I shift based on the air fuel ratio. Once I see it start to drop, thats when I drop a gear.

So depending on conditions(wind, hills, etc) I may run in 6th, 5th or 4th.

This is a 2014 3.5L with 3.73’s and 315/70R17’s. It will pull in 6th with the larger tires without issue.

 

High-octane gas contains less energy per gallon, and doesn't burn as well. You'd get better MPG (in ALL conditions), more hp/torque, and better engine durability using the correct fuel. Running 93 in an engine built for 87/89 doesn't make any more sense than running diesel in it. This page has several old TSBs, but they're still relevant:

(click this text)

 

Ecoboosts can easily take advantage of 93 octane, particularly while towing. They are not even close to MBT spark on 93 at higher loads.

They are not "built" for 87/89, they simply can run on it due to the direct injection and ability for the PCM to remove a lot of ignition timing.

 

Pretty clueless on this topic pal, might be best to move on.

 

You clearly don't understand the topic you're attempting to give advice on.

Running higher octane gasoline than what's *needed* won't destroy your fuel system. It will simply waste a few dollars at the pump. Diesel won't run a gasoline engine and will most certainly reek havoc on your fuel system and result in expensive repairs, including dropping and draining the tank and possibly destroying a fuel pickup/pump.

While lower octane fuel does transfer energy at a different rate in a controlled environment compared to higher octane fuel, higher octane fuel in an engine *optimized* for higher octane fuel (e.g., the EB) is NOT a waste. Also, if you don't understand compression ratios as well as pre-detonation and/or pre-ignition, you should not be giving advice on what octane fuel to run.

Here's a good explanation: Octane is the measure of a gasoline’s ability to resist knocking or pinging during combustion. The higher the octane rating, the greater the fuel’s resistance to knocking or pinging. The knocking or pinging in your engine occurs when the air/fuel mixture detonates prematurely. In broad terms, fuels with a higher octane rating are used in high-performance gas engines that have higher compression ratios.Another way to look at octane is that a lower octane number has a faster burn rate. It has a better ability to expel energy faster. A higher octane fuel slows the wave front of the combustion flame and raises the temperature at which combustion occurs. For example, you may have driven an older car that pings. Even though it has a low-compression engine, carbon buildup on the piston or on the cylinder head can cause a hot spot, which can pre-ignite the fuel, causing a ping. Using a higher-octane fuel can alleviate these symptoms.

 

Don't wanna dogpile on ol Steve, here, but I concur with roadPilot's post, particularly his fourth paragraph.

I've always believed that octane rating is resistance to preignition, a slower burn rate. As such, running a higher octane gasoline should make necessary some additional spark advance otherwise some torque is left laying on the table.

It could be that when towing and using a higher octane in a modern, digitally-managed engine the PCM sees through it's usual sensor inputs (one of which is reading resistance at the spark gap) that it can advance spark timing (even slightly) which very well could result in a slight increase in torque...

 

The post I was replying to doesn't mention Ecoboost.You're clearly talking about something I didn't write. IDK who said something would destroy a fuel system, but it wasn't me. Pay closer attention to your replies....which is essentially saying exactly what the last TSB at that link says, so yes, we ALL already knew all of that info.

 

ACKSCHEWALLY....

While the engines have the ability to retard timing, this is not a new feature and they don't perform magical timing retard not capable by every other motor. How much timing can be advanced / retarded is simply a function of how much range was programmed into the ECU. For any engine, you can program enough retard to run 85, or 83, or 79... but each compression ratio has a point of diminishing returns with timing retard, where combustion is started so late in the cycle that more energy is burned in the exhaust than in the cylinder, and you burn up your cats.

The 'magic' being performed in eco's is the 10:1 compression ratio, VCT, fly-by-wire throttle, and DI.

10:1 is a lower compression ratio by current engine standards, the Honda Fit, as an example, is 10.4 and calls for 87 only.
VCT's and eThrottle let the ECU control the effective CR (how much air gets into the combustion chambers).
Direct Injection lets the ECU dictate WHEN fuel is added, which impacts the speed of the flame advance.

So, technically, these engines ARE built for 87 octane. Part is being able to generate more power at that octane that older engines (combustion chamber design, better cooling, etc), and part is being able to restrict air intake so the engine performs like one of a lower compression ratio.

You don't, you have to have the 8" cluster, and make a change in FORScan to display boost for one of the gauges (so you don't have to dig through the menu to see it).

 

The 3.3L and 5.0's can too. They are a 12:1 compression ratio with direct injection. Again, they are easily capable of utilizing 93 octane but are able to run on 87.

 

Ok, youre arguing about how I worded it.

Sure, they could have a 12:1 compression ratio and not run on 87 at all. The point being that the engine was likely not designed with 87 as the ideal fuel but is simply capable of doing it due to the technology it has. Just like a GM 6.2L(which has a higher CR than the 5.3L) is not meant to run 87 but can.

Honda Fit's don't pull 14,000 lb trailers up davis dam. If you floored a honda fit for more than 15 seconds you are likely going way beyond legal speed limits.