OCTANE: Why 91 and not 87? (1 Viewer)

[SROak]

Can someone explain why we need to put 91 gasoline in the GX550 while the Toyota Tundra only requires 87? These both have the V6 twin-turbo engine, right?
If this is simply because the GX550 is tuned for 91, is there a replacement chip that can tune the engine to run 87 gasoline?

The price difference here in California can be significant.

 

[Jesse H]

Because Lexus. Interestingly enough, the Toyota actually makes more power than the Lexus but uses lower octane.

There are some differences between the two as the GX does have smaller turbos which would create and deliver power differently. There are tunes out there for 87. I haven't gotten around to it yet, since it's my wife's truck, but I'm planning on the 93 tune which should yield a noticeable difference in power.

 

[SROak]

There are tunes out there for 87.

Do you have any links for the 87 octane tune for GX550?

 

[munkeeboi]

Do you have any links for the 87 octane tune for GX550?

Here you go.

No major power gains with the 87 tune...just allows reliability with 87 pump gas

You can follow this thread for more info. go to post #120 for tune differences

VF Tuner ECU/TCU Tuning for the GX550

Hey Everyone! VF Tuner here and we want to let you guys know we have support for the GX550! That includes tuned packages as well. This is a real calibration for the ECU and TCU. (engine and transmission). This engine is capable of 100+ ft lbs of torque gain and 50+ horsepower just with a few...

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VF Tuner Wiflash GX550 2024+ Tune Package

comes with VF Tuner Wiflash kit (with license and credits for 1 vehicle) Access for ECU reading / writing of Toyota Gen4 ECUS (2024 GX550) CAN Patch harness (for connection / flashing)OTS Tuned maps options: - 87 octane OTS Map - 87 octane OTS Map with v1 transmission tune - 91 octane OTS Map -...

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[jordanfsl]

I mean, you can also just put in 87 and no harm will be done. The ECU will compensate, although it might actually lower fuel economy and/or power. Any modern car will do this.

 

[jpto]

I mean, you can also just put in 87 and no harm will be done. The ECU will compensate, although it might actually lower fuel economy and/or power. Any modern car will do this.

It's a personal decision if you want to put in 87 vs 91. You're absolutely right that any car will compensate.

I put in 91 or higher because the timing changes a ECU makes is reactive, it has to detect something is off and then changes timing. I know this happens in a fraction of a second but I feel better that there's a bigger window of safety using a higher octane since gas quality can vary a lot and don't want to put in a low quality batch of 87.

 

[Baba Ghanoush]

Can someone explain why we need to put 91 gasoline in the GX550 while the Toyota Tundra only requires 87? These both have the V6 twin-turbo engine, right?
If this is simply because the GX550 is tuned for 91, is there a replacement chip that can tune the engine to run 87 gasoline?

The price difference here in California can be significant.

Just to discuss the price difference here in California. Assuming you average 12,000 miles driven in a year and you average 15 miles per gallon, you're looking at approximately 800 gallons of gas a year. With the current price differential of roughly $.40 between regular and premium, that equates to an extra $320 extra spend in a year's time. I'm not trying to make an argument either for or against 87 vs 91, but on a vehicle at this price, I would think an extra $320 a year on gas shouldn't be an issue. If it is, it's time to rethink the vehicle purchase and spending habits.

 

[KAR120C]

I mean, you can also just put in 87 and no harm will be done. The ECU will compensate, although it might actually lower fuel economy and/or power. Any modern car will do this.

A modern car's ECU has fuel and timing maps that will attempt to protect the engine in the case of low Octane fuel. I would stop short of saying no harm will be done. If the car is designed to run on 91+ it will retard timing as it detects knock but the idea is that 91 will not produce major knock and usually a single adjustment will stop knock on the next firing cycle of that cylinder.

87 MAY require multiple knock detection cycles before it retards the engine enough. That means you may actually be able to actually hear some pinging from the engine. If this happens occasionally because you accidentally put in some low octane gas, most likely it will not damage anything. But if you are doing it as a regular thing, then all the pinging and high retardation of timing is not going to be good for your engine. No, you may not blow a hole in your piston, but it can certainly be harmful.

Usually a manufacturer will say in the manual if they will allow lower than recommended octane and will adjust to lower performance. However, if they tell you straight out not to go below 91, and you just spent $80k on a new car, its beyond me why you would take that risk.

 

[JoeRob]

Over the long term, running a lower than recommended octane may get your engine warranty voided - if a history of 87 octane is established by Lexus/dealer.
Over the nearer term, running 87 octane may cause the engine timing to retard to the point you will noticeably get poorer performance from the engine and your foot may end up deeper into the accelerator and causing higher use of fuel in the end trying to get better response.
If you tow while burning 887 octane????
Just run 91 octane and forget about it.
Don't use the ECO settings on the GX - it screws up the A/C and who knows what else and if you want A/C performance?????
But if you do burn 87 Octane, let us know how it goes.

 

[jclaffee]

Just to discuss the price difference here in California. Assuming you average 12,000 miles driven in a year and you average 15 miles per gallon, you're looking at approximately 800 gallons of gas a year. With the current price differential of roughly $.40 between regular and premium, that equates to an extra $320 extra spend in a year's time. I'm not trying to make an argument either for or against 87 vs 91, but on a vehicle at this price, I would think an extra $320 a year on gas shouldn't be an issue. If it is, it's time to rethink the vehicle purchase and spending habits.

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