87 vs 91

Hey everyone, this is my first aside from my introduction. I have a quick question. When researching 2nd gen tacomas, this biggest complaint i found was that the 05 and 06 models with V6 run on premium gas, and the performance suffers greatly if you use the cheap stuff. I just recently bought an 07 and was told it was ok to use the cheap stuff. I have filled her up with 87 and 91 to see if i could tell a difference. I was wondering if anyone had any feedback on the subject. Also, there is a loss of about 10hp and 15ft/tq from 06 to 07, is this explained by the ability to run on cheaper fuel? Any feedback would be appreciated. Thanks

 

You can use what ever gas you like I started with 93 b/c it was cheap when I first got my truck (only two months ago), but now that gas prices are going back up I switched to 87 and haven't noticed any diff. Oddly enough my MPG actually went up 1MPG. As for the lower HP rating there is a thread you should check out...

http://www.tacomaworld.com/forum/technical-chat/966-different-horsepower-ratings-05-06-tacos.html

 

My wife's Lexus RX300 operators manual also says to use Premium fuel. We've been using Regular for about 94,000 miles now.

 

My mom's maxima is supposed to have premium according to the owners manual as well. They ran 87 in it for over 80,000 miles. Then they had a problem with a computer component that affects the timing. They were told they had the problem because they ran a low octane fuel and the car had to compensate for it for too long a period, and that it would normally be okay to run 87 every now and then. It's just the car was designed to use premium. Anyway it was not a dealer and there was no warranty by that time, so my folks felt there was no reason the mechanic would have to shift blame. I plan on driving my truck for a long long time, so I run the premium as the book suggests.

Compression usually has a deciding factor of what you should run, does anyone know what our compression is?

 

on the I4 is 9.6:1
the 4.0L V6 is 10:1

I utilized 91 and higher on my 05 prerunner from the beginning then tried 87 when prices were high and did noticed a slight pinging noise on hard acceleration or steep climbs..so I just stick with 91>

High octane fuel has more potential energy but needs higher heat created by a higher compression engine to properly condition the fuel to release that higher potential energy

from what i have read before on engines with compression ratios of 9.0 : 1 or less you can use unleaded 87 octane fuel. Engines with higher compression ratios usually require higher octane fuels.

when fuel octane is too low for a given compression ratio, the fuel ignites prematurely, too early, and the fuel charge explodes instead of burning thus resulting in an incomplete combustion. so the engine tends to lose power and may cause engine damage. When you hear that knock or pinging, or even detonation, which may vary from a faint noise on light acceleration to a constant, deep hammering noise while driving at a constant speed. bad timing adjustments, vacuum leaks, or excessively lean fuel mixtures can too cause detonation...

 

Bump

 

Feeling bored? Trying to start something today?

 

Evil

 

I pretty much strictly run 87. The 91 here is ethanol free. Ethanol has more energy in it, so I get more horse power as well as better mpg.

 

Never heard of ANYONE getting better mileage with ethanol. have you ever actually tested your theory? because ive seen the opposite MANY times.. its technically considered a higher octane rating, but it takes more of it to reach that, or something.. Not sure. But, You don't get more horsepower out of it.. You can "get" more horsepower out of e85, because it burns cooler, therefore allowing you to add boost, or compression, and increase timing without adverse effects, but mileage GREATLY suffers. Ethanol really isn't good for anything, and I run ethanol free in EVERYTHING, because Ive seen 2-3 mpg better using it. Oh, and don't ever run ethanol in lawn mowers or ATVs or anything that sits unused for any amount of time. It will ruin it

 

Drag racers run ethanol, and my butt dyno says the truck has more power.

 

that being said, I usually run 91 in mine.. because its ethanol free. I recently ran some 93, and mileage seems to have dropped. Which makes sense, the higher the octane rating, the more resistant it is to explosion.. or, the less volatile.. Therefore it doesn't burn well if it doesn't have enough heat and ignition. It also has a lower stoich ratio, which means it runs richer to reach optimum A/F ratio

 

I explained why racers run E85. But they aren't concerned about mileage either.

 

If it works for you then great, because you can get it everywhere. Some states actually have laws against selling ethanol free. But I do my best not to run it

 

I also like the idea of burning less petroleum because it's better for the environment to burn ethanol than petroleum.

 

Pure gas burns around 14.7 stoich A/F. E10 burns around 14-14.1. It burns richer, therefore requiring more fuel to the same amout of air.. Sometimes a little more fuel can create a little more power. But at the sacrifice of efficiency. E85 burns around 9.7 stoich. So it burns really rich

 

Just waiting for someone to link that YouTube video of the guy explaining why higher octane really doesn't make much difference. Blah blah blah. It pops up at every one of these discussions...

Ever since purchase in '14, there was only one time I added regular. I noticed some extra sounds when I accelerated and every now and then during idle.

Went right back to 91 after that and the small noises went away.

No change in MPG, but I wasn't looking for MPG in the first place.

 

That's good info.

It would be interesting to hear what experience others are having too.