Gas Octane

I put in 89. In Iowa the 89 is $.10 cheaper than 87 and $.30 cheaper than 91/93. The only down side is 10% ethanol. I've never had any issues with it. I might try out a few tanks of 91/93 and see if i get better gas mileage.

 

i fill up with 87.....run it down to half then fill it with 93 run that down then 87 and so on and so on

 

I use 87 octane. I tried 93 in my 2003 Tundra 4x4 4.7 auto, 2007 Tacoma 2wd 2.7 auto, 2008 Subaru Impreza awd 2.5i auto, and saw no noticeable difference in power or fuel mileage. My 1993 Toyota pickup 4x4 2.4 22re 5 spd did get about 4 mpg more on 93, but I don't know that I noticed any more power. My uncle had the same experience with a similar Toyota pickup (1990's 2.4 22re). I have not tried 93 in my 2011 Tacoma 4x4 2.7 5 spd, but since it's also a 2.7 2TR-FE, I don't see why it would be different from the 2007

I also had 70's vintage Chevy that would knock like a diesel, and drop 4-5 mpg on 87, so I always ran 93 in that...

 

Other than marginally lower MPG, you never will have any problems with it in a Tacoma. Problems are with small engines (lawnmowers, generators, etc.) and older model vehicles that aren't built to handle it.

The interesting thing about ethanol is it effectively raises octane rating of the fuel.

 

I use 91

 

87 most of time. Unless I feel like driving 20 miles round trip to the nearest station that has ethanol free 91 octane

 

There are stations that do not have ethanol. Only certain states require it in all gas. I think it should be in no gas. All it does is increase the price of food, lower your gas mileage, destroy small motors, ruin boat motors, and gives some politician that feeling that they have done something "good for the environment".

 

That is an understatement

 

Maine has had 10% ethanol for years it pisses me off to buy 10 gallons of gas and only get 9 if I want alcohol I'll buy beer but I run the stuff in every thing chain saws, mowers, pumps, generators, etc and have had no problems even over the winter.

 

I've tried 87 and 91 on long drives (6 hours at 65mph) and found that 87 gave me better mileage according to my Sanguage.
Never had a issue with knocking on any of my Toyota's!

 

I run 91

 

I have started using 93 past 2 tanks. Using the buttmeter it is peppier at lower speeds with a modest increase in mileage.

 

this has been beaten and stabbed oh so much...

I understand some of you guys believe that information on the web about how higher octane this and that.... one thing i read on those sites posted is "if the engine is designed for 87"

a couple things, i did some research on toyota engines, the majority if not all are made for 10-15% ethanol and use of 85/87-91/93 octane, from my 72 FJ40 to my 85 supra can handle it.

im the type of guy that doesn't believe this posted on-line too likely, i do my own research. Here in souteast georgia we get 87, 89, and 91 and i have ran 91 since day one/mile one on the odo on my truck and it runs great, i have been doing a on going test since june on my truck running 87 to see if the differance is big, and i feel better running 91, it runs stronger better, smoother overall better in my eyes.... when im done this week ill post numbers if you guys want.

I believe to each there own. Its my truck, my money and if i feel better and believe 91 is overall better in my vehicles then that's what i run...

My 07 4runner limited v6 4x2 gets around ~24mpg (~400mi per tank) running 91 and that's my wife driving it and she doesn't have a light foot.

like i said to each there own... try it and if u see a difference then great if you don't then great too...

it wont cost you too much if much at all if you do a little experimenting of your own.

my 2 cents

good luck guys

 

I was doing a little research myself and found this website about compression ratios http://muller.net/sonny/crx/compression/. The first 2 sentences state, "An engine's compression ratio is a key factor in how the engine will perform. Generally, engines with high compression ratio (10:1 and higher) have less resistance to detonation and require high octane gas."

Also, on http://www.edmunds.com/toyota/tacoma/2011/features-specs.html?sub=double-cab&style=101336174 , scroll down and it says the recommended fuel type is "premium unleaded (recommended)". Very interesting. Looks like I'm going to be switching to premium from now on.

 

For all you scangauge owners it is very easy to check to see if the 93 vs 87 octane really gives you any change in mpg.

I see this when we shift from winter gas to summer, and I see if significant change when I can get ethanol free gas.

With ethanol free I will see tank after tank of fillups with essentially the same fuel adjustment of about 2%. Winter comes along and the fuel adjustment goes up to around 9%. Ethanol summer gas is around 7%. Unfortunately my local station that had been carrying ethanol free stopped carrying it 2 years ago and it's not available anywhere near.

The scangauge essentially expect the gas usage to stay consistent with the gas you've been using, but if the next tank is indeed getting worse mpg due to say using 87 then it will think you used a lot less gas and the next fillup will be way off.

Anyone with a scangauge and V6 want to use this method as a test on the benefit of 91/93? It should eliminate most of the other variables that make comparing tanks difficult.

Though not perfectly accurate i can say that I get approximately 5% better mpg ethanol free vs 10%, and 7% vs winter blend.

I have never run 91 to check but don't expect to with the I4 and no knock sensor. If 91 was ethanol free it could be worth it, but I see 10% for all grades at the pumps.

 

Also thought I'd add that the reason that 95 octane is okay at higher altitude isn't because there is less o2 as had been said but because the atmospheric pressure is much lower.

It is the cylinder pressure that matters, so a compression ratio to octane relationship isn't so cut and dried.

Just throwing out a few numbers but at sea level atmospheric pressure is about 14.7 psi, while at 5430 it's 12. With a 10:1 compression ratio an engine in Boulder will see cylinder pressures around (14.7 - 12) X 10 = 27psi lower or thereabouts.

I would guess those with V6 in the mountains either see some serious ignition timing adjustments or the lower pressure simply maxes out any timing advance and no additional benefit would be seen.

Another one the scangauge guys could check with the IGN display to find how far ignition will advance.

 

IGN I could easily check, I'm running midgrade right now which is 89 in my area, 93 got too expensive again.

So when I set my SGII to show the IGN, what exactly should I be looking for? High numbers if I'm on higher octane gas?

 

Yep. At full throttle you should see whatever the maximum value is. With 87 the knock sensor may kick in sooner and won't allow IGN to advance as far, hence less power. With 89 it could be somewhat higher, and 91, 93 higher yet.

Ultimately if the advance maxes out and the knock sensor doesn't kick in there is no need for higher octane for that situation. If we know say 40 is max and your not hitting that then more octane would help.

Edit - actually you'll see higher ignition advance under light or no throttle, but it's the value at full throttle that matters for power.

 

The owner's manual for my 2010 4.0L V6 Tacoma says nothing about using 91 octane (96 RON) for better performance. It only says to "use unleaded gasoline. (octane rating 87 [Research Octane Number 91] or higher)" in section 1-5. Refueling, on page 75.

So I use 87.

I tried using 91/93 for a month and saw no discenable difference with the IGN readout on my Scangauge. I also felt no noticeable difference in power and saw no real difference in calculated MPG.

So, I'll stick with 87 from now on......... unless I have the TRD supercharger installed.