ octane weather they are completely stock with stock tune, or tuned. These engines pull 8-12 degrees of timing due to knock retard on 87 oct, 6-10 deg on 89oct, 2-6 deg on 91oct, and 0-2deg on 93oct. That is on a completely stock truck with factory tune.
If you care about the engine in your $35,000-$65,000 truck as you think you do, you wont run anything but premium in it weather you are tuned or not tuned.

EDITLEASE don't read too much into this post. I'm not saying your motor will blow up on 87 or won't last 100+ k running it. Just food for thought and an opinion from somone who tunes Toyota trucks. It's just one data point, but worth something IMHO.

 

[LandCruiser]

Most gas stations here only have 85 and 91, if you’re lucky some will blend up 87 for you.

 

[5280 TRail-Runner]

Just thought i would share this.. take it for what it is worth. I've been digging into logs lately and surprised by how much knock most of these engines see in stock form on crap gas. They more or less learn their way around it by reducing timing and power, but if you tow or push it hard with a heavy load... I can't imagine not running premium whenever possible. You won't feel a big difference, but your motor sure will.

Your truck won't blow up on 87... but this is from someone who focuses on tuning Tundras for a living....and he gets a lot of questions about fuel.

I'm sitting on around 14k miles and have run nothing but 91 from Shell with the exception of 1 tank and that was because there was no local shell around and did not want to risk running out before getting to one. Most will say its a waste of money but the money you spend on the car itself, you might as well take care of the motor.

 

[Trixx]

When I did my 8000 mile trip a couple months ago I logged fuel mileage on every tank. While up north, I found I got noticeably worse mileage on tanks with 87 and ethanol. Those primarily located in the northern midwest. The 87 down south was definitely superior.

That aside, I feel that if octane made a noticeable difference in terms of reliability, it would’ve been specified to use by Toyota. While I have no doubt it performs better with premium, I don’t think there would be any kind of noticeable difference in long term reliability to the masses.

Sounds similar to the argument about changing the oil every 5k vs the 10k specified in the manual.

 

[perf0rmance]

Short reply: stick to factory recommendations.

Factory recommendation: 87-octane.
Source: https://pressroom.toyota.com/releases/2016+toyota+4runner+product+specs.download



Long reply: follow whatever the engine is spec’d for.
Quick lesson - octane rating is essentially the how resistant the gasoline is to ignition. The higher the Octane, the higher the pressure/heated can be sustained before the gas will self-ignite. This is especially important to turbocharged and supercharged engines. High-boost applications often use race gas (110+ octane).

Running higher octane than what your engine is tuned for can net you less HP produced... so yes, there is negative performance aspect to running incorrect gas. Running LOWER octane than what’s recommended is much worse, of course, as your engine can “ping” or suffer from detonation.


Here’s an interesting thread from here:
http://www.toyota-4runner.org/maintenance-detailing/683-premium-vs-regular-fuel.html

 

[EEEliminator]

When I did my 8000 mile trip a couple months ago I logged fuel mileage on every tank. While up north, I found I got noticeably worse mileage on tanks with 87 and ethanol. Those primarily located in the northern midwest. The 87 down south was definitely superior.

That aside, I feel that if octane made a noticeable difference in terms of reliability, it would’ve been specified to use by Toyota. While I have no doubt it performs better with premium, I don’t think there would be any kind of noticeable difference in long term reliability to the masses.

Sounds similar to the argument about changing the oil every 5k vs the 10k specified in the manual.

Ethanol makes sense...

Octane shouldn't make any difference if you don't need it higher octane to ward off detonation. If you want to pay more for premium because you like it than more power to you. On a stock N/A motor your not going to see any difference, you're not in a controlled environment.

 

[MossJenks]

Most gas stations here only have 85 and 91, if you’re lucky some will blend up 87 for you.

That's because we live a mile high! Thinner air = harder to burn the fuel. 85 in Colorado is at LEAST as ping-proof as 87 at sea level.

You might get a little more power if the computer is programmed to advance the spark enough in response to the knock sensor, but putting higher octane gas is not going to make the engine last longer in any way.

