# Trying E85 for first time - '09 MB C300

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I would not quite agree with that way of determining actual cost. The only way to do it right is to determine cost per mile. My 2015 2500 6.0L flex fuel. I get an average of 14 mpg with it (gravel roads, highway, in town, off road, all of it) on regular. With E85, about 11 mpg average. Now, regular in my area is running around \$2.08 right now. So the cost per mile is roughly 14.8 cents a mile. E85 right now is running \$1.60, which at 11 mpg is roughly 14.5 cents a mile. I have been using E15 for quite a while. The mpg with it is similar to regular, but the fuel is about \$1.99 now, for a cost per mile of around 14.2 cents a mile. Premium is running around \$2.60 in my area now. The mpg is no different than using regular in my ride. So the cost per mile would be 18.5 cents a mile. If I was choosing between E85 and premium, E85 would win in a landslide due to being about 4 cents a mile cheaper to use. Each engine is different and mpg spreads will not be similar. Just basing things on a generic BTU lost percentage or some other generic idea won't give a real picture of cost benefit.

i made the calculations based on the numbers provided. in the original post the comparison was being made on the price of E85 vs the Premium Fuel. In OP: "Using excel I paid 36.5-37.8% less for E85 versus comparable premium at both pumps. At Speedway in Tennessee it was \$1.44/gal for E85 vs \$2.27/gal Premium" the formula is valid, and is how to account for the loss of value of any product, and in this example the posters own example for loss of mileage using the E85 vs the premium leads to paying too much. You will be at the pump a lot sooner buying the lower price fuel but visiting the pump more frequently.

pezzy669: your actual cost to use the E85 based on the loss of mileage you provided is this: \$1.44(what you paid for E85)/.2635(your percentage loss in mileage)=\$5.46 you now compare your actual cost of \$5.46(taking into account mileage loss) vs the \$2.27 price of the premium. this is how you compare apples to apples. if i misunderstood something in your original post, please let me know and I would be glad to refigure the "actual cost of the E85 taking into account the mileage loss so that a better comparison can be made taking into account the energy value loss from using the ethanol.
I left out one small portion in arriving at the actual cost.... and that is the actual yield of the E85 is 100-26.35=73.65%(this is the actual yield of the lower energy value based on the numbers provided. The actual cost in dollars is then 1.44/.7365=\$1.96 This is the number to compare to the \$2.27 My apologies i missed this. So yes, in this instance the E85 is a lower cost even taking into account the loss in mileage.

i made the calculations based on the numbers provided. in the original post the comparison was being made on the price of E85 vs the Premium Fuel. In OP: "Using excel I paid 36.5-37.8% less for E85 versus comparable premium at both pumps. At Speedway in Tennessee it was \$1.44/gal for E85 vs \$2.27/gal Premium" the formula is valid, and is how to account for the loss of value of any product, and in this example the posters own example for loss of mileage using the E85 vs the premium leads to paying too much. You will be at the pump a lot sooner buying the lower price fuel but visiting the pump more frequently.
formula is valid, but i had an error, i have corrected it.

Originally Posted By: TiredTrucker
I would not quite agree with that way of determining actual cost. The only way to do it right is to determine cost per mile. My 2015 2500 6.0L flex fuel. I get an average of 14 mpg with it (gravel roads, highway, in town, off road, all of it) on regular. With E85, about 11 mpg average. Now, regular in my area is running around \$2.08 right now. So the cost per mile is roughly 14.8 cents a mile. E85 right now is running \$1.60, which at 11 mpg is roughly 14.5 cents a mile. I have been using E15 for quite a while. The mpg with it is similar to regular, but the fuel is about \$1.99 now, for a cost per mile of around 14.2 cents a mile. Premium is running around \$2.60 in my area now. The mpg is no different than using regular in my ride. So the cost per mile would be 18.5 cents a mile. If I was choosing between E85 and premium, E85 would win in a landslide due to being about 4 cents a mile cheaper to use. Each engine is different and mpg spreads will not be similar. Just basing things on a generic BTU lost percentage or some other generic idea won't give a real picture of cost benefit.
Using your numbers, i arrive at the following: \$2.08 regular vs \$1.60 E85 Actual yield of E85 based on your mileage loss is 78.6% (14-11=3. 3/14=21.4% 100%-21.4=78.6%) Actual cost of running E85=\$1.60/.786=\$2.03 So your comparison based on actual costs(incorporating loss of energy value) is \$2.03 of E85 to \$2.08 to your available regular as you called it. Hope this helps out and let me know if I can clear anything up on my calculation.

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Well, my numbers are actual on the ground numbers from my pickup. It is all so simple. Cost per gallon divided by number of miles per gallon equal cost per mile. No need to complicate everything. One thing I learned in college from my math profs was to use the simplest formula to get the job done. Everything else is a waste of time.

I hear you Mr. Trucker, different strokes for different folks... I like to look at the "actual" cost taking into account the energy loss, so that when I get to the pump, I can say for example E0=\$2.44 a gallon E10=\$2.32 pump price, but taking into account energy loss my actual cost is \$2.65. Based on my mileage loss(2.32/.875=\$2.65) so it is an easy choice for me to fuel up with the E0 at \$2.44 vs the \$2.65 actual cost from energy loss.

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