Using E85 in my 335i (basic stuff to look at)

Looking to start using some e85 in your car but are unsure how to start? Here’s my experience with it. Hopefully it helps clear up some of the confusion I had about it.

I’ve been getting a lot of PM’s on the forums lately asking how I use e85. How much to use? How to calculate? What to look for in logs? I hate to give my unqualified advice without any context.
Here’s my very long winded experience.

I am by no means an expert so take that into consideration when modifying your vehicle.

There was a very informative discussion in the MHD beta group about cylinder timing and how important a role that plays with engine tuning. I feel like this factor is often overlooked on the forums and deserves more attention so here it goes.

Important note: It’s important to establish how/why you’re going to use e85.

In my case, it’s to supplement the terrible fuel quality in California. The “winter blend” CA 91 octane fuel sucks according to my logs and butt dyno, without it I just about always get lots of timing corrections and the car just doesn’t feel as alive as it does with e85.

The quick and dirty (how I started, JB4 map 5):

  1. I started with about 3.5 gallons of E85 and worked my way up to between 3.7-.8 gallons of e85 on every other fill up. I would sometimes go on closer to the low side, sometimes to the high side but I stuck between those amounts.
    • I started using e85 when I was using my JB4 on map 5 w/flex fuel wires…
    • One time I added about 4 gallons and the car did not like it at all, at highway speeds under load at high RPM’s the car stuttered and struggled to make any power. From that point on I only used at max 3.8 gallons. This from what I read on the n54tech forums, was a symptom of to much e85.
    • According to the forums, PWG cars can handle more e85 than their EWG counterparts. No idea why, I’ve just read that, a lot.
    • If you’re into this stuff like I am, I highly suggest you take the time to learn how to read your logs and make sure you’re not using too much.
    • The problem with the F30’s and using e85 across the board is usually the fuel delivery system. Gasoline has more energy than e85, so as a result more e85 mixed fuel is needed for the same explosion. Yes the octane is higher, but so is the fuel consumption.
  2. The difference I felt using e85 vs no e85 was significant, the butt dyno could tell for sure.
  3. In my logs, really the only thing I was looking at, at the time was my WGDC, boost/boost target, AFR, STFT (making sure I’m not maxing out the fueling system) etc… I wasn’t looking at cylinder timing corrections or anything like that.
  4. Every few fill ups (no science to it) I would fill up with just regular 91 octane, as kind of a reset to the tank.
    • My thought here was/is there will always be some e85 left in the gasoline, I’d like to keep it diluted down to a somewhat calculable level, so putting in just a fresh batch of 91 should dilute it down enough for that. Not sure if this did anything but logically it makes sense in my head.
  5. And that’s it, I never had any problems putting in the 3.5-3.8 gallons of e85 with the JB4 (or MHD so far), the car felt and ran great. Being the nerd I am and with a plethora of new logging parameters, I am now doing the below, I think once I get it dialed  in and verified with data I will go back to this method.

How I e85 now (MHD tuned):

  1. Get a baseline
    • Depending on what kind of fuel you have available in your area and depending on the options your tune provides do a few baseline pulls without e85.
    • In your baseline logs on datazap or whatever your preferred log viewer is, take a look at the values next to “Cyl Timing Cor”
    • My baseline run with no e85 in the tank, lots of timing corrections
  2. If those values are 0 or don’t bounce around too much then (like in the below gif):
    • That’s good. It doesn’t paint the whole picture but it can mean your:
      • Tune is tuned well
      • Your fuel quality is good
      • Your plugs/coils are doing fine
      • Same tune, same mods, just with a little e85 in the tank, barely any timing corrections


  3.  If those values jump around a bunch then:
    • Add about 3.5 gallons of e85 which according to the calculator, should give you close to around 93 octane fuel
    • Again take a look at your “Cyl Timing Cor” for all 6 cylinders and see if it’s still pulling timing, if it is across the board, maybe try a different gas station or a little bit more e85
      • If only a cylinder or two is corrected a lot, that could be indicative of a weak coil on that cylinder, weak spark plug, or maybe something else…
  4. Something to be mindful of when adding more e85 is your “Rail Pressure Mean PSI”
    • On your test pull (4th gear WOT in my case) that value should not dip below 1600psi, if it does, that may be an indication you’re using to much e85 (there are other factors but just keep this in mind.)
    • To dumb it down to my level, because I’m not the sharpest knife in the drawer… It takes much more e85 to deliver same energy as gasoline, the injectors have to inject more and your fuel pump can’t keep up with that extra volume being sprayed through all the injectors, as a result your fuel rail pressure crashes.
    • Thanks Joseph from the MHD beta for this info!
    • Pretty cool visual demonstrating more fuel, less PSI, RPM rises, injectors inject more, fuel rail pressure goes down