 

[1engineer]

I'm waiting to hear what negative effects happen when timing is adjusted for 87. I know for a fact that durability and reliability are much higher when you are not pushing higher power.

 

[TEujunga]

I find it pretty implausible that Toyota engineers would configure an engine to run so poorly on 87-octane gas that the ECU must consistently pull 8-12 degrees of timing in order to avoid detonation -- and then go ahead and specify 87-octane as the recommended fuel.

The competition for automotive powertrain engineers to squeeze the last erg of efficiency out of their products is insane these days. Every possible parameter is exhaustively considered and tested in configuring an engine to run best at a particular octane rating. If they configured the engine to run that much better or last that much longer on higher-octane gas, then that is what they would recommend for use (and often do, on premium models with higher static compression or forced induction).

 

[GearJunkie88]

I ran the "crappy" low octane gas in my 2008 4Runner for 100,000 miles before I got my 2017. My dad now has my 2008 and still uses the low octane stuff. If that gas is bad for the engine, it sure doesn't seem to damage it too badly for 100,000+ miles. Granted, I live in TX where we make the gas. Perhaps we keep the "clean" low octane stuff for ourselves and send the "lousy" low octane stuff up north.

 

[Jeremy556]

I find it pretty implausible that Toyota engineers would configure an engine to run so poorly on 87-octane gas that the ECU must consistently pull 8-12 degrees of timing in order to avoid detonation -- and then go ahead and specify 87-octane as the recommended fuel.

The competition for automotive powertrain engineers to squeeze the last erg of efficiency out of their products is insane these days. Every possible parameter is exhaustively considered and tested in configuring an engine to run best at a particular octane rating. If they configured the engine to run that much better or last that much longer on higher-octane gas, then that is what they would recommend for use (and often do, on premium models with higher static compression or forced induction).

The 1GRFE is designed for high octane fuel. Without the ability to adjust timing based on knock sensor, high octane fuel would be a requirement for the engine. Even in the old single VVTI version this was the case.

I forget if it was the first year of the FJC or the 2010 year with the new dual VVTI, they listed 91 octane as a requirement. Many negative magazine reviews citing the premium gas cost penalty caused the specs from Toyota to instantly change to 87.

You can see the timing advance with as simple a logging setup as a bluetooth OBD2 reader and Torque on your phone.

To the question of does running 87 in the stock 1GRFE cause any damage or negatives, other than reduced power? I do not believe so, as I have not seen any evidence to support that claim.

 

[wfo9]

It's one of those things where if you never see it.. or hear it.. you don't think about it. But when you actually start analyzing the data it is a bit shocking to see how much these engines see knock.. Then when you see how much of a difference good gas makes (people who tune them for a living...) They tend to feel strongly about it.

I'm not saying they won't run on 97 for a long time without any issue.. Just surprising how much knock is built into the factory tune on 87 (at near sea level.. totally different up at altitude). It really does struggle on low octane under heavy loads... even in stock form. You have to understand how the decay strategies work to have an opinion. I don't completely get it yet, but someone who does.. has a strong opinion about it. So I posted it up as food for thought.

There should be nothing to worry about.. but I see a lot of 5th gen guys over maintain their trucks.. but feel cheap gas is the way to go. Not saying it is wrong, just something to think about.

 

[RonJR]

Pretty much every automotive engine made since the late 70's has had a knock sensor. That device is in there for one purpose, to optimize ignition timing for whatever fuel you put into it, as well as altitude, temperature, manifold pressure, rpm, etc. The ECU has a base timing map for all of those parameters, and then it runs a feedback loop where it continually advances timing from the base level until it detects lo-level pinging, and then backs the timing off until the pinging stops. Then it slowly advances timing again, repeating the continuous hunt for the optimum timing for conditions. It's basically the same thing as having a super tech riding along with you continuously listening to the engine and tweaking timing for optimum performance without pinging.

So, if all is working correctly, you won't hurt the engine by running low octane fuel - the ECU will just retard timing to prevent pinging. Horsepower and fuel economy will suffer, but since the lower octane fuel is cheaper, that's a tradeoff many people are willing to make. Conversely, higher octane fuel will allow the ECU to advance timing for better performance and/or economy. Toyota recommends 87 octane because that allows the engine to meet its specified horsepower and fuel economy ratings. They could have spec'd 85 for lower/cheaper performance, or 89 or 91 for better performance, but chose 87 because the 4runner is marketed as a vehicle for the "common man", not a performance vehicle.

