The U.S. Federal government is mandating E-15, which of course is 15 percent ethanol. Some of you don't need to worry about this and some do.
At EC we are working hard going through the cars and ECU specs year by year to figure out which are E-15 compatible.
As of March 29th, 2026 all EC tunes sent out will be E-15 compatible.
Alfa Romeos,
Giulias and Stelvios 2.0 and 2.9, STOCK:
All years, all versions sold in the United States are E-15 compatible. This is both the official stance from Alfa Romeo and from EC.
Tuned:
Cars with the EC Phase 1 or Phase 2 tunes are fine on E-15. Big turbo cars should avoid E-15 until we do more testing. For now try to use pure gasoline or E-10 until we have more information on this.
4C, The official stance from Alfa Romeo is that these cars are NOT E-15 compatible. Use pure gasoline or E-10 for now.
At EC we have not determined if the 4Cs are OK on E-15, we are testing that so please check back in for updates.
Fiats Stock:
124, All 124s are E-15 compatible. This is true both officially from Fiat and from EC.
500 Abarths, This is complicated:
All 500s have 100 percent E-15 compatible fuel systems but NOT compatible ECUs. It depends on the model year.
2012-2014 ARE NOT E-15 compatible. This is the official stance of Fiat and we at EC agree 100 percent.
2015, Officially from Fiat these are NOT compatible with E-15. However, this appears to be a case of the Fiat owner's manual not keeping up with the ECU parameters. All 2015 Fiat ECUs we checked have absolutely had E-15 compatibility. At EC we think it's likely that all 2015's are E-15 compatible, however it's possible there was a change over date, so we can't say with certainly that they all are. While we do have a lot of ECU software versions on file we can look at, we don't know the build dates of the cars, only the model years.
2016 and up, All are E-15 compatible from both an official Fiat and an EC standpoint.
So what can you do?
If you have a 2012-2014 car, with an EC tune, you may purchase a revision for E-15, or just be sure to used either pure gasoline or E-10. The E-15 revision will work fine with all three fuels should you decide to go that route.
If you have a 2012-2014 car WITHOUT an EC tune, you should try to use only pure gasoline or E-10. Use of E-15 without the proper ECU parameters may cause a check engine light, and will shorten your engine life.
If avoiding E-15 isn't an option you should purchase an EC tune. It you want stock tuning parameters, but ONLY the E-15 update this can be purchased at a reduced price.
If you have 2016 or later Fiat, you don't need to do anything. You already have an E-15 compatible car. This is true for both tuned and stock cars.
2015 is the wild card. We think they are all E-15 compatible, but there may be early build dates which are not. The only way we know is to read the ECU.