  • e85 quality/ethanol content will vary, see here:
    • “Like gasoline and diesel fuel, E85 and other ethanol-gasoline blends are adjusted seasonally and geographically to ensure proper starting and performance.”

    • I was able to get in touch with California’s largest E85 distributor, Pearson Fuels and this what the CEO had to say about E85 content/quality in California
      • “That is a great question because the labels that we are required to post on the dispensers by different government agencies can be very confusing. While we do have the ability to vary the blend seasonally, in reality, all the E85 we blend in the entire state is calculated to be blended at 83.3% ethanol. We regularly do field testing and the fuel almost always comes back within 1-2% of 83.3%. This little variance can probably be attributed to variances in the evaporation rates of ethanol and gasoline and the fact that a big tank of thousands of gallons might have some variation throughout the tank, much like you might have an alcoholic drink that can be stronger at the bottom or top.

        The California Air Resources Board allows us to blend at a rate lower than 83.3% but if we did that then the price of E85 would have to go up about $.20 per gallon because we would then be subject to state excise tax which we are exempt from now. It is a conflict between air pollution regulations and tax laws so it should continue to be 83.3% unless we make a big social media announcement one day, which we do not see on the horizon.

        Very rarely, we will have a blend that is not at the 83% (less than 1% of the deliveries). In that case, if it is still legal E85 then we will sell it and put a sign on the pump that says “Attention Racers: This E85 is blended at XX%. This a temporary situation and when this sign is removed it will revert to 83%”. I think that has happened 2-3 times in the history of the company so it is very much the exception. Every once in a while someone will contact us and tell us that the blend percentage is off or we hear chatter on the social media and when we test the fuel almost every time the blend is right near 83%.”
        Mike Lewis, CEO of Pearson Fuels

    • And another response from Pearson Fuels regarding octane content, thanks to Rob in the whatsapp beta chat for the question:
    • Our Octane is about 103 research Octane. Research is expensive to test for (about $1,500) and the enforcement agencies don’t really test for it so people get away with claiming whatever they want to claim. The one time we tested for it, it was 103.1 Research Octane. Most of the time in our brochures we just say it is 100+ Research Octane to account for any variability but most of the time it is very close to 103.

      There is another E85 supplier that likes to claim their E85 is 105 octane, we would love to see someone take a picture of the label on their pump and then call them on it and ask to see the results to prove it is 105. We don’t think it is that high.”

    • California folks, check out Pearson Fuels app on your iPhone or Android, it’s an E85 station finder, I found out my E85 station is a Pearson Fuels station

  • Bookmark this site:
  • Bookmark this thread: N54tech forums, JB4 log reading
  • F30 335i fuel tank size is 15.85 gallons aka 60 litres (source: Here), when I do my calculations I use 15.8 gallons
  • An app to track your fuel usage. I use Drivvo on my android (iphone app as well) to log all my car maintenance and fueling. It’s very intuitive and works well, highly suggest it.

More disclaimer stuff

Everything I write here is from my own personal experience, research from the forums to the interwebz, to lately some very informative Whatsapp discussions in the MHD beta group. I didn’t go to school for this, I don’t work in the industry, I’m just a dude really interested in this stuff. There’s a ton of posts claiming you should never mix e85 and how bad it is for rubber seals, and the engine and the blah blah blah. Do your own research before reading and listening to what some random dude is writing on a blog on the internet.

As always I welcome all constructive feedback in hopes of making this an accurate and informative post, please add to the discussion!

Final thoughts

In my experience, the addition of e85 to my tank has definitely improved my ignition timing. The car pulls harder and runs smoother throughout the rev range. I’m yet to read of anyone doing any harm to their engines by mixing in small amounts.

Much more to come as I learn more, bounce this off people who actually know what they’re talking about, I created a forum post, please come join the discussion here!


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