Gas prices/Octane rating required?

[SWUtah]

With the price increase I am considering burning regular versus premium in my 99 LC. It saves over $ .20 per gallon. The problem I have is that as well as the engine compartment is insulated in the 100 series I'm affraid I would not hear pinging if it occurs. Did a search and found this link that indicates that you are wasting your money using premium http://www.toyota-4runner.org/showthread.php?s=&threadid=683

Comments

 

[moooooooo]

I watched an episode of 5th Gear on UK TV here on FoxTel (pay TV) and they did a comparison using a Subaru WRX measuring performance.
They did three tests using standard, premium (96 Octane?) and 98 octane also using 3 different suppliers. BP, Shell and i can't remember the third.
After each test they reset the cars computer so that the computer would re-calculate the tuning and everything else it does.

They found that Shell Optimax (98 Octane) boosted performance significantly and the HP output of the engine increased by using it.

I know this doesnt answer your question about pinging, but it's something to be aware of.
cheers
peter

 

[jhkilmer]

Gas

I have a 99 also, and I always run 89 octance, and I've found that it runs perfect. I have run 86 and 87 in the past, and noticed a difference. Plus with the mid-grade fuel, here in the US, they just mix regular and premium (50/50), so your actually getting half of the detergents from the premium. Plus, much of the time I can find a gas station where the price different between regular, and mid-grade is only 5 cents. 89 is the lowest that I'd recommend, IMO.

 

[ShottsUZJ100]

I can tell the diff in my 01 with reg. It rides like a V6 after about 50 miles. The engine does sense octane quality and adjust. About 50 miles back with premium the thing perks back up.

 

[SWUtah]

Here in Utah they sell 85 regular and the premium is 91 octane. I guess at 5000 ft. the octane can be lower???

 

[ATLcrusher]

You're quoting a post from Thai??? Oh boy they'd have a party with this over on chat.

 

[SWUtah]

You're quoting a post from Thai??? Oh boy they'd have a party with this over on chat.

They always have a party in chat

 

[Pskhaat]

Higher alt means less O2 by volume means less volatility thus fuel can be more volitile and thus lower octane rating.

 

[rockclmbr]

Here in CA I've run regular 87 octane without any noticeable effects in performance, idle, etc. I'll stick with it as it is cheaper and my 100 likes it.

 

[Pigeon]

When your talkin 3 bucks a gallon - 20 cents is not much at all.
On a 20 gallon fillup your at $56 for 87octane or $60 for 93octane .
If you gain only 1mpg on a tank - that will pay for your premium.


When ever I put regular in my Acura the engine pings right away.
I have run 87 in my LC and it never pings, although its such a slug as it is I want to get as much horsepower as possible.

 

[Jim_Chow]

The 100 won't ping, but you'll have to use more accelerator up the hills and from a dead stop, so that cancels your gas savings. When I went from 87 to 91, it felt a lot more peppy. On 87 in the hills, it's definitely anemic (this is with 300 lbs of passengers incl driver, no other weight)...I'd say slower acceleration than my 20 yr old 4-cyl 4runner with the same load (heavy and underpowered w/ ARB/Kaymar/sliders, modified exhaust). If you're driving on a flat freeway at a constant speed, I don't think you'll notice a huge difference unless you try to pass someone, or are carrying a bunch of passengers/gear. But if you're worried about a $4-5 difference per tank between premium and regular, shouldn't you consider something like a prius as a commuter? I only use the 100 on the weekends for R&R, so if it gets only 15mpg, it doesn't bother me, as I'm having fun with it. Isn't this what it's all about? Last thing I want is to think about is the "cha-ching" of the cash register while driving...