I'll make a related comment here. When you get a knock sensor malfunction code, it does not mean that the engine is pinging. It means that the ECU is not getting a useful signal from the knock sensor. In that case the ECU is "flying blind" with respect to ignition timing, so to protect the engine it assumes the worst and greatly retards timing making your engine run poorly, with little power.

 

[wfo9]

Pretty much every automotive engine made since the late 70's has had a knock sensor. That device is in there for one purpose, to optimize ignition timing for whatever fuel you put into it, as well as altitude, temperature, manifold pressure, rpm, etc. The ECU has a base timing map for all of those parameters, and then it runs a feedback loop where it continually advances timing from the base level until it detects lo-level pinging, and then backs the timing off until the pinging stops. Then it slowly advances timing again, repeating the continuous hunt for the optimum timing for conditions. It's basically the same thing as having a super tech riding along with you continuously listening to the engine and tweaking timing for optimum performance without pinging.

So, if all is working correctly, you won't hurt the engine by running low octane fuel - the ECU will just retard timing to prevent pinging. Horsepower and fuel economy will suffer, but since the lower octane fuel is cheaper, that's a tradeoff many people are willing to make. Conversely, higher octane fuel will allow the ECU to advance timing for better performance and/or economy. Toyota recommends 87 octane because that allows the engine to meet its specified horsepower and fuel economy ratings. They could have spec'd 85 for lower/cheaper performance, or 89 or 91 for better performance, but chose 87 because the 4runner is marketed as a vehicle for the "common man", not a performance vehicle.

I'll make a related comment here. When you get a knock sensor malfunction code, it does not mean that the engine is pinging. It means that the ECU is not getting a useful signal from the knock sensor. In that case the ECU is "flying blind" with respect to ignition timing, so to protect the engine it assumes the worst and greatly retards timing making your engine run poorly, with little power.

Since the late 70s LOL.That is funny. Think you got your decades way off. Ford put the first knock sensors in the mustang GT in 05.. It's been pretty common on most platforms since the late 90s but the processing was never fast enough to work at high RPM. The sensors are just microphones more or less. The tough part is analyzing the signal and filtering out noise. They all pretty much pick up false knock from various things at times.

It's still very much guesswork. It's not ideal for it to be constantly getting knock and adjusting to avoid it. The rated HP for the 1grFE is done on 93. I can't remember the 87 numbers, but I have seen them published before. I'm sure someone remembers what it is for sure. I think it was 258 hp and 270tq.

 

[LandCruiser]

Since the late 70s LOL.That is funny. Think you got your decades way off. Ford put the first knock sensors in the mustang GT in 05.. It's been pretty common on most platforms since the late 90s but the processing was never fast enough to work at high RPM. The sensors are just microphones more or less. The tough part is analyzing the signal and filtering out noise. They all pretty much pick up false knock from various things at times.

It's still very much guesswork. It's not ideal for it to be constantly getting knock and adjusting to avoid it. The rated HP for the 1grFE is done on 93. I can't remember the 87 numbers, but I have seen them published before. I'm sure someone remembers what it is for sure. I think it was 258 hp and 270tq.

I wonder how bad the 85 octane numbers are at 7500 ft?

 

[Jetboy]

I think that the question here is weather higher octane fuel means less knock or ping occurring in the engine. I think that is unlikely to be the case. The system should advance timing until the knock sensor tells it to back off and then back it off slightly. It likely continues to do this cycle repeatedly over and over constantly testing the limit of timing advance. The result is that whether you're burning 91 octane fuel or 87 octane fuel you get the same advance in the cycle. The difference is the knock happens at a different timing advance number with 87 or 91 fuel. The knock happens the same amount in both just at different levels of timing. For this reason I don't think that higher or lower octane fuel would make any meaningful difference in the longevity of the motor. It is fairly easy to make the case that higher octane fuel should have the ability to run more advanced timing and produce more power.

