So come this spring i'm going to be maxing out the JB+, but the only thing is say i take me car down to 30 miles left on my tank. so i put 4 gallons of e85 and 9.5 gallons of 93. Now do i have to take it down to almost empty every single time? or is there a trick i'm not thinking of that at 1/4 tank i could fill up. or at 1/4 of a tank there is roughly 3.3 gallons left in the tank. so i could do 3 gallons of e85 and then 7 gallons of 93. but all these numbers are rounded and i'm wondering if long term of rounding and rounding and rounding will throw the mixture off eventually and 1/4 of a tank is very vague with the candy corn gas gauge we have. Any tips or tricks?

 

Sounds like a real hassle. Why are you doing this? Are you tracking the car?

 

I don't think it will be a hastle once i get a method down. I want to push the limits of the N18. I might only run it at 80% as I still have to daily the car. BUt i figure why not? if i can safely run the car, monitor my knock and have fun doing it then i don't see a down side.

 

You can use the secret hidden menu function to get an exact reading of the amount of fuel in the tank.

If you don't know how to access the menu search on this forum. Once in menu 6 gives you fuel readings. From memory the first gives you L and R tanks in litres, second gives you the total tank buffered reading in litres.

At least this way you know exactly how much you currently have in the tank, rather than relying on the guage.

However, it doesn't really matter how much is in the tank, as long as you put in a 30/70 mix of new fuel when you add it.

The best way is really to aim for around 20%, that way if you make a slight mistake and get 15% or 25% it is not going to cause problems

 

I would just make a quick table with the ratios for you, and record as you go. For example, if you have 3 carrots left, then plan on about 11 gallons of mix. 2 carrots might mean 12.5 gallons. If you don't worry about topping off the tank, then it will work out for you.

Would you rather have less alcohol or more if you were going to make an error? If you would rather have less, then start with the 93 and have the max amount of E85 you can put in. If the tank fills up before the E85 max quantity is in the tank, then you have less alcohol in the mix. Write down how much you are short, and adjust your table for the next fillup.

If you stop the E85 at the right quantity, then your ratio is right. You still have some capacity in your tank, but that is OK as long as the ratio is correct.

Have fun,
Mike

 

Simple way to calculate it is 2 to 1. It gives you a 35% actual mix which includes the 10% in regular gas so...
3 gal E85 + 6 gal 93 = 9 gal of 97 octane
using 91 octane give you 9 gal roughly 96 octane, 95.7 to be exact.

Total tank capacity is 13.2 gal plus 1.3 reserve. The reserve is what you have left when the DTE in the center cluster reads --- or as I like to refer to it the "You want to walk light?"

Most times I gas up with about 2 carrots left with 4 gal E85 and 8 gal 93. Then once in a while I run it close to reserve and fill with 3 gal E85 and top it with 93. Drops the percentage to 27% and prevents blend creep.

I've had no issues with this blend. Currently running my JB+ at max and Tigger is as happy as a clam.