So what exactly happens if you run Premium in a 4Runner?

[Charlievee]

Only engines with higher compression ratios need higher octane gas; the 4Runner is not one of those. Thus there will be no difference in power, or fuel economy.

However, it is more important to use Top Tier Gas as recommended by Toyota and shown in the latest owners manuals (TOP TIER™ Gasoline Brands). Top tier gas has more cleaners in it than fuel that is not top tier, thus your engine will be cleaner, on the inside.

What is the compression? 8:1?

 

[RichinRidgewood]

You have less money for beer

 

[T4R_Canuck]

It makes your wallet lighter or your bank account smaller, not much else.

 

[spartacus]

What is the compression? 8:1?

Dual vvti 10.4.:1

 

[mo_mo]

I did about 7,500 miles over 6 months with 91 vs 87... no measurable MPG change except for the winter/summer blend.

18.8 average before 91 ~ 6 months (watching eco light like a hawk)
18.7 on 91
18.7 post 91 ~ 6 months (added TRD CAI)

 

[Gonecamping]

You have less money for beer

This equates to 4 beers every tank.

I’ll stick with 87

 

[Grape Ape]

At 87, I was getting 14.7mpg, after switching to Premium, I have gained 80hp and get 40mpg!

Just kidding, it doesn't make an f'ing difference. It's a 4Runner, it's horrible on gas and slow, what did you think you were buying?

 

[mrblah]

i skip straight to jet fuel.......

 

[fourrunnerbill]

I used 91 on a Honda Odyssey once thinking it would be better for towing and it it threw up an oxygen sensor code. Never did that again and the code never reappeared.

 

[2021nightshade4x4]

Only engines with higher compression ratios need higher octane gas; the 4Runner is not one of those. Thus there will be no difference in power, or fuel economy.

However, it is more important to use Top Tier Gas as recommended by Toyota and shown in the latest owners manuals (TOP TIER[emoji769] Gasoline Brands). Top tier gas has more cleaners in it than fuel that is not top tier, thus your engine will be cleaner, on the inside.

I see engines with 10.5 require premium fuel, some with 9.6 require mid, so how is the 1GR able to do 10.4:1 with just regular?


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[Hammer0313]

Only time i really see a difference between regular and premium is when im out west loaded down with gear and up in elevation. Not so much on my day to day driving here in the southeast.

 

[BorotHex]

Only time i really see a difference between regular and premium is when im out west loaded down with gear and up in elevation. Not so much on my day to day driving here in the southeast.

What do you notice at elevation? I feel less power and better fuel economy in general here from 5,000’ up. Not sure octane would change that, but curious what you observe.

I have heard others on this forum say they have less head noise and smoother idling on this particular engine with 91. I haven’t tried 87 yet to check into it. I do have access to ethanol free 87 so I may check.

 

[Too Stroked]

Your fuel gauge moves from Empty to Full.

 

[Glenn Goodlett]

I've been running 91 when I am pulling a trailer. I cannot tell any difference.

 

[Jetboy]

I see engines with 10.5 require premium fuel, some with 9.6 require mid, so how is the 1GR able to do 10.4:1 with just regular?


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There's a lot to it. But the simplified answer is that it's a combination of design choices - the shape of the combustion chamber (piston and head), very good cooling system performance, the atomization of the fuel, the relatively low rpm limit, and the tune that runs on the rich side and doesn't advance timing too far. All of those work together to keep cylinder temps low enough that the air/fuel mix doesn't ignite too early. It also doesn't push the performance envelope at all. It never gives you 100% of what the engine could produce if it were tuned aggressively for high octane fuel.

Idle is probably the hardest condition to manage on modern engines. IIRC OV tuning said that half of the entire ECU's fuel map on the Tacoma 3.5L is only used during idle to keep it from knocking. It may be the same for the dual vvti 1GR. Maybe 91 octane will idle better???

 

[08TxRunner]

There's a lot to it. But the simplified answer is that it's a combination of design choices - the shape of the combustion chamber (piston and head), very good cooling system performance, the atomization of the fuel, the relatively low rpm limit, and the tune that runs on the rich side and doesn't advance timing too far. All of those work together to keep cylinder temps low enough that the air/fuel mix doesn't ignite too early. It also doesn't push the performance envelope at all. It never gives you 100% of what the engine could produce if it were tuned aggressively for high octane fuel.

Idle is probably the hardest condition to manage on modern engines. IIRC OV tuning said that half of the entire ECU's fuel map on the Tacoma 3.5L is only used during idle to keep it from knocking. It may be the same for the dual vvti 1GR. Maybe 91 octane will idle better???

Spot on.

 

[patkelly4370]

The higher the octane number, the slower the burn rate.
Instructor at the automotive trade school I attended in 1978 did a demonstration.
In a long (4 foot if I recall) clear tube he atomized a drop or 2 of regular gasoline. Then ignighted it and you could watch the flame front travelling the length of the tube.
He repeated with high octane and the flame travelled significantly slower.

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[Whippersnapper02]

The higher the octane number, the slower the burn rate.
Instructor at the automotive trade school I attended in 1978 did a demonstration.
In a long (4 foot if I recall) clear tube he atomized a drop or 2 of regular gasoline. Then ignighted it and you could watch the flame front travelling the length of the tube.
He repeated with high octane and the flame travelled significantly slower.

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People seem to think a higher octane somehow burns in a way that produces more power simply because performance vehicles require it to make the advertised power numbers. 91 is 4 more than 87 so it's better. :frusty:

I believe it was Sport Compact Car that tested the high octane theory on a 2000s Honda Accord V6 that only needed 87. It consistently lost 10hp at the wheels when running 91.

 

[TEujunga]

Idle is probably the hardest condition to manage on modern engines. IIRC OV tuning said that half of the entire ECU's fuel map on the Tacoma 3.5L is only used during idle to keep it from knocking. It may be the same for the dual vvti 1GR. Maybe 91 octane will idle better???

This makes no sense to me. Knock is load-dependent, and there is no load at idle. I've never heard an engine knock at idle, and that includes old-school carbureted engines with no timing controls and plenty of advance. In fact, the only reason advance mechanisms were necessary before computers was to prevent kicking back during start-up. Once running, the engine could tolerate tons of advance without knocking as long as it was not under load.

The most challenging situation for managing knock is low RPM, high load (i.e., "lugging"). Low RPM, low load with the throttle closed shouldn't be a problem for any engine.

 

[dezertbomber]

Any tests on a dyno or just what is observed? That's what would give us real insight on this.