Fuel discussions/questions - Octane Regular or Premium (merged threads)
06-22-23, 11:12 AM
#496
We live on the coast in Florida so pretty much every gas station has ethanol free pretty cheap. I think I paid 3.45 last week for 93 ethanol free. If we don't use ethanol free in our boats down here it will destroy the fuel lines and anything else rubber...turns them into gum. Another benefit of ethanol free is it doesn't break down like regular fuel, guess that only benefits those whose car sits a lot.
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John00 (06-22-23)
06-22-23, 11:32 AM
#497
Pole Position
We live on the coast in Florida so pretty much every gas station has ethanol free pretty cheap. I think I paid 3.45 last week for 93 ethanol free. If we don't use ethanol free in our boats down here it will destroy the fuel lines and anything else rubber...turns them into gum. Another benefit of ethanol free is it doesn't break down like regular fuel, guess that only benefits those whose car sits a lot.
Last edited by ASE; 06-22-23 at 12:05 PM.
06-22-23, 12:39 PM
#498
Intermediate
The bottom line (not my opinion):
Regular can be used at least occasionally without repercussions in most vehicles designed for premium, but it’s a bad idea to make a habit of it. Bottom line: Check the owner’s manual. If the vehicle manufacturer says the engine requires premium, believe it. Don’t try to save a few cents per gallon by buying regular gasoline. Doing so could lead to much larger expenses in the future.
The Bottom Line
The computers that manage modern engines are able to adjust the ignition system to accommodate lower-octane gasoline — to a point. With regular gas, fuel economy and acceleration will likely deteriorate at least slightly. Because regular has lower octane, it is more prone to detonation. Burning regular in an engine designed for premium on a long-term basis or under heavy loads can cause engine knock, and that in turn can damage the pistons, valves or spark plugs. Due to the presence of knock sensors and the car’s ability to retard the spark timing, you might not hear knocking, but that doesn’t mean premium is unnecessary.Regular can be used at least occasionally without repercussions in most vehicles designed for premium, but it’s a bad idea to make a habit of it. Bottom line: Check the owner’s manual. If the vehicle manufacturer says the engine requires premium, believe it. Don’t try to save a few cents per gallon by buying regular gasoline. Doing so could lead to much larger expenses in the future.
06-22-23, 03:35 PM
#499
Intermediate
The issue with these discussions is some seem to believe a Toyota 4.6 is something special, it's not. It a very commodity product with many applications. I'd like to see just one example of 87 destroying an engine or at a minimum causing repairs.
A Ferrari these are not.
Used 87 in a 2015 GS350 for 120k miles, not a single CEL ever.
A Ferrari these are not.
Used 87 in a 2015 GS350 for 120k miles, not a single CEL ever.
I would be surprised if Lexus just put down the premium gas requirement as a joke of some sort.
There are many ways to save $$$ on a car, not replacing the air and oil filters will save you money, removing the cabin filter will also be fine, no negative effects, 20k oil changes will probably be fine too. Brake, AT, TC and diff fluids for life, no need to waste your money.
Last edited by NewB2Lexus; 06-22-23 at 03:45 PM.
06-22-23, 03:52 PM
#500
Pole Position
I don't want to beat the dead horse here and I simply do not have enough insight of how Toyota embeds its engines in different models. Just because the block and the top end is the same it does not mean it runs with the same parameters (compression, ignition, cam timing etc. which are mostly controlled by the ECU). If you know for a fact that the GX460 runs with the exact same parameters as the Sequoia than using the same octane is probably ok.
I would be surprised if Lexus just put down the premium gas requirement as a joke of some sort.
There are many ways to save $$$ on a car, not replacing the air and oil filters will save you money, removing the cabin filter will also be fine, no negative effects, 20k oil changes will probably be fine too. Brake, AT, TC and diff fluids for life, no need to waste your money.
I would be surprised if Lexus just put down the premium gas requirement as a joke of some sort.
There are many ways to save $$$ on a car, not replacing the air and oil filters will save you money, removing the cabin filter will also be fine, no negative effects, 20k oil changes will probably be fine too. Brake, AT, TC and diff fluids for life, no need to waste your money.
06-22-23, 04:35 PM
#501
knock sense works. chemicals do react. the warranty isnt based on the reaction, the design life is used to determine if the component gets used. The FA lab checks with interval inspection for fractures. these are at accelerated times due to reaction which is increased with heat. Arrhenius equation is used to model the polymer accumulated damage. one test puts the polymer into a cylinder of ethanol, heats and agitates, then swaps in new ethanol to restart reactions.
The bottom line is that you dont know what octane fuel you are using. the minimum is stated, but thats not what you really get.. you get whatever the profit-loss curve says is optimal to ship. absolute safest is ethanol free.
as stated before, the requirement is to meet declarations. the regulatory checks sample vehicles and check. those checks are required to use whats stated and in original stock config. tires are a huge part.