 

[TEujunga]

The 1GRFE is designed for high octane fuel. Without the ability to adjust timing based on knock sensor, high octane fuel would be a requirement for the engine. Even in the old single VVTI version this was the case.

I forget if it was the first year of the FJC or the 2010 year with the new dual VVTI, they listed 91 octane as a requirement. Many negative magazine reviews citing the premium gas cost penalty caused the specs from Toyota to instantly change to 87.

You can see the timing advance with as simple a logging setup as a bluetooth OBD2 reader and Torque on your phone.

To the question of does running 87 in the stock 1GRFE cause any damage or negatives, other than reduced power? I do not believe so, as I have not seen any evidence to support that claim.

Ah. I see I was mistaken. Pardon my ignorance, and thanks for setting me straight.

It's still not quite adding up for me, though. I still find it hard to imagine that every aspect of the engine -- static compression, valve timing, swirl/tumble, flame propagation, combustion temperature regulation via EGR, etc., etc. -- was originally optimized for premium fuel, and the only things making it an 87-octane engine are a set of knock sensors and a sentence in the owner's manual.

Will be interested to learn more.

 

[wfo9]

I think that the question here is weather higher octane fuel means less knock or ping occurring in the engine. I think that is unlikely to be the case. The system should advance timing until the knock sensor tells it to back off and then back it off slightly. It likely continues to do this cycle repeatedly over and over constantly testing the limit of timing advance. The result is that whether you're burning 91 octane fuel or 87 octane fuel you get the same advance in the cycle. The difference is the knock happens at a different timing advance number with 87 or 91 fuel. The knock happens the same amount in both just at different levels of timing. For this reason I don't think that higher or lower octane fuel would make any meaningful difference in the longevity of the motor. It is fairly easy to make the case that higher octane fuel should have the ability to run more advanced timing and produce more power.

Not the way it works (at least in my opinion and experience). Read the first post explaining what he sees on all the Tundras. I can't say how this ECU works for sure, but based on others and what I have seen it goes something like this

There is a base timing map for a a given load cell (picture a table of RPM on one axis and load value from 0-100 on the other). There are further adder adjustments on this based on IAT, Coolant Temp... You start the car for the first time ever with 93 in it.. It will run the timing from the base map (except at idle and decel which are different animals). If it sees knock frequencies it will use that instant feedback to drop timing a little (and decay it), but will also log that knock instance into a learn factor for that cell. Next time around in the same cell it will use the learn value to adjust the base. If there is no feedback knock it will decay the learn a little for the next time... How this decay works exactly and how fast it is... is very much in question, but I have observed the general concept take place pretty rapidly in the logs. This is why 87 knocks a lot and why 93 rarely does. Once the 87 has been in there a while. it learns it, but it keeps trying to get back to the original map at some unknown rate.

It will not keep adding timing once all the base map timings are hit with no negative feedback. You can't just keep adding timing as that would be counter productive (plus this can be observed in the logs pretty easy). The main issue you have with learn for low octane fuel is that you simply won't get into all the cells very often.. So when you do.. it bangs around. the engine can take it.. but it is just not ideal thus the benefit of running good gas .

Now if you never tow or work the motor much at all (just putt down to whole foods to pickup some quinoa..) Then I can't imagine it making any difference at all. If you climb big hills, tow or just generally beat on it... good gas is worth it IMHO.

 

[Jetboy]

It seems like we could just collect the data on the knock sensor and find out. I don't think that the timing retard necessarily has any meaningful correlation with the number or frequency of knock sensor readings. The other easy way to test this would be to compare the timing advance with an even higher octane fuel. If 100 octane fuel adances a timing beyond a 91 octane fuel then it would be pretty obvious that the amount of knock over time is going to be the exact same or very close with any pump fuel. The only scenario that I can envision where there would be any difference would be one where the base map or the goal timing does not result in any ping or knock. If it's actually the case that 91 octane fuel does not reach that threshold then there would be a difference. A bottle of octane booster would provide the answer.

My guess is that the knock sensor is very early to identify a frequency in the engine block. Enough so that it reduces timing advance long before there is any engine wear.

 

[ubertoyotax]

So at altitude (5400+), would it better to run 87 or 91?