Mileage vs. Octane (revisited)

[cbecker333]

I went on a long-ass trip (150mi) @ 65mph for the bulk of the drive. I filled her up with 87 octane before the trip...and guess what? I got better mileage than I have ever gotten out of 91 octane fuel...30mpg!! Best I ever got with 91 was more like 26mpg. This might not be the same if I was using hondata's ECU map - I think they optimize it for higher octane.

[mrfixit687]

i got 29 mpg with mostly freeway driving with 91 octane before

[ADAMnQuickCIVIC]

forget mileage, what about longevity...
detonation associated with 87 octane will kill your engine prematurely...
i dont care what honda reccomends, for me it's premium every day...

[i-WERKS]

Why would they recommend that if it causes detonation?
I've