What octane are u running ?

The lower power rating wasn't to do with the fuel. BOTH engines got de-rated. The 2.7 went from 164 to 159. The power rating was reduced because the ISO spec for measuring power changed a bit.

 

All I can think of is the Family Guy episode where Peter decides to become a redneck and tries to fill his pickup with jet fuel so it will fly.

 

Did I just read this right? You think the engine shuts off going down hills when in gear? I just about spit my coffee out

 

Maybe I can clarify, the injectors stop flowing completely when coasting in gear as opposed to the injectors opening to keep the truck idling while coasting in neutral.

 

And I love how this has turned from "premium gas doesn't do anything at all" to "it's not worth the money" or "mine runs just fine on 87". The timing advances when on higher octane fuel which makes it run better. But use whatever fuel you like as long as it's at least 87. /thread

 

Troof

 

A while back there was a dude on here who had the algorithms for fuel consumption and why we get what we get using math and physics. I'd like to get this guys take on it.

I still maintain that the same amount of power is in the gas, whether 87 or 93 and that octane only increases the pressure under which the fuel will begin to self combust.

There have to be people smarter than me who can be objective and help clarify some of these issues.

1. Is the pressure in the cylinder enough to "predetonate" the gas at 87? (I'm doubtful since that's what toyota recommends)

2. How does elevation factor in? Is 87 enough at sea level?

3. Regarding stores power, assuming I'm right and it is the same amount regardless of octane content, than is it even possible to return higher mileage as some have claimed?

I sincerely believe it does nothing except waste money, but I am also genuinely interested in these questions and the answers to them with facts and logic as opposed to hearsay and "feelings" about what higher octane does

 

I think this would be an interesting experiment: those of you who believe premium fuel will give better performance, MPG, whatever in a vehicle that specifies regular fuel, (or you're just curious to know,) have someone other than yourself fill your tank, and not tell you what grade they put in. Then you drive the vehicle normally, and take notes about how you felt it performed. Also note mileage, but use actual calculation, not the vehicles' displayed value, ie. miles driven divided by gallons of gas used. Do this for at least a couple thousand miles, with the person filling the tank sometimes putting in regular and other times premium, keeping a log of which was used.

Then, compare your driving impressions and fuel mileage calculations to the grade of fuel used each time. Is there a real correlation?

 

You are simply wrong. Our trucks do NOT turn off on descents while in gear. Coasting down hills the engine uses rpm's to control your decent (by default). Even when you disable the feature it still does it to some degree (especially when you don't tap the brakes). When you put it in neutral it releases the engaged engine form the higher rpms. It is observed objectively by watching the RPMs and can also be observed by coasting down a sizable hill in gear versus in neutral. The RPMs will go up in gear and the it won't speed up as quickly as in Neutral.


Also, In my real world test that was recently performed over the last month, I already spelled out the details in ht last couple pages in this thread... I experienced better gas mileage, and a $1 - $1.50 savings per tank with 91/93 versus 89 octane (not 87). Now I line in upstate NY ni an area where the average is well about the national average. SO the difference in saving is probly more for me than the majority. But it still is a very significant difference in performance.

Whether you choose to believe me, or whether you do your own testing or not is up to you. I couldn't care less what octane you use. It's not necessary per the owner's manual, but based on my findings I would recommend using premium.

That said, on smaller less graded hills, it's better to leave it in gear, as the injectors are shut off while coasting using no gas. In addition, I don't recommend everyone go out and start shifting into Neutral on hills. If you don't know when to shift back into drive, you can do damage to your transmission.

The other methods I used to achieve the 22 MPG, was drafting behind larger trucks, Semi's giving you some real savings.

 

If the engine doesn’t have the compression/rpm to necessitate the higher knock sensitivity or higher specific gravity of the fuel you are using, you are giving up power. Higher octane fuel does not “ make more power”. Higher horsepower engines require higher octane fuels because of factors such as compression, rpm, prolonged load etc. You actually want to run the minimum octane required to achieve the most power and most complete burn. Running too much octane can actually damage an engine due to the extreme EGR temps because of un-burned fuel. There are exceptions to this rule. Methanol/Alcohol and oxygenated fuels specifically. If any of you have access to a hydrometer, I encourage you to go pull fuel samples with ratings between 87-93 from the pump and test their specific gravity in the same temperature/environment. I assure you that the numbers will surprise you.

 

This! More is not better in this case.

To the guy still claiming to "save money" using 93, please please read this: https://www.tacomaworld.com/threads/what-octane-are-u-running.580489/page-8#post-19314201

You'd have to get 4 mpg better than I do (conservative estimate) using 87 to even break even. This is simply not possible. Idk where you're math went wrong but i suggest rechecking it.

 

Also taking your truck out of gear downhills is very bad for the transmission for the same reason you cant tow 4x4s on a dolly, dont do it.

 

Look up DFCO, it is a fuel cut off when coasting in gear.

 

I'm saving 2 MPG from 89 to 91/93. I have never run on 87. But I assume i'd pick up another 1MPG savings. My math was based on 91/93 being on average 30 cents more per gallon where I live. If I went by 87 octane, it would be closer to 50 cents per gallon difference.

So basically that would be the same result... if I was comparing to 87, I'd probly need to get 4 MPG better from 87 to 91/03. I think it would be a stretch to get that, but it could be close. I think I would come up 1 MPG short. My results are pretty close to right in line with what you just reported.

And I'm not just claiming. I did it.

If someone thinks I'm here to try to force people into taking my word for it just to puff myself up... I think my post rate pretty much indicates I'm in no way here to try to deceive all of you into believing me. If you can't handle the results I got, forget it. No need to try to angle your response like I'm making it up.

TRUTH

 

Only if you shift back into gear at an undesirably high RPM. No danger or damage when shifting back at low RPMs. They are going to support not doing it to prevent people from doing damage to their transmissions, as they should.

AND...

It does NOT shut the engine off. It closes the injectors. But that is only for coasting at reasonably level conditions. NOT when coasting down steep hills. In that scenario, it has to open back up to allow the rpms to keep the engine at speed and provides some downhill descent control.

 

I'm not going to dig through 11 pages of comments but I hope someone mentioned that the octane you run also depends greatly on the altitude you are driving in. Here in Utah 85 is regular where at lower altitude states 87 is regular. That's because at 4500 feet there is less oxygen and therefore makes ignition due to compression (knocking/pinging) less probable. It's the same effect as higher octane fuel. What really grinds my gears is that I pay the same for 85 as others do for 87 yet the cost to refine the gas is less. Us at higher altitudes should have cheaper gas.

 

Octane rating does not change an engines Brake Specific Fuel Consumption unless it was at a previous deficit.

 

Ignition as well.
Despite still turning, in that mode, it is entirely OFF.

 

Also known as OFF.

It may NOT do it on level surfaces. It DOES do it on steep hills. You can FEEL it when it happens, and if you monitor the fuel flow or MPG, you can see very easily that fuel flow goes to zero and MPG goes to INFINITY.

 

Engine speed is IRRELEVANT if the engine is OFF.

No. It is observed by monitoring the FUEL FLOW.