Does all E85 fuel contain 85% ethanol? | Fuel Tips | Articles

The E85 Science: “Straight gasoline doesn’t contain any oxygen and is combusted with oxygen from the atmosphere,” explains Zachary Santner, technical specialist with Sunoco Race Fuels. Ethanol, on the other hand, contains about 34% oxygen by weight. “Using ethanol, E85, as a fuel can increase the power output because more oxygen is available for combustion in the engine,” he continues. “Similar idea to turbocharging or nitrous to add more oxygen to the engine.”

The E85 Advantage: “Ethanol and E85 absorbs more heat than gasoline when it evaporates from liquid to gas phase,” Santner explains. “This cooling effect helps increase performance. E85 can also stand higher compression and boost without detonation when compared to high-octane unleaded fuels.”

The E85 Warning: E85 requires more fuel volume than gasoline–about 30% to 40% more, Santner says. “This means that a gasoline car’s stock fuel system can’t handle the fuel volume and needs to be upgraded,” he explains. Ethanol fuels also absorb water from the atmosphere, so they require airtight storage and fuel systems. Some fuel systems contain plastics and gaskets that can’t handle fuels containing more than 10% ethanol.

The E85 Reality Check: That E85 pump at the corner might not distribute fuel containing exactly 85% ethanol. “Pump E85 has to conform with seasonal vapor pressure regulations,” Santner explains. The U.S. Department of Energy’s website shows the range: “E85 (or flex fuel) is an ethanol-gasoline blend containing 51% to 83% ethanol, depending on geography and season, and qualifies as an alternative fuel under EPAct.” A look at the Safety Data Sheets, typically found online, will back up those swings. “Sunoco E85-R is exactly 85% ethanol and 15% race fuel every time,” Santner continues, explaining that this eliminates the need to constantly retune due to the inconsistencies of the fuel source.

Comments

perrytrice
7/20/21 12:29 p.m.

Towards the roads end!

84FSP UltraDork
7/20/21 7:07 p.m.

Happy that my local pumps are typically 75% E which is pretty nice as I have gotten as low as 55%. The GM/Conti sensor reads real-time ethanol content out on your standard cheap-o obd scanner.

David S. Wallens Editorial Director
7/20/21 7:11 p.m.

Look for some more E85 talk in the October issue. Something I learned while talking with Zach: The gasoline component of E85 can vary, too. So E85 could contain 49% 83-octane or 15% 100-octane.

Keith Tanner GRM+ Memberand MegaDork
7/20/21 7:16 p.m.

This is why you don't really want an E85 tune if you don't have an E85 sensor. You'll get away with most of the time probably but you won't really be able to take full advantage.

Pete. (l33t FS) GRM+ Memberand MegaDork
7/20/21 7:25 p.m.

In reply to Keith Tanner :

Even the OEM sensorless ethanol content detection schemes do not work very well.

malibuguy GRM+ Memberand HalfDork
7/20/21 9:45 p.m.

I put 2gal on top of the 93 in my turbo tercel for a bit of hot weather insurance at the last autoX and was surprised how noticeably quicker the car was on the drive home. Not radical by anymeans...but it was enough to notice it was just "happier" and ran out the upper gears with more gusto then ever before.

jwagner (Forum Supporter) Reader
7/20/21 10:10 p.m.

Keith Tanner said:
This is why you don't really want an E85 tune if you don't have an E85 sensor. You'll get away with most of the time probably but you won't really be able to take full advantage.

Or tune for and buy racing fuel so you get a known ethanol content and the quality of the remaining gas is (supposedly) better too.

pinchvalve (Forum Supporter) GRM+ Memberand MegaDork
7/21/21 7:34 a.m.

E30 tunes are popular with the FiST, but that means mixing E85 with pump gas to achieve 30% Ethanol. Every time you fill up, you have to test the fuel and mix accordingly. The extra power sounds nice, but I don't want to set up a chem lab every time I need gas. I wish the ethanol content was a constant so you could mix easily. Apparently, up to E50 is OK, but over that you don't make more power and you have to upgrade the fuel system.

Opti Dork
7/21/21 8:06 a.m.

I ran E85 on the ND without an E85 sensor. I checked a few local stations and found Murphys and Kroger were generally between 80-90%. After I found a couple that were good I would check them before filling up the first couple times, once I felt safe that they were pretty consistent I only checked them every few months, or when the weather changed. The consensus around me is Kroger and Murphys are always good, but the other places are all over. The local racing group has seen as low as 30 or 40% from other stations.

David S. Wallens Editorial Director
7/21/21 10:14 a.m.

Speaking of E85, any specific questions for our fuel engineer friend at Sunoco?