[Trevor McCullough!]

Hey all, about a month or so ago i decided to switch from running 87 octane with 10% ethanol to 91 octane ethanol free. I didn't necessarily expect to see an increase in MPG from the switch, but what I did not expect to see was a loss in MPG. Does anyone know if this is common if there is a reason for the loss? When i first switched I drove a little easier adn picked up roughly 2 MPG, but after about 2 months of running it i am down around .5 or 1 MPG from when i was running 10% ethanol. Again i didn't expect to see a gain just not sure why i would see a loss while still having the same driving habits.
Thanks in advance, Trevor

 

[JohnnyMac]

It might be the change in octane rating. As a general rule, octane doesn't really correlate to energy content. The octane rating pretty much only tells you how much you can compress the gas before it combusts. Also, different gasoline manufacturers increase octane in different ways. In terms of actual energy content, higher octane gas can be lower in energy. You can increase your octane with alcohol, however, alcohol has only about 60 percent of the energy of gasoline. Basically E10.
Engines are designed for a specific octane rating. If you use a higher octane than what your engine specifies you are paying extra for gasoline is designed for higher compression engines or tuned/modified engines. I've advanced my timing with a Bully Dog tuner and so I need to use premium but a stock Titan only needs 87. I'd try to either run 87 for a while and see if there's any change. If you need 91 octane, then and buy it from the same place all the time, try buying from someplace else (I prefer Chevron) and see if that changes anything. Could just be low quality gas with cheap octane boosting. Or your truck may have recently cracked a manifold which will affect your mileage and have nothing to do with the gas..... My two cents....

 

[Trevor McCullough!]

I have no mods currently that require a boost in octane. My reason for switching was more so to get the benefits of running ethanol free... or so what i believe are benefits haha. I will have to try running regular 87 octane and run an ethanol delete and see what that does for me. I had a bullydog in a previous ram but have not purchased one for my titan yet. I believe i just hit roughly 52,000 miles and she's a 2012. I live in western NY so i normally fill up atdelta sonic so that I can wash it everytime i fill up to keep the salt off.

 

[HRTKD]

It's the octane. I did a test of octane when I did a large loop driving through Wyoming. On my truck, 85 octane gave the best MPH while 91 octane gave the worst. 85 octane is the lowest available in this part of country and elevation.

I've also run 91 Ethanol-free fuel and found very little gain in MPG. It might have been .5 MPH gain. Certainly not worth the extra cost of the Ethanol-free fuel.

 

[nightowl]

I always get 1.5-2 mpg increase with non ethanol gas. Its always a given increase with my 05 flex Titan and same with my buddies 2010 Tundra. Very odd you see a decrease.

 

[OneQuick06]

It might be the change in octane rating. As a general rule, octane doesn't really correlate to energy content. The octane rating pretty much only tells you how much you can compress the gas before it combusts. Also, different gasoline manufacturers increase octane in different ways. In terms of actual energy content, higher octane gas can be lower in energy. You can increase your octane with alcohol, however, alcohol has only about 60 percent of the energy of gasoline. Basically E10.
Engines are designed for a specific octane rating. If you use a higher octane than what your engine specifies you are paying extra for gasoline is designed for higher compression engines or tuned/modified engines. I've advanced my timing with a Bully Dog tuner and so I need to use premium but a stock Titan only needs 87. I'd try to either run 87 for a while and see if there's any change. If you need 91 octane, then and buy it from the same place all the time, try buying from someplace else (I prefer Chevron) and see if that changes anything. Could just be low quality gas with cheap octane boosting. Or your truck may have recently cracked a manifold which will affect your mileage and have nothing to do with the gas..... My two cents....

It's the octane. I did a test of octane when I did a large loop driving through Wyoming. On my truck, 85 octane gave the best MPH while 91 octane gave the worst. 85 octane is the lowest available in this part of country and elevation.

I've also run 91 Ethanol-free fuel and found very little gain in MPG. It might have been .5 MPH gain. Certainly not worth the extra cost of the Ethanol-free fuel.

Very good, valid posts. My bet is that if you found 87 ethanol free, you'd gain back your mpgs and maybe a bit more. Back when I first got mine, I experimented with different octanes and none yielded any net gain of sorts. I did find that E10 yielded less mpgs on average (1.5 at most), but not terribly. Now that the non ETOH places charge anywhere from 15 to 30 cents more per gallon, I just stick with 87 E10.

I've also ran a few tanks of E85, and while the truck didn't skip a beat, there was a significant drop in mileage. I could get about 265-270 on a tank of that, instead of the 300-315 I get on E10.

 

[HRTKD]

I always get 1.5-2 mpg increase with non ethanol gas. Its always a given increase with my 05 flex Titan and same with my buddies 2010 Tundra. Very odd you see a decrease.

You being closer to sea level may give you more bang for the buck with Ethanol-free fuel than I'm seeing at 6,000' elevation. I could be wrong, I had fun in chemistry class blowing stuff up, not necessarily learning helpful stuff.

 

[OneQuick06]

You being closer to sea level may give you more bang for the buck with Ethanol-free fuel than I'm seeing at 6,000' elevation. I could be wrong, I had fun in chemistry class blowing stuff up, not necessarily learning helpful stuff.

Haha, we do benefit from denser air being pretty much at sea level.
There's a noticeable swing in power when the temps get into the 50s and lower and the humidity is as low, compared to the hot, humid armpit days.

The T runs hard down here in the Winter.