This is a story about my own experience and experiments with ethanol-free (E0) gas vs ethanol-blend (E10) pump gas. If you plan to make any performance modifications to your EFI-equipped motorcycle you may be interested in what I have learned.


  1. If you have a late-model (post 2000) OEM-stock bike and don’t plan to ever modify it then this may not interest you. My bike ran “ok” – not great but ok – for some years on readily available pump gas (87-octane E10) but it did clog the injectors regularly and eventually got terrible mpg. It idled rough, took a long time to warm up, blubbered a bit, was hard to start when warm, etc. But it ran. Over the years I used a variety of fuel treatments that claim to solve ethanol problems. I could not tell that they made much difference.
  2. While miles-per-gallon using ethanol pump gas is less (my personal experience is 15%-20% less) than non-ethanol (E0), the E0 is difficult to find and quite a bit more expensive. There is no way the mpg gains alone are worth the (often substantial) cost difference.
  3. I’m not opposed to alternative fuels. They’re fine. CNG, ethanol, biodiesel, electricity, whatever. I’m all for them when used in vehicles appropriately designed for them.
  4. The following is in no way a commentary on a dealer or Moto Guzzi. If there is fault to be assigned it is with Congress and the EPA.
  5. The story below is a personal experience. I am neither a scientist nor a lawyer. Your mileage may vary.

A few facts and links to additional reading

  • Ethanol has less energy than gasoline. Approximately 30% less. This is why there is an mpg difference.
  • Ethanol corrodes aluminum and has deleterious effects on many rubber and plastic compounds. Industry requires distribution pumps using stainless steel and nickel-plated metals as well as upgraded rubber components and seals.
  • Ethanol is hydrophilic (easily mixable with water) and hygroscopic (readily absorbs water from the air.) and
  • Ethanol has some upward effect on Octane rating when blended with gasoline. It is somewhat unclear if this is a real or “phantom” effect.
  • Single-hose gas pumps have a “last purchaser” residual of at least .2 gals (a little less than a quart) of whatever the previous customer bought.


  • Bike: 2005 Moto Guzzi Breva 750ie, OEM-stock with addition of Mistral mufflers
  • Mileage: 32,000
  • Condition: Mechanically sound. Just completed professional service at 31k. Fuel/air filter new, injectors R&R’d for ultrasonic cleaning and testing, valve adjust, new plugs, throttle bodies balanced, TPS reset, ECU checked for current OEM fuel map, etc. All systems operating at OEM spec.


I do all my own maintenance so my bike had not been to a dealer since its 12k service in ’07. This year, at 30k+ miles, I decided it was time for a professional to go over it. As part of that I had them install a pair of Mistral mufflers.

The story to date

I picked the bike up and went for a test ride. The bike still had the 87-Octane E10 fuel that I rode in with. It started fine, sounded good. But on the test ride it popped and backfired badly on deceleration.

I discussed it with the dealer and the hope was the ECU would adapt to the new pipes over time and the issue would gradually go away.

I rode the bike approximately 250 miles home. I filled up a couple of times with standard E10 87-Octane pump gas. Over the next few days I rode an additional ~200 miles.

The problem did not go away. The bike popped and backfired on deceleration like an old Harley or some badly-tuned beater of a dirt track car at the local 1/4-mile oval. It was awful. And embarrassing.

I had a Fat Duc O2 modifier. I had been using it prior to the dealer visit. It helped a little with hard starting and such, maybe, but not much. The dealer removed it (appropriately) during service and did not reinstall. So the bike was 100% stock except for the mufflers.

I reinstalled the Fat Duc, starting with the minimum setting. I tried a couple of adjustments, going up a bit each time, to see if it got better. No effect or maybe worse.

Then I removed the Fat Duc and, using VDST software, cleared the DTC codes in the ECU and checked the TPS was still at the proper setting. So the bike was, again, 100% stock except for the mufflers.

Next I went to a nearby town and acquired some 93-Octane non-ethanol E0 gas. I added approximately 3.5 gals to my fuel tank. Ran through that, put in the remainder – about 1.5 gals. And the other day I realized the popping and backfiring were gone. I’d forgotten about it because it wasn’t there anymore. If not totally gone, I’d say it was reduced by 98%+. Just from getting decent fuel.

This occurred over about 250 miles of riding.

Then I ran out of E0 – low fuel light came on – and I thought, “Hmm. What if this is just an octane thing? Maybe it’s not the ethanol. Maybe I should just try the ‘Premium’ pump gas and see what happens.”

I’ve tried that before, but I thought I should try it again and pay more attention. There’s a station right next to my shop that still has dedicated-hose pumps. That is, pumps with a separate hose for each grade of fuel – 87-octane, 89-octane, 93-octane (so no “last purchaser” residue). All E10. It’s a Valero station and Valero sells only ethanol-adulterated fuel. They have their own dedicated ethanol plants scattered across the Midwest and Dakotas.

I filled up with Valero E10 93-octane – approximately 3.5gls. The tank holds about 4.5 gals so that’s about an 80%/20% mix of E10/E0 with both fuels having a nominal Motor Octane rating of 93.

Immediately (within six miles), the popping and backfiring returned. Not quite as bad as with the 87-octane E10 swill I normally use, but definitely there, noticeable and consistent. Also bogging on take-off returned. Harder starting returned. Blubbering returned.

On Sunday I rode about 190 miles to Jefferson, TX and back. Each time I needed fuel I bought 93-Octane “Premium”. It was from single-hose blender pumps because that is what 99% of service stations have now.

All the irritating performance issues are back. The bike pops and bangs on decel. It surges at constant RPM. Actually, it’s not a surge as much as it is a flat spot or momentary drop-off in power output.

I’m on my third tank of 93-Octane E10, in a bike that is mechanically sound and operating at mfg specifications with a single performance modification – less restrictive mufflers.


The bike isn’t the problem, per se. The fuel is. When combined with the added maintenance issues – clogged injectors, clogged fuel filters, swollen and rotted gaskets and o-rings – it makes no sense to keep running ethanol-adulterated fuel if I can help it.

To be fair, with proper equipment and software a new fuel/air map could be loaded into the ECU which would probably compensate for some of the issues. PC Commanders and ECU reflashes, as well as replacement ECUs, are also options.

I may do one of these things, but the point here is that the fuel makes a big difference and what we are getting out of the pump today is not good. Nothing that makes a properly tuned motorcycle, with a relatively common and minor performance enhancement, run like an old tractor should be considered satisfactory.

And if I do choose to invest several hundred dollars into performance enhancements for the EFI system do I really want to clog it up with poor-grade, adulterated fuel?

Over the next few weeks I will be returning to 93-Octane E0 fuel. It is inconvenient to acquire and relatively expensive ($4.20/gl vs. $2.50/gl). I will repeat phase I of this experiment, just to validate that good fuel does, indeed clear up the problems. I need to burn what’s in the tank now, but that probably won’t take too long.

When I’m finished I will post an update.

One thought on “I Have Gas – ethanol vs. ethanol-free performance effects

  1. I concur and agree with your conclusions. I have drag raced car and noticed a ET drop .using E10 fuel vs non alcohol fuels. I also noticed fuel mileage differences between the two fuels in both motorcycle and automobile. Where I now live I have no option. I do however add a fuel system additive by Amsoil about every 1k miles and haven’t experienced any injector problem in 55,000 miles on a 2004 Breva 750, 52,000 miles on a 2007 Breva 1100 or 34,000 miles on my 2014 Cali 1400. Both Brevas had Mistrial exhaust.

Comments are closed.