4-Bangers and octane

It will clean your wallet. Thats about it.

 

I run 87. It ignites better. You are right in saying that higher octane gas takes more energy to ignite. And YES, some "supremes" contain more cleaning ingredients. mid-grade is usually a direct mixture of 87 and 92 (low and high). Octane is not in gasoline. Octane is a gas that burns terribly-that's why we compare our fuel's igniting capability to it.

If you use higher octane gas in a low compression engine, you are not getting the most out of your engine, however it is okay to do so. It can increase emissions and strain on the cat. Low octane gas in high compression engines can detonate if the care is not tuned properly. This is rare.

 

I did not know this, and throughout this entire thread... this final explanation was the easiest to understand.

I am now going to use 87 from here on. Maybe 89 every now and then.

 

Don't waste your money for 89 or higher octane. The computer in the 2.7 engine will not use the additional octane to produce a single additional horsepower. The computer in the 4.0 does make timing adjustments and gets more power with premium fuel.

 

This quote is total crap. Higher octane is only necessary depending on compression ratio. All fuel at all stations is the same. Different retailers add their crap to it. Hell add nitrogen to it, Shell does. Higher octane raises the flash point of fuel. That is it. Compression causes pressure, pressure causes heat, heat causes detonation. If the octane is to low it predetinates. Higher octane in lower compression engines is inefficient as it does not burn completely . Fuel and energy is wasted.

 

I may have to recheck but doesn't a 4.0 call for 87 octane?

Edit;
Checked manual. 87 octane is recommended. no need or no gain for 91. Nissan is the only vehicle that I have ever seen that recommends 91 and says you can run 87. 91 for better performance. The only thing that I never liked was as soon as you run 87 and it detonates it sets off a knock sensor then retards the timing. Pretty much goes off when ever you are under a load. You would never notice but seems like a nasty fix. This only means that it does detonate then retards the timing. Not good for pistons edges or valves.

 

Your getting it confused with the pedestrian 4.0 V12 engine you have in your truck. The 4.0 V6 uses 120 octane racing fuel and makes 389 horsepower. Just ask any X-Runner owner.

 

My stuff is set up to run on straight pure grain alcohol. But is hard to find in our dry counties down here sometimes. I keep a stash handy in an oak barrel outback!

 

good rule of thumb. 9.9:1 compression and less use 87, 9.9-10.5:1 compression use 89, and 10.5-12:1 use 91

edit: the 2.7 is 9.6:1 the v6 10.0:1

 

Up to a certain point with any engine, the more advanced the ignition timing means you get a more complete burn. If you're getting a slight timing pull due to random or intermittent predetonation, then you're making less power and getting worse gas mileage in the long run. The engine was certainly designed to run 87, but not all environmental conditions or gasoline qualities can be taken into account. With efficiency comes less tolerance for outside variables. Running a slightly higher octane (say 89) just helps to ensure that the ECM isn't pulling the timing on a long term basis and that the engine runs within it's optimal efficiency range. Any higher than 89 and you're likely wasting money because the engine can't take advantage of it.

Edit: I may be wrong about all of this. My owner's manual does say that higher octane MAY provide performance benefits, but it's a 2006. There's apparently been a lot of changes to the manual since then (i.e. oil weight requirements). Perhaps a better subject is top tier fuels. I don't know.

 

your are such a nice guy...

One of the best things about our trucks is that they can run on lower quality and or lower octane fuels better then most. People who have experiences with Pemex fuel understand what I am talking about...

 

You can't run 93 octane on the 2.7 unless you have a yellow type R sticker on your truck. Then you will get horse POWER.

 

Hey PSJ, it's called PEE-Mex for a reason. My Dad used to drive from San Diego to Tijuana and buy 60 gallons at a time (two tanks on his van, 36 and 25 gals). Sure he saved some money in the beginning, but after about 8 years it choked to death on carbon and just quit on him. He had to pull the heads and do a valve job and have a bunch of other shit done to it. "Never again" he said. I guess the Tacomas burn that super cheap stuff a little better than a 79 Dodge 360cid V8.

 

Although I am new here, I have run into this with a past vehicle. As it aged, I thought I was helping it by moving up to mid grade and later to high octane. When the prices went up, I tried to move back to low octane and it started pinging. It had actually become reliant on the 91 octane and sounded like crap with the cheaper 87.

 

Put whatever your owner's manual calls for. That's what it was engineered to run on. Only run higher octane if you notice any pinging/knocking (ie, pre-detonation). Otherwise it's generally a waste of money.

http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

 

x2 to jjbeenken. Octane is not a power booster. That is not even it's function. People who claim that do not understand what octane is or why it's used. See the link I posted above from the Federal Trade Commission about octane. Pretty much explains it. Lots of bad information out there that people just repeat over and over.

 

I guess a lot of members didn't get an owners manual or didn't bother to read it. Otherwise why do we get these same threads over and over and over?

 

I would never fill up with Mex Fuel unless I had to! And, most american
V-8's hated the fuel back then, especially the octane levels. I would fill up with american fuel prior to crossing the boarder, with extra fuel on board. I would mix mex fuel with our fuel until it was gone, then fuel additives were your only choice from that point out. I found with the bigger motors, octane boosters help them along back then, but the 4 bangers ran well except for steep inclines which the low octane fuel occasionally made the motor ping under loads. Overall, the Toyotas I drove back then did very well in Baja and ran well on the fuel available in Mex back in the day. I am sure they are designed to run well with low octane fuels. I bet around the world were Toyotas go fuel sources are simular if not worse then baja so thats why they do so well IMO...

 

I use c-16 so

 

I have read, and always though that high octane gas was primarily for higher performance, high compression engines, and in regular engines, like the 2.7, it won't make any difference. My previous car was a Subaru WRX, which was super only, and with the price of gas, being able to now run 87 in my 2.7 5 lug has been really nice. I am getting around 30 MPG using the cheap stuff.