Question re: Octane requirements for new Toyota

[demarpaint]

Hi and thanks in advance:

I was looking into a new Toyota FJ cruiser and much to my disappointment it calls for 91 Octane Gas. I was told it can run on 87 Octane, but it would give up some HP, that the computer can compensate. My feeling is it will cause problems with the 87.

It there any truth to this? Will MPG suffer with 87 Octane. Or is it B#@$%it! and the truck must run on 91 Octane?

Thanks and Happy New Year.
Frank D

 

[Chris142]

If it's designed for 91 running 87 will cut the power and mpg a little. The more timing the better mpg, to a point. When it retards the timing for the 87 the mpg will drop.

 

[demarpaint]

Thanks, will the 87 damage the engine at all?

Frank D

 

[Kestas]

Who told you it can run on 87? If it was the owner's manual, then I'd say you have no worries.

A car that is designed to run on high octane, but can also use 87 undoubtedly has a knock sensor on the engine. The knock sensor adjusts the spark for optimal timing "on the fly" for the fuel that is being burned at the moment. This prevents damage to the engine from using low octane gas.

Use 91 octane for best fuel efficiency and performance.

 

[demarpaint]

I read it called for 91 Octane, while surfing the www. A buddy and I were discussing it and he had taken a test drive a few weeks back and was told by the salesman it would run on 87, but lose a few HP.

I thought it was #@$%!, and if it called for 91 then that's all you should use. I heard from other people that the new computers could adjust for Octane so it had me wondering.

My wife and I are considering buying one but would rather not put 91 Octane Gas in it. That's why I asked. If it will only run on 91 Octane, we'll look for another vehicle.

Thanks for the replies,
Frank D

 

[JohnBrowning]

It is typical on todays more modern vechiles. They are more flexable then then they were in the 1980's! The sales man was telling the truth!

 

[Kestas]

I don't understand your aversion to 91 octane. Sure it costs more at the pump, but all things being equal you'll benefit from better gas mileage.

Should you decide to get this Toyota, putting in 87 octane is false economy. Whatever you save at the pump will be lost in gas mileage as the computer "detunes" your engine.

One interesting observation about the higher octanes, the 87/89/91 octanes have always historically been in 10¢ increments, regardless of the price of gas. That means when gas was around a dollar, they were in 10% increments. Now at $2 a gallon, they're now only at 5% increments, making higher octane now a better bargain than ever before for the cars that use it.

It sounds like your salesman is very knowledgeable and forthright with you about this.

 

[wantin150]

My 03 Matrix calls for 91 or higher. The manual says that 87 "may" be used short term if 91 or higher isn't available but you should go back to the 91 as soon as possible after. IMHO, use what the manual calls for.

 

[gedcruise]

Maybe Toyota can get Honda to help them with engine design, since nearly all Hondas are happy with 87 octane, and are usually more powerful than comparable Toyota engines to boot.

 

[demarpaint]

Thanks for all the replies, Happy New Year!

Looks like I might just pass on the Toyota this time. We are looking at .30/gallon or more for the 91 Octane gas. I've had v8's run on regular gas just fine. Maybe in 2008 Toyota can get this truck to run on regular gas. It just doesn't add up for me.

+1 gedcruise

Frank D

 

[Ferndog]

Building on some prior posts, most of today's cars have knock sensors and most are reactive instead of proactive. If you car needs 91 and you put in 87, the knock sensor will retard the timing to stop the knocking. Less timing = less performance which can impact fuel economy depending on how you drive. So the salesman was right - but at the expense of reduced performance.

If you had a different car and it called for 87 and you opted to put in 91, most cars will see no difference in octane performance. But some cars with proactive knock sensors, like the higher end performance cars, will continuously alter the timing to see if they can increase performance should you happen to put in higher octane gas or be driving in conditions where your engine's octane appetite may be temporarily lower.

One last plug for higher octane - some gasoline brands put more detergency in their premium grades which can have a beneficial impact cleaning the induction system which can improve driveability and performance.

 

[ChrisW]

just for kicks i'mma try and run a tank of 100 unleaded in my 94 civic and report back here. $4/gallon here I come...
In engines w/o knock sensors (and even ones with), I'd say base the octane primarily on the compression of the engine; higher the compression higher the octane.

 

[ted s]

dont be surprised with a lower MPG

 

[gedcruise]

Not necessarily. Combustion chamber shape can have as great an influence on an engine's octane requirement as compression ratio. Also, the calculated compression ratio is not the end of the story. Valve timing overlap must also be considered.

 

[Quest]

My Fit calls for 87 octane and even though it has 10.3:1 compression and I gave 92 octane a try already(actually like 3 tankfuls areadly), no noticeable fuel economy nor performance improvements perceivable.

 

[Eddie]

Believe your owners manual and NOT a salesman.

 

[Bryanccfshr]

I have two of the exact same engines as is in the FJ and I run 87 Octane exclusively. I track the mileage and see no improvement when I did try premium for regular driving( I tried real hard to jestablish if premium fuel was justified for effeciency but saw no measurable difference in mileage, so those who claim there is a mileage improvement just don't know this engine.). For towing or doing high load driving the premium may allow better performance but my wifes 4 runner and my Tacoma live off of 87 unless I am hooking up to a trailer (then I go premium so I can pull hills with less downshifting). There is no difference in regular driving as far as mileage is concerned.

The 91 Octane is what was used to get the listed Horsepower and torque ratings. The timing will retard a little with less octane netting less total power. But as I mentioned, for day to day driving how often do you require 100% of the rated Horsepower? For me it's never.

The owners manual will state that 87 octane is the minimum octane rating and that 91 is recomended for maximum performance. So read the owners manual and rest assured that 87 octane is fine.

 

[demarpaint]

Thanks for all the replies. Seems 87 Octane should work, I spoke to a Toyota Serivce tech and he basically said what has been mentioned here. For towing and HD use, 91 Ocatane gas works best, for normal driving, which is what we will use it for 87 Octane will be fine.

Thanks
Frank D

 

[Quest]

With technological advancements in terms of engine designs and executions, it is not impossible to have high compression engine previously impossible w/o hi-test gasoline to run on 87 octane these days.

Even though my fit bears a 10.3:1 compression ratio which theoretically calls on hi-test gasoline (higher than that of 87), but with knock sensor, distributor-less ignition and full computer ignition mapping and control, it is "smart" enough to adjust to various fuel octane w/o users to worry about it.

given such advancements, I wouldn't be surprise that Honda can casually change the ignition mapping and fuel requirements to meet all kinds of different fuel types, inc. E85 by simply uploading a different program into the ECU.

My 2c's worth.

p.s. I found out that my car runs better using Texaco 87 octane gas than a few other varieties (currently using Chevron for it's Manganese-free)

 

[widman]

Your signature doesn't say what part of NY....... The higher you go into the mountains, the lower your octane needs. That is why I could run my Grand Cherokee on 80 octane after a couple of Techron treatments to clean the carbon out. That was before I discovered who I could pay off to get Aviation Gas.