 

[SWUtah]

The 100 won't ping, but you'll have to use more accelerator up the hills and from a dead stop, so that cancels your gas savings. When I went from 87 to 91, it felt a lot more peppy. On 87 in the hills, it's definitely anemic (this is with 300 lbs of passengers incl driver, no other weight)...I'd say slower acceleration than my 20 yr old 4-cyl 4runner with the same load (heavy and underpowered w/ ARB/Kaymar/sliders, modified exhaust). If you're driving on a flat freeway at a constant speed, I don't think you'll notice a huge difference unless you try to pass someone, or are carrying a bunch of passengers/gear. But if you're worried about a $4-5 difference per tank between premium and regular, shouldn't you consider something like a prius as a commuter? I only use the 100 on the weekends for R&R, so if it gets only 15mpg, it doesn't bother me, as I'm having fun with it. Isn't this what it's all about? Last thing I want is to think about is the "cha-ching" of the cash register while driving...

Money is a factor if it's not buying me anything. I live at 5000 ft above sea level and this area goes from 3000 to 9000 within a 30 mile distance. So your post helps a lot when it comes to deciding if I should continue to use 91 or go with the 85 octane. Thanks for the insight.

 

[Jim_Chow]

BTW, I'm at 3K ft. Since you're at such a high altitude, I'd experiment with different octanes to determine what you really need. My guess at why a higher octane works better at higher altitude is (and anyone correct me if I'm way-off base) the delayed ignition of the premium allows more air to mix w/ the fuel, and lack of air is what is hurting one the most at those altitudes. What would REALLY help is some kind of forced induction (turbo, S/C, nitrous-oxide), but you'll almost certainly have to use premium all the time to take advantage of it.

 

[sJs]

FWIW, I've never put anything greater than 87 octane (low altitude in the southeast, i gues your equiv is 85) in my 99, and i've never noticed any pinging. That being said, my truck might feel a bit sluggish (ie not too 'peppy', as others called it) but in all honesty if you folks are distraught over the flux in acceleration due to different octanes, then this defenitely is the wrong vehicle for you.

That being said, i make pretty good gas mileage on the highway, between 17-18 mpg. I might drive like a grandma ( low 70s mph or less), but i still get good fuel economy and enjoy the heck out of my truck

 

[SWUtah]

My biggest concern is that I don't want to harm my engine by running 85 octane. Performance is not a factor but if the lower octane lowers my mpg then it might not be worth it. Anyone have the answers??

 

[tabraha]

I can't really tackle whether 85's gonna hurt the engine or not but I've expressed my line of reasoning against regular in my 100 in the other gas mileage thread, definitely check out the info in that thread. I'll try not to repeat myself too much. Everyone's vehicles are different even among vehicles of the same model. sJs in post #14 states he sees no difference in reg and prem in his 100 yet I do see a difference and we are both in 99's and even live within 60 miles of each other! It is definitely determined on a vehicle by vehicle basis.

Assuming you can run 85 w/o problems, I think it will still be more expensive to run it vs. premium. If your 100 is on the cusp of coming out of OD to pull hills then it is DEFINITELY going to come out of OD more frequently on the dirt gas. If you get less time in OD then it's gonna be a wash; at best and possibly more expensive! When I run towards the mountains my increased time out of overdrive makes the spread between reg and premium jump to 3mpg difference, not to mention increased rpms etc...

Remember @ 15,000 miles per year, 15mpg, .$20 more per gallon = $200 a year more AT MOST. Any adverse effects such as slowly clogging the injectors a gradual mpg drop etc..., whether you notice them or not will reduce the $200 and could possibly cost more money. I've definitely found it to be less expensive for me to run premium based on my own MPG differences with a loaded up vehicle.

I can't emphasize enough how important it is to test your own vehicle's reaction rather than believing all of the articles, including all of what I've just written above. Most of the magazine articles aren't too well researched and talk in terms of trends rather than specific cases. Some articles just outright call premium gas "snake oil" but I have a hard time believing that the placebo effect can effect mathematics so I do my own calculations. In conclusion again it is best determined on a case by case basis. I run regular in my Tacoma all day long b/c it is the right fit for it but I made sure it was first.

Hope this helped some.

