Premium Gas?

[RickC]

You can search fuel mileage ratings at Fuel Economy for just about every car out there back to 1984 year model. Just click "Find a Car", then "Search by Make", then select the year and brand. It will not only tell you what the mileage ratings are, but off to the right, will tell you whether it requires "regular" or "premium".

 

[skyykeeper]

I live in CA, and the price right now of regular is about $3.75 and premium is $3.95. I get a little better mileage in my 04 Limited V8 with the premium fuel. So I buy it. The cost difference is about $4 per tank more to run premium, so I don't sweat it. The real problem is when the OVERALL gas prices swing high. But if you're only paying about $.20 more per gallon for premium, an extra $4 per tank for better mileage is fine with me. Plus, I think it runs smoother, but that's just my opinion.

 

[SC Joe]

i had better fuel econ with 91 octance as compared to 87

I actually get better gas mileage with 89 than 87 or 91 in my '05 V8 2wd.

 

[BlackWorksInc]

Lemme throw a wrench in on that reliability/performance to straight performance argument.

2001 Twin Turbo Supra with 300k+ no rebuild, runs great... just had it in today at the dealership.

 

[Jeff S.]

BC you live in Denver I assume. At the higher altitude, 85 operates as well as 87 or higher. You will find 85 as an option in places with high altitude.

I wouldn't worry.

I just moved to Bozeman, and regular is 85. The catch is, Costco, where I usually get gas, only has 85 and 91.

Bozeman is the same elevation as the town from Nevada from which I came, and regular was 87, so I'm leery of switching grades.

Guess I have to find a station that sells 87.

 

[Eastcoastrunner]

Lemme throw a wrench in on that reliability/performance to straight performance argument.

2001 Twin Turbo Supra with 300k+ no rebuild, runs great... just had it in today at the dealership.

they made a supra in 2001?????:gun6:

 

[Atlanta_man]

miss my '79, '83, and '84 Supra's

took the '84 to 240K mi
only replacements were bumper, hit from behind and the p.s. rack up front.
did both in my driveway

 

[BlackWorksInc]

they made a supra in 2001?????:gun6:

Oops... my bad... dunno what I was thinking there. Its a 15th Aniversery edition so its a '97 and we actually made the Supra until '02 but imports to the US stopped in '98

 

[Vantage85]

Wow, a lot of misinformation around here regarding the use of premium fuel.

The main 2 factors that contribure to using 91+octane fuel are:


1) Compression Ratio.


2) Forced induction (Turbo, SC, or Nitrous).


I believe the CR for a 4.0L v6 is 10.0:1, which should use 91 octane.

The v8 on the other hand has a CR of 9.6:1.


A higher CR (anything over 10.0:1) In my opinion should be used with premium.


The reason people can get away with regular on a high CR motor is becuase the motor was tuned very safely.

If you had a more performance minded car (like a Civic DOHC Vtec or iVtec) with a much narrower safety factor, the premium gas is manditory to ensure there are no engine problems such a "pinging".

The same goes for boosted cars (WRX's, GTI ect).


These are just my estimates but:..



12.5:1 + CR or big PSI turbo= 94+ Octane
10.1:1 - 12.5 CR or turbo = 91 Octane
9.5:1 - 10.0:1 = 89 octane
9.5:1 and lower = 87 octane.

Just a guideline, and that being said my 4.7 see's 87 octane for 80% of its life.

 

[SC Joe]

Wow, a lot of misinformation around here regarding the use of premium fuel.

The main 2 factors that contribure to using 91+octane fuel are:


1) Compression Ratio.


2) Forced induction (Turbo, SC, or Nitrous).


I believe the CR for a 4.0L v6 is 10.0:1, which should use 91 octane.

The v8 on the other hand has a CR of 9.6:1.


A higher CR (anything over 10.0:1) In my opinion should be used with premium.


The reason people can get away with regular on a high CR motor is becuase the motor was tuned very safely.
If you had a more performance minded car (like a Civic DOHC Vtec or iVtec) with a much narrower safety factor, the premium gas is manditory to ensure there are no engine problems such a "pinging".

The same goes for boosted cars (WRX's, GTI ect).


These are just my estimates but:..



12.5:1 + CR or big PSI turbo= 94+ Octane
10.1:1 - 12.5 CR or turbo = 91 Octane
9.5:1 - 10.0:1 = 89 octane
9.5:1 and lower = 87 octane.