The bottom line is that you dont know what octane fuel you are using. the minimum is stated, but thats not what you really get.. you get whatever the profit-loss curve says is optimal to ship. absolute safest is ethanol free.
as stated before, the requirement is to meet declarations. the regulatory checks sample vehicles and check. those checks are required to use whats stated and in original stock config. tires are a huge part.
06-22-23, 04:38 PM
#502
Pole Position
Sorry but ... Huh-What ?
Last edited by ASE; 06-22-23 at 04:42 PM.
06-22-23, 04:49 PM
#503
response to someone without enough knowledge to understand how ethanol and materials reactions are tested. A failure analysis lab puts the parts into a glass container that heats and agitates. after a while the part is removed, inspected, then new chemical added and started over.
06-22-23, 04:54 PM
#504
https://www.nrel.gov/docs/fy06osti/38834.pdf heat and agitation are used to accelerate the test to get results faster. the data is used to determine activation energies, arrhenius equation is what is used in the determination. then they are compared relativistically to other materials. sometimes they are then given an industry standard classification but they still get tested anyways.
06-22-23, 05:16 PM
#505
Intermediate
response to someone without enough knowledge to understand how ethanol and materials reactions are tested. A failure analysis lab puts the parts into a glass container that heats and agitates. after a while the part is removed, inspected, then new chemical added and started over.
No mention of ethanol.
The link you posted takes you to a document titled: "Elastomer Compatibility Testing of Renewable Diesel Fuels". Not sure how's that even relevant unless you own a diesel GX.
I am undoubtedly no expert in chemistry but so far I failed to see how using higher octane gas instead of regular will accelerate wear on polymers or such polymers are even used by Toyota for components built into the GX (as you stated earlier).
Last edited by NewB2Lexus; 06-22-23 at 05:25 PM.
06-22-23, 07:30 PM
#506
Without much ado you stated: "...higher octane actually helps in any way. It actually accelerates fatigue failure in certain polymers in the fuel train."
No mention of ethanol.
The link you posted takes you to a document titled: "Elastomer Compatibility Testing of Renewable Diesel Fuels". Not sure how's that even relevant unless you own a diesel GX.
I am undoubtedly no expert in chemistry but so far I failed to see how using higher octane gas instead of regular will accelerate wear on polymers or such polymers are even used by Toyota for components built into the GX (as you stated earlier).
No mention of ethanol.
The link you posted takes you to a document titled: "Elastomer Compatibility Testing of Renewable Diesel Fuels". Not sure how's that even relevant unless you own a diesel GX.
I am undoubtedly no expert in chemistry but so far I failed to see how using higher octane gas instead of regular will accelerate wear on polymers or such polymers are even used by Toyota for components built into the GX (as you stated earlier).
the link i posted is a test and results showing polymers differences via chemical reactions. the same polymers are used in many systems. this was about a test and results, and then i added the slight changes used on the gx polymers in test.
i think the rest of the learning on this for polymer chem reactions can be learned outside of this thread.
06-22-23, 07:36 PM
#507
bahahah yes. so the point is that the warranty doesnt reflect whether or not the chem reaction does cause accelerated fatigue. its the design life period that determines a polymers suitability.
the suitability is determined by examining the crack initiation although some use propagation. mass loss is also used. along with a few other checks.
another point is that the octane value of the gas can be higher, just not lower than the declaration. so you might not really know what octane you are getting. more often than not any 87 actually is 89 because theres less total cost to just make all 89 or higher.
this means that the fatigue life of the polymer can be shorter than what we think because we dont know for sure the octane always used.
the epa selects random vehicles both when new and at various mile accumulations, they then run some specific profiles to determine meeting the declarations. the octane is one way to get better values for certain profiles.
the suitability is determined by examining the crack initiation although some use propagation. mass loss is also used. along with a few other checks.
another point is that the octane value of the gas can be higher, just not lower than the declaration. so you might not really know what octane you are getting. more often than not any 87 actually is 89 because theres less total cost to just make all 89 or higher.
this means that the fatigue life of the polymer can be shorter than what we think because we dont know for sure the octane always used.
the epa selects random vehicles both when new and at various mile accumulations, they then run some specific profiles to determine meeting the declarations. the octane is one way to get better values for certain profiles.
06-22-23, 07:38 PM
#508
the epa profile sensitivity aligns with what ASE says about when can you get benefit from higher octane
06-22-23, 07:48 PM
#509
that method is often skipped due to the cost and increased risk. thus the 87 is really 89
06-22-23, 07:53 PM
#510
we used to call it optimum oil refinery gasoline production using linear programming.
i did the math to determine what would be made and sold. the profit loss curve uses a couple overlayed plots of costs, then they are summed across the range, and at the lowest sum you determine what blend to create.
often is saved money to NOT make 87 at all.
i did the math to determine what would be made and sold. the profit loss curve uses a couple overlayed plots of costs, then they are summed across the range, and at the lowest sum you determine what blend to create.
often is saved money to NOT make 87 at all.