Premium fuel 91 octane gains 20 hp / 14 lb-ft torque (vs. 87 octane) on gas engine 2.4L i-Force -- dyno test

[Henry]

This was just posted by STILLEN. Impressive power gains (+20 hp / 14 lb-ft torque) just using premium gas (91 octane) vs. regular gas (87 octane).

BTW Toyota's official specs recommends regular fuel for the 2025 4Runner, so it's absolutely fine running 87 octane.

87 vs. 91 Octane Fuel: STILLEN’s Kyle Millen reveals how fuel octane impacts the Tacoma’s 2.4L turbo engine, showing a 20-horsepower gain with premium fuel. Learn about octane ratings, real-world dyno results, fuel costs, warranty considerations, and why 91 or 93 octane is essential for maximum power, efficiency, and engine longevity—especially with TruControl or other performance upgrades. Don’t miss this must-watch guide for Tacoma owners!​

​

Key Topics Covered:​

​

What is octane, and why does it matter?​

Impact of fuel quality on turbocharged engines.​

Dyno-tested results: 87 vs. 91 octane on the Tacoma.​

Why cheap gas could cost you more in the long run.​

STILLEN's official fuel recommendations.​

 

[olefriend]

Good to know and interesting stats. Nice to see that any 2025 4Runner owner who wants a little oomph can just fill up with premium gas and the factory software will up the power.

Some people might interpret what they say in the video to mean that running 87 octane regular gas is somehow bad for the engine. It's not. Toyota engineers tuned the engine for 87 so I doubt it's making less power due to knock and pulling timing. It's just upping power when it recognizes higher octane premium fuel is being used.

 

[AkiosFavorite]

This video does talk about using 87 might hurt the long term reliability of the engine. I wonder if that's true, will need to see some work truck Tacoma and see if they are able to push to 1/4 million miles with just regular gas

 

[TN Vols]

This video does talk about using 87 might hurt the long term reliability of the engine. I wonder if that's true, will need to see some work truck Tacoma and see if they are able to push to 1/4 million miles with just regular gas

I very much doubt it. I don't think Toyota would be recommending regular gas if it was going to hurt the reliability of the new 4Runner. Like @olefriend mentioned, surely the engineers must have the software/engine tuned so that it runs well on 87 octane, without knock, running rich, pulling timing, and other bad stuff.

 

[AZTrail]

In most cities, regular gas is 87 octane. But cities at higher elevations (>5,000') regular gas is typically 85 octane. Is it OK to use 85 octane at higher elevations?

 

[AkiosFavorite]

I very much doubt it. I don't think Toyota would be recommending regular gas if it was going to hurt the reliability of the new 4Runner. Like @olefriend mentioned, surely the engineers must have the software/engine tuned so that it runs well on 87 octane, without knock, running rich, pulling timing, and other bad stuff.

yeah, there are more and more turbo charged engines these days can run regular fuel and I'm sure it's just fine

 

[AkiosFavorite]

In most cities, regular gas is 87 octane. But cities at higher elevations (>5,000') regular gas is typically 85 octane. Is it OK to use 85 octane at higher elevations?

Nope, that kind of lower octane is okay when naturally aspirated, not when it's turbo charged or super charged, stick with the octane rating required.
Although I won't be surprised if many people didn't know about it and still put 85

 

[qtb007]

Nope, that kind of lower octane is okay when naturally aspirated, not when it's turbo charged or super charged, stick with the octane rating required.
Although I won't be surprised if many people didn't know about it and still put 85

The spec sheet does state "regular" from Toyota. Not sure what the owner's manual will say, though.

 

[Administrator]

The spec sheet does state "regular" from Toyota. Not sure what the owner's manual will say, though.

For reference -- here's what the 2024 Tacoma owners manual say about fuel grade / octane:

You must only use unleaded gasoline.
Select octane rating 87 (Research Octane Number 91) or higher. Use of unleaded gasoline with an octane rating lower than 87 may result in engine knock-ing. Persistent knocking can lead to engine damage.

Source:

Tacoma owners Manual (Gas / non-Hybrid)
Tacoma owners Manual (Hybrid)

Gas engine (2024 Tacoma):

Hybrid engine (2024 Tacoma):

 

[AZTrail]

Here is a detailed explanation on why high compression turbo engines should not use 85 octane gas even at high elevations:

 

[Zaki]

I wonder the hp gain with 93 octane?

If 91 octane vs 87 octane, a 4 octane difference gives a 20 hp gain,
will a 93 octane vs 91 octane, a 2 octane difference give a 10 hp gain?

In other words, will there be a total of 30 hp gain over the 87 octane if 93 octane is used?

I wish Stillen would do that dyno test as well.

 

[WKTJR1]

I wonder the hp gain with 93 octane?

If 91 octane vs 87 octane, a 4 octane difference gives a 20 hp gain,
will a 93 octane vs 91 octane, a 2 octane difference give a 10 hp gain?

In other words, will there be a total of 30 hp gain over the 87 octane if 93 octane is used?

I wish Stillen would do that dyno test as well.

Horsepower gains from octane increases depend on engine sensitivity and diminishing returns. A jump from 87 to 91 octane (4 points) may yield 20 hp, but a smaller jump from 91 to 93 octane (2 points) might only add 5–8 hp. Gains aren’t linear, as engines often reach a tuning limit with higher octane.

 

[Zaki]

Horsepower gains from octane increases depend on engine sensitivity and diminishing returns. A jump from 87 to 91 octane (4 points) may yield 20 hp, but a smaller jump from 91 to 93 octane (2 points) might only add 5–8 hp. Gains aren’t linear, as engines often reach a tuning limit with higher octane.

Ok, that sounds reasonable. Thank you.

 

[TRDBen]

What would be interesting to see is the millage gain using 91 instead of 87. This might offset a bit of the added cost. Not sure how significant. Also sharing my doubts in 87 hurting that engine has Toyota ships it tuned to accept 87, so combustion must be timed right for that octane too. Not a big fan of the testing procedure they used, adding 91 octane on the top of 87.. running the engine a bit to clean the line.. yea but that 91 you dumped in that 1/5 of a 87 tank is now a mix of both.. you could run the engine all day and it would still be a mix result something more like 90 octane..

 

[WKTJR1]

What would be interesting to see is the millage gain using 91 instead of 87. This might offset a bit of the added cost. Not sure how significant. Also sharing my doubts in 87 hurting that engine has Toyota ships it tuned to accept 87, so combustion must be timed right for that octane too. Not a big fan of the testing procedure they used, adding 91 octane on the top of 87.. running the engine a bit to clean the line.. yea but that 91 you dumped in that 1/5 of a 87 tank is now a mix of both.. you could run the engine all day and it would still be a mix result something more like 90 octane..

Good points. They did it the lazy way. They need to burn at least 1.5 tankful's to purge the lower octane and produce more accurate results. Hopefully they or someone else will do a test using stricter testing procedures.