Higher octane vs lower octane gas

[mitre]

Hi,

Just picked up my 2004 4runner and the owner said he put in mid grade (89) gas.

I wanted to know if changing now to regular (87) would be bad for the engine. The car has 119,500 miles? Should I just keep putting in mid grade gas?

I've read the threads about fuel efficiency but wasn't so sure about how switching fuels would effect the engine.

Thanks,

 

[mrrab]

I've used both 87 octane and 89 octane (10% ethanol) and can't tell a difference in performance and fuel efficiency.

I'd say go with the cheapest...

Nice Limited.

 

[Synister]

I ran premium for over a year after I first got my truck, mostly because gas was pretty cheap. I now run 87 and have done so for the last 25k or so. I notice essentially zero difference and the manual says 87 is g2g. Wikipedia lists 3hp and 12 ft lb of torque increase when comparing 87 and 91 in the 1gr-fe V6, both at RPM's I rarely see. Bottom line, you wont hurt a damn thing with 87, your engine was built for it. You will find people that swear by premium, mostly for peace of mind.

 

[mitre]

Thanks for the quick replies. Great forum.

 

[bensanders]

I switched to premium for a little while. I'm sure it makes a small difference but I didn't notice one, so I went back to regular. Toyota would spec that out if it was necessary.

 

[sr5hi]

Congratulations on your purchase. I have used regular grade gas in my 2003 V8 from day one without any problems. If you have engine pinging (detonation), then you need to use higher octane fuel or you risk engine damage.

 

[Redstone8]

I have an 05 Sport V6 and I have been using regular in mine since 18,000 miles. Now 4 years later at just over 66,000 no problems at all.

 

[ClockWork]

I notice a performance and mileage improvement with 93. So much so that it pays for itself. I run V-Power in all my cars.

 

[MikeInNH]

I switched to premium for a little while. I'm sure it makes a small difference but I didn't notice one

It'll make ZERO difference...Sorry but it was a waste of money.

If your engine is designed to run on 89 Octane then running with a higher octane is complete waste of money. It is NOT a Premium gas....as the gas companies say. Fuel's octane rating relates to how much energy it takes to ignite that fuel. The higher the octane the more energy it takes to ignite the fuel.

The performance issue that comes into play is when you use a lower octane then the engine was designed for. Usually this will be noticed on hard acceleration. When accelerating and using a lower octane it may cause the engine to knock. The engine monitoring system should detect this knock and then re**** the ignition timing. This will result in lower performance and decrease fuel economy.

The other problem with running at a lower octane (although it's very very rare). Is if there's a problem with the anti-knock sensor. If there is and you accelerate hard that causing pinging.....it could destroy your engine. Not very likely to happen....but it could.

 

[DC runner]

Lets break it down, as it is actually 2 different things. Clockwork is right, in that, at a certain price point; higher octane will pay for itself. That said, it is heavily price dependent.


1. Is it safe. Yes.

2. Is is "better". No and Yes. 1. It has no more "power" than regular gasoline. BUT because the engine does not have the modify the cycle due to higher grade anti-knock additives, you are able to "access" more of the stored potential power.


It is a price issue. If the price difference between 93 and 87 is lower, which happens due to the way fuel is priced and delivered, then it would probably come out on top.

If it happens to be a time when premium is swinging far above regular, then no. The price point difference is too great.

In general... on modern cars, it makes little difference. Our engines do not have a high enough compression ratio and a very complex ECU and knock system to more than make up.

 

[bensanders]

It'll make ZERO difference...Sorry but it was a waste of money.

If your engine is designed to run on 89 Octane then running with a higher octane is complete waste of money. It is NOT a Premium gas....as the gas companies say. Fuel's octane rating relates to how much energy it takes to ignite that fuel. The higher the octane the more energy it takes to ignite the fuel.

The performance issue that comes into play is when you use a lower octane then the engine was designed for. Usually this will be noticed on hard acceleration. When accelerating and using a lower octane it may cause the engine to knock. The engine monitoring system should detect this knock and then re**** the ignition timing. This will result in lower performance and decrease fuel economy.

The other problem with running at a lower octane (although it's very very rare). Is if there's a problem with the anti-knock sensor. If there is and you accelerate hard that causing pinging.....it could destroy your engine. Not very likely to happen....but it could.

