Hey everyone! I’ve been digging around but can’t find much info about unleaded 88 vs regular 87 octane in a normally aspirated 2.0 engine. Most of what I’ve seen is about EcoBoost engines, but I’m curious about how it affects fuel economy for cars like my 2014 Focus SE with a 5-speed manual.
For those of you who like crunching numbers, have you noticed any difference in mileage between the two? Did you need to go through a ‘transition’ period like with E85? I’m not interested in E85 itself, just these two fuels. Let me know your experiences!
I’ve wondered about this too. Since it’s flex-fuel, the system might be able to adjust to 88 octane (which usually has less ethanol). But I’ve heard the cost savings are minimal compared to the increased efficiency, so I haven’t tested it myself.
Testing would be tricky though. The MPG readout on the Focus is pretty inaccurate, so you’d have to do fill-ups at the same pump, keep driving habits consistent, and run multiple tanks without mixing fuels. It’d take some dedication to get solid results.
@Ash
Good points! I’d love to test it properly, but right now I’m doing seasonal delivery work, so my driving habits and mileage are all over the place. Not ideal for testing.
I’ve got a 2015 Focus SE with the NA 2.0 flex-fuel engine. I’ve used E85 occasionally when I find it, but for regular unleaded (89, 91, or 93 where I’m at), the difference is minor. Didn’t notice much improvement in mileage to justify the price difference.
The 2012 manual says, “Premium fuel will provide improved performance,” so the engine mapping probably adjusts to run slightly leaner, which could help with fuel economy. I’ve noticed a bit more torque on midgrade, but fuel economy improvements weren’t enough to make it worth the extra cost unless you’re after the better performance.
No problem! I also fill up with E85 every three tanks or so. The ethanol burns hotter, which helps keep the catalytic converter and engine deposits clean. Performance-wise, 85 octane actually feels the best out of the three.
I’ve got a 2010 Focus, and here in Pennsylvania, Sheetz sells 88 octane. It’s cheaper, but I noticed worse gas mileage and my car revs higher than normal on the highway when using cruise control.
Unleaded 88 has 15% ethanol, compared to the 10% limit on regular unleaded. Ethanol is 30% less energy-dense than gasoline, so the more ethanol, the lower your fuel economy.
There’s no need for a ‘transition’ period if your car is flex-fuel capable. That’s the whole point—it adjusts automatically to whatever fuel you put in.