[xckeefe12]

Currently driving across the country and seen 85 twice (Nebraska and Colorado) but been too scared to try it. Internet has mixed reviews but it's about $0.15 cheaper per gallon.

Assume either way it has some MPG implications. Anyone use this in the 3.7L, or should I stick to 87.

Thanks

 

[Andre Jones]

Currently driving across the country and seen 85 twice (Nebraska and Colorado) but been too scared to try it. Internet has mixed reviews but it's about $0.15 cheaper per gallon.

Assume either way it has some MPG implications. Anyone use this in the 3.7L, or should I stick to 87.

Thanks

Gross, lol. I bet the 3.7L would run the same but I personally wouldn't test it unless necessary.

 

[mogulman]

Gasoline has about 116K BTUs while ethanol has about 77K BTUs. In general with E85 you will get about a 26% reduction in MPGs.

 

[Adv]

I think he means 85 octane gas which is very different from E85. They have the 85 octane in some of the mountain states out west. The theory is you can get away using lower octane when you are at high elevation. Not everybody agrees with this but you can do your own research. The owners manual calls for a minimum 87 octane so that is what I would use.

 

[Fish]

The knock sensor on the 3.7L will retard the timing to accommodate the low octane fuel, reducing power. So you could run 85 octane gasoline, and at elevation you may or may not notice a difference. Either way, knocking won't be an issue. Likewise, ethanol (E85) has very high octane but lower energy density than gasoline. The 3.7L will advance the timing to accommodate the high octane, and will actually generate more power, even though your fuel economy will be lower.

 

[justcallben]

The 3.7L will advance the timing to accommodate the high octane, and will actually generate more power, even though your fuel economy will be lower.

I'd like to believe that's true but I have tried several episodes of consecutive tanks of 91 vs. 87 and gained nothing, no extra power, no extra MPG, but a deeper hole in my wallet. I refuse to run E85 for too many reasons that I prefer not to discuss so that test will never happen.

 

[brownbear]

No he's talking about E85 I'm sure.

I think it's more for people concerned about the emissions.

 

[Fish]

I'd like to believe that's true but I have tried several episodes of consecutive tanks of 91 vs. 87 and gained nothing, no extra power, no extra MPG, but a deeper hole in my wallet. I refuse to run E85 for too many reasons that I prefer not to discuss so that test will never happen.

The octane difference between 87 and 91 would make a marginal difference in power. And the energy density (which is what affects fuel economy) is not related to octane, so there won't be any additional MPG.

With e85 ethanol, the octane can be as high as 105-110 depending on the seasonal mix. With octane that high, the timing can be advanced significantly, which will result in a measurable (But not necessarily noticeable) increase in power. Ford has published numbers for the 5.0L engine on e85 showing 15 more horsepower and 10 more lbs-ft of torque. I would suspect the 3.7L engine is somewhat less. I would be surprised if anyone could actually noticed those increases, but they are real. But e85 has significantly lower energy density, so the fuel system must flow proportionally more fuel to generate that power. The increase in power does not offset the lower energy density, resulting in lower overall MPG with e85. In most cases, it is not cost effective to run e85.

 

[justcallben]

The octane difference between 87 and 91 would make a marginal difference in power.

Maybe in the Transit but my GMC Savana turned into a rocket when I ran 91 vs 87. But at 11.5 MPG it got expensive real quick.