Premium Fuel or not?

[steeven001]

I don't know if this has been said but on Toyota and Lexus vehicles you can monitor KCLV (knock correction learn value) with techstream or obd devices that support enhanced diagnostics like obdlink.

This value is directly related to the fuel you use and will go up with higher octane and produce more power.

I haven't checked this in the lc250 as it's my father's vehicle. In my Lexus ISF I can get a 5 point increase just from going 91 to 94. Some guys on the ISF forums have done dynos to show the difference KCLV makes.

 

[Obioban]

I don't know if this has been said but on Toyota and Lexus vehicles you can monitor KCLV (knock correction learn value) with techstream or obd devices that support enhanced diagnostics like obdlink.

This value is directly related to the fuel you use and will go up with higher octane and produce more power.

I haven't checked this in the lc250 as it's my father's vehicle. In my Lexus ISF I can get a 5 point increase just from going 91 to 94. Some guys on the ISF forums have done dynos to show the difference KCLV makes.

Is there any way to get values off the knock sensors themselves? Because that would be quite instructive.

As in, if the above KCLV is correctly implemented, there should be no more knock with 87 octane than 94 octane-- just a power/torque/mpg difference. If that is the case, then no reliability/longevity compromise from lower octane.

 

[Obioban]

Watch this video if you still believe that there is no difference in using Premium vs. Regular.
Your LC (and 4Runner) will run on Regular, but it will last (much) longer if you use Premium

This video is about additive packages (fuel brand)-- not octane.

So, not at all related to the topic of this conversation.

 

[steeven001]

Is there any way to get values off the knock sensors themselves? Because that would be quite instructive.

As in, if the above KCLV is correctly implemented, there should be no more knock with 87 octane than 94 octane-- just a power/torque/mpg difference. If that is the case, then no reliability/longevity compromise from lower octane.

There's a knock feedback value (KFV) which is a real time measurement for knock or no knock as the computer tries to advance timing. This number generally only changes under load unless there's some other issues going on.

KCLV is a long term value. You would essentially use this number to compare between running 87 or 91+. Or compare to others lc250. There will be a base number that the computer starts at when you reset or disconnect the battery.

I'm not sure about the lc250 so I'll use my ISF as an example. My ISF has 2 KCLV one for below 3000rpm one for above 3000rpm. The base number is 15 for both. To build up these numbers through normal driving takes a long time. To build these numbers fast you just use manual mode on the transmission selecting gears that will keep you in your desired rpm range and do full throttle pulls. On 91 octane I get this number up to 21. On 94 octane I get this number up to 26.

There is other factors that will effect these values too like temperature, heat soak, oil getting into intake, carbon deposits.

 

[Obioban]

There's a knock feedback value (KFV) which is a real time measurement for knock or no knock as the computer tries to advance timing. This number generally only changes under load unless there's some other issues going on.

KCLV is a long term value. You would essentially use this number to compare between running 87 or 91+. Or compare to others lc250. There will be a base number that the computer starts at when you reset or disconnect the battery.

I'm not sure about the lc250 so I'll use my ISF as an example. My ISF has 2 KCLV one for below 3000rpm one for above 3000rpm. The base number is 15 for both. To build up these numbers through normal driving takes a long time. To build these numbers fast you just use manual mode on the transmission selecting gears that will keep you in your desired rpm range and do full throttle pulls. On 91 octane I get this number up to 21. On 94 octane I get this number up to 26.

There is other factors that will effect these values too like temperature, heat soak, oil getting into intake, carbon deposits.

Sounds like the way to settle this would be to run a couple tanks of 91, to give the ECU a chance to fully adapt the KCLV, and then subject the car to a specific/repeatable load (say floor it up a high with a trailer) and measure the KFV.

Then run a couple of tanks of 87, to once again give the KCLV a chance to fully adapt, and repeat the test on a day with similar climate.

Then compare the KFVs between the two tests, to see if the KCLV is sufficient to prevent any damage from occurring to the engine.

It would also be interesting to see if the base KCLV is different between the Tacoma/4runner (specs 87 octane) and the LC2250 (specs 91 octane). If so, that would be a pretty easy to to change the tune to make the engine factory optimized for 87 (after warranty ends). If not, really shows the 87 vs 91 is just a marketing difference.

What are you using to read/log these values?

 

[katekebo]

This video is about additive packages (fuel brand)-- not octane.

So, not at all related to the topic of this conversation.

This thread is NOT about octane. Look at the original #1 thread-starter post:
"I have seen mixed information. Is premium required or not? What is everybody running? Is there an advantage?"

Some people turned into a discussion about octane rating, but the OP asked about advantages of Premium vs. Regular, which goes beyond octane rating.