Just a guideline, and that being said my 4.7 see's 87 octane for 80% of its life.

You missed some parts about the engine ret@rding its ignition timing and changing the fuel curve when it senses spark knock.

 

[JB.]

V8 '05 and up is 10-1 compression ratio.

 

[Kokoman78]

I feel everytime I added premium gas my MPG has always been better... I've always used premium... I feel a smoother ride and better MPG then when I put regular

 

[Daddy4Runner]

03 v8 here.

I try to run 94 octane when gas isn't over $1.50 a liter.

Definitely use premium on any roadtrips for the slight MPG increase and/or increased top speed

 

[m85476585]

The GX470 requires premium, oddly enough. I think it's rated for 5hp more than the 4runner V8.

A higher CR (anything over 10.0:1) In my opinion should be used with premium.


The reason people can get away with regular on a high CR motor is becuase the motor was tuned very safely.

Your opinion is wrong. If an engine is properly engineered, high compression ratios don't require premium fuel.

Here's a great article about some of the things Mazda does to get their engines to run 14:1 compression ratio. I think they lower it to 13:1 for US regular fuel, but that's still notably higher than other vehicles. Most of it comes down to lowering the temperature at maximum compression.
MAZDA: SKYACTIV-G | SKYACTIV TECHNOLOGY

Direct injection is another thing that helps an engine with higher compression ratio run on regular gas.

To be fair, I think Mazda's engine was announced after the quoted post was written.

 

[TheWhite4Runner]

So my parents are looking for a 4th gen. Here's the catch- my dad thinks it requires premium fuel in the V6. I know, search, but he needs to hear it from the horses mouth. So what fuel is needed in the 4runners?
Thanks,
Jeff

I run 93 in my 2004 4runner because i had problem with my O2 seniors running 89 and once i put the higher octane in the light went away. But premium gas is recommend but you can use lower octane and be fine.

 

[4RunnerPossibility]

I would think just 87 but I'm no expert.

 

[bob3dsf]

It's aliiiiiiive!!!!!! [emoji41]

Sent from my SM-G920V using Tapatalk

 

[Keros]

The GX470 requires premium, oddly enough. I think it's rated for 5hp more than the 4runner V8.




Your opinion is based on decades with of experience and established "rules of thumb" in the automotive industry.

However, with the radical new redesign of the traditional Spark Ignition Internal Combustion Engine from the ground up, transforming it into a compression assisted spark ignition internal combustion engine using technology developed by a largely obscure, small manufacturer, with only ~2% market share in North America... high compression ratios (13:1+) don't require premium fuel in engines using this new technology.

Here's a great article about some of the things Mazda does to get their engines to run 14:1 compression ratio. I think they lower it to 13:1 for US regular fuel, but that's still notably higher than other vehicles. Most of it comes down to lowering the temperature at maximum compression.
MAZDA: SKYACTIV-G | SKYACTIV TECHNOLOGY

Direct injection is another thing that helps an engine with higher compression ratio run on regular gas.

To be fair, I think Mazda's engine was announced after the quoted post was written.

Fixed that first paragraph for you.

Anyway, by definition the efficiency of the Otto Cycle is a function of the compression ratio. Of course this means that finding a way to run a gasser motor at a higher CR with average fuel is getting cake and eating it too. Free Lunch, etc.

Realistically though, people still put diesel in gas engines and gasoline in diesel engines, causing all kinds of mayhem: We, the average consumer, can be very stupid. There's no way any automaker can put a car on the market that 87 octane is going to cause problems to... 'cuz people will mess it up and blame the manufacturer. So, engine design and tuning will forever be strapped to this problem.

Apparently Toyota has taken quite an interest in SKYACTIV, so perhaps we'll see it in future models.

In any case, my V8 tends to have a bit more ZIP to it on the second tank of 91 or 94 octane. Not much, but it's noticeable. Pretty fun for a little treat once and a while. High octane allows any motor with ignition timing and/or valve timing to run full advanced tuning.

Although it may be a bold statement, I think it's safe to say every car sold in North America has adequate "slush factor" built into its tune to retard timing as needed to run 87 octane safely. Further, any, most and perhaps all of those engines will probably run better on higher octane fuel, resulting in using more timing advance.