 

[Jim_Chow]

The key is high-quality gas. I ran chevron 91 exclusively in my old 4runner for years. I then tried the Redline fuel conditioner at $6/bottle, ran a couple of bottles...didn't notice any difference in performance or fuel economy. Also changed my fuel filter w/ an OEM one as a precaution since the original one had 140K mi on it. Again, noticed no difference. Had the injectors checked. They were fine (still okay at 20 yrs, never had them cleaned, no bg44k). One could save 20 cents/gal and run cheaper gas, but in the long run, you might have to pay the piper years down the road and rely on expensive fuel treatments, new injectors, etc.

 

[NMuzj100]

Higher alt means less O2 by volume means less volatility thus fuel can be more volitile and thus lower octane rating.

Octane is not a measure of volatility. Diesel fuel is less volatile than gas but much more resistant to compression combustion. The same fuel is more volatile at a lower atmospheric pressure but its response to pressure in the cylinder will be the same. What changes at altitude is the peak pressure in the cylinder.

lower atmospheric pressure = lower air density = lower cylinder pressure at peak compression = reduced octane requirements at altitude (no effect on power)

lower atmospheric pressure = lower air density = less O2 by volume (means less fuel can be fully burned with each cylinder cycle = reduced power output)
​

these are two seperate effects of altitude.

Those more knowledgeable please fine tune or correct this understanding.

The problem I have is that as well as the engine compartment is insulated in the 100 series I'm afraid I would not hear pinging if it occurs.

You needn't worry about pinging. The computer will not allow it. It will adjust the timing to eliminate pinging.

I also think the question of gas quality and detergent amounts is seperate from the octane ? Regular is not more likely to cause deposits than premium. But low-detergent gasoline (regular or premium) is. Shell does advertize more detergents in premium than regular but Chevron does not. Both are "Top tier" ( www.toptiergas.com ) producers.

 

[Pskhaat]

Octane is not a measure of volatility

No you're right, its actually a measure of how fast the flame front should consume the fuel-air mixture based on measured value to a mixture of isooctane and n-heptane. Diesel though has about 15% more energy per volume measurement than gasoline...but I digress and I guess it would be significantly less `volatile' to combustion.

What changes at altitude is the peak pressure in the cylinder.

But even forced induction systems perform worse at higher altitude. And I failed too many chemistry courses at Uni to make too fine a statement so could be WAY off here, but the partial pressures of the various gasses should change percentages with lower pressure and by volume you should get less combustible particules, no?

You needn't worry about pinging. The computer will not allow it. It will adjust the timing to eliminate pinging.

Hopefully the 100's computer is better than the 80's, as the 80's'll ping with hot temperatures >115F and bad fuel.

 

[LXPearl]

I have used 87 in my 2001 LC in Colo, but not 85. It did not knock on 87. I used 87 in the LC predominantly without knocking, though it got sluggish when traveling fully loaded, so I started using 89 or 91 after that on trips. My LX has been using 91/93 octane regularly. It gets about 15 mpg vs 14.5 mpg for the LC. While the mpg difference may not be significant, the LX torque feels consistently much better than the LC with 87 octane.

I did not try 85 because I also have a late 94 Toyota Previa (supercharged) that recommends 91 octane, but I have run 87 in it for years without knocking. On a trip in Colo, I tried 85 and it did knock some. I have not used 85 in it since then. While the SC may run better at altitude than non-SC, it still struggles more than at sea level on acceleration. On the other hand, I have always obtained about 10% better mpg in the Rockies.

The additives in the gasoline is a different issue. I used non-toptier gas for years in the Previa and last year the check engine light kept coming on. The dealer replaced the EGR valve and gas cap, and it had minimal effect. Next recommended cleaning the exhaust valves and manifold. Instead, I went through a serie of Redline and Techron fuel system treatments over the next couple months, and the CEL finally quit coming on. I have since used only top tier gas in it. No CEL problems.