 

[Obioban]

This thread is NOT about octane. Look at the original #1 thread-starter post:
"I have seen mixed information. Is premium required or not? What is everybody running? Is there an advantage?"

Some people turned into a discussion about octane rating, but the OP asked about advantages of Premium vs. Regular, which goes beyond octane rating.

Premium is a synonym for high octane:
Google Search: is premium fuel synonymous with high octane
Geico: Premium Gas Vs. Regular Gas
AAA: Premium vs. Regular Gas – Which is Better?
KBB: Should You Use Premium Gas?

From the U.S. Energy Information Administration:

Retail gasoline stations in the United States sell three main grades of gasoline based on the octane level:

• Regular (the lowest octane fuel–generally 87)
• Midgrade (the middle range octane fuel–generally 89–90)
• Premium (the highest octane fuel–generally 91–94)

 

[katekebo]

Premium is a synonym for high octane:
Google Search: is premium fuel synonymous with high octane

From the U.S. Energy Information Administration:

To those who know very little about mechanics and cars, yes. To people who actually know a thing or two about cars, it means much more.

 

[Obioban]

To those who know very little about mechanics and cars, yes. To people who actually know a thing or two about cars, it means much more.

Mechanical engineer that designs car parts here, so I like to think I know something on the topic of mechanics and cars .

If you are conversing about gas, and say "premium", the default assumption is higher octane. Using it for anything else will just add confusion to the conversation, because you're using the term incorrectly.

The Top Tier fuel web site (the additive/fuel quality standard) is careful to not use the word "premium" anywhere (in the consumer facing section or the standard itself), to avoid that exact confusion:

About - TOP TIER™

TOP TIER™ is recognized as a high-quality fuel performance specification developed by some of the leading automotive and heavy-duty equipment manufacturers.

www.toptiergas.com

https://www.toptiergas.com/wp-content/uploads/2025/01/TOP-TIER-Approved-Gasoline_Deposit-Control-Performance-Standard_Rev-G.pdf

 

[EOD Guy]

To those who know very little about mechanics and cars, yes. To people who actually know a thing or two about cars, it means much more.

I know a LOT about mechanics and cars, I'm very familiar with octane levels, detergent packages, combustion and flame fronts............ I associate high octane with premium or Hi-test and low octane with regular.

 

[imann777]

There are too many factors involved in Getting a better gas mileage. Just not filling the Higher Octane. I just dont believe this snake oil conspiracy marketing.

 

[EOD Guy]

If there's a sticker on the fuel door ......... one must comply without question!

 

[JDD]

Toyota says premium. I'm going premium. These aren't cheap vehicles, so I won't be saving a couple of bucks trying to find out whether lower octane actually works.

Absolutely agree. US Average difference in price per gallon is $0.50 - $0.75 from 87 to 93. So roughly $9-$12 more per tank full of Premium. Personally I feel the savings are too small to risk on a $60k - $70k vehicle.

 

[EOD Guy]

Mookie242 in another post on the same subject, had this to say:

"I'm still getting close to 23mpg with mainly regular gas. Am I missing out on "optimal performance" with premium gas? I don't seem to be. Sheldon Brown, Toyota's chief engineer, was on TRD Jon's podcast and said the new Land Cruiser engine will do just fine with lower octane gas. He said the reason they labeled Land Cruiser "premium preferred" was because it was more global in nature and kept it the same as the outgoing Land Cruiser. He also conceded it's basically the same powertrain as other regular gas Toyota models. The difference is that these models are marketed towards just the North American market where as they wanted the Land Cruiser to have a singular global standard and, thus, settled on keeping the premium preferred approach."

There doesn't seem to be a mention of the fuel door sticker, so it may false information.

 

[cvx5832LC]

This thread is NOT about octane. Look at the original #1 thread-starter post:
"I have seen mixed information. Is premium required or not? What is everybody running? Is there an advantage?"

Some people turned into a discussion about octane rating, but the OP asked about advantages of Premium vs. Regular, which goes beyond octane rating.

From Costco Gasoline's FAQ, and I imagine everyone else does it this way, since Costco does not manufacture gasoline. Aka this thread is a discussion on octane.

https://www.costco.com/gasoline-q-and-a.html

 

[ultane]

In my Lexus ISF I can get a 5 point increase just from going 91 to 94. Some guys on the ISF forums have done dynos to show the difference KCLV makes.

My oldest son had an ISF for a while.. it was wicked quick.

 

[Captain Trips]

 

[surf fishing offroader]

I skip all that "octane" gasoline bs and just pour in orange juice

High pulp, tropicana only, none of that sunny d crap

I hear some people on fb run apple juice, to each their own I guess

 

[ultane]

View attachment 28493

Dammit.. you owe me a keyboard!!!