I like how you state there is "ZERO" difference between the two before spelling out two differences. Terrible logic.

 

[MikeInNH]

I like how you state there is "ZERO" difference between the two before spelling out two differences. Terrible logic.

Re-read it...But try to understand it this time.

There IS a difference IF AND ONLY IF your vehicle IS DESIGNED to run on premium.

Since our engines are NOT designed to run on premium...then it'll make ZERO DIFFERENCE.


I can draw you a state-diagram if you want.

 

[Baja Runner]

Higher octane fuel is simply made for engines that run a higher compression. If the manufacturer states that it needs a higher octane fuel, then you use it. Engines that do not run at a certain level of compression will not benefit from the higher octane and thus is a waste of money.

Thermodynamics tells us that a higher compression ratio is directly related to the thermal efficiency of the motor. That is why manufacturers are designing for higher compression, and why higher octane gas is there so it won't pre ignite before the spark. That is also why you need to run high octane with a Turbo or supercharger. Its not because it burns cleaner.

 

[bensanders]

I switched to premium for a little while. I'm sure it makes a small difference but I didn't notice one, so I went back to regular. Toyota would spec that out if it was necessary.

See how I already mentioned that? Also, you CAN italicize things INSTEAD of CAPITALIZING every OTHER word.

Anyways, the point is there's no need to run anything other than regular, so we agree on that.

 

[MikeInNH]

See how I already mentioned that? Also, you CAN italicize things INSTEAD of CAPITALIZING every OTHER word.

Anyways, the point is there's no need to run anything other than regular, so we agree on that.

Actually NO.....You took MY comment out of context. You didn't post what I was commenting on. Anything can be completely misunderstood when taken out of context.

When I said "It'll make ZERO difference...Sorry but it was a waste of money."

I was commenting to what you said earlier....

"I switched to premium for a little while. I'm sure it makes a small difference but I didn't notice one ".

And I stand 100% behind that....It'll make ZERO difference for the 4runner since the 4runner engine is NOT designed to run on higher octane.

It will however make a difference for vehicles that ARE designed to run on higher octane.

Sorry...better luck next time.

 

[bensanders]

Look guy, if you think it makes literally zero difference using regular vs. premium then you're a moron. I realize it may not be very noticeable and our engines aren't designed to run the fuel, but the engine will still behave differently, deposits will build up differently, gas mileage can change, etc.

What do you say to people who claim they see a noticeable difference, whatever that difference may be?

 

[jwyshrek]

When all else fails, just refer to the owner's manual...

2004 Toyota 4Runner owners manual, page 274:

OCTANE RATING
Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with Octane Rating of 91 (Research Octane Number 96) or higher is recommended.


I've heard that the 'improved vehicle performance' allows the engine to make the rated HP, so with 87 you'll make a few less, but nothing noticeable (I believe).

Oh, octane rating affects the engine's spark timing...advance and re****...thereby affecting the power that can be made...the power band. But does a difference of 4 octane make a difference?

Now I can see a difference between 87 octane and 100 octane (aircraft fuel)...if you could play with the the timing...it might be fun...

 

[jwyshrek]

Hmmm...the forum blanked out T A R D...but that's the terms that's always been used...advance and re t a r d timing...

Anyway, the 4runner (like many other vehicles) can adjust its timing based on various variables, sensors and conditions...so I'm sure it can sense which fuel is being used and adjust accordingly (up to a limit of course).

 

[liqourish]

Hmmm...the forum blanked out T A R D...but that's the terms that's always been used...advance and re t a r d timing...

Anyway, the 4runner (like many other vehicles) can adjust its timing based on various variables, sensors and conditions...so I'm sure it can sense which fuel is being used and adjust accordingly (up to a limit of course).

:cheers: I run 89 or better(on good a good payday)

 

[RonMAIDEN]

What do you say to people who claim they see a noticeable difference, whatever that difference may be?

I think for the most part people are just trying to justify the extra money they spent on premium. I don't see how people can truly feel a difference in power since the increase is so small. Unless you have dyno numbers or consistent results from better acceleration like at a dragstrip then you could see a diff on paper but most people are imagining they are feeling a difference.
And differences on MPGs is more dependent on how you drive and not octane rating in a naturally aspirated 4runner V6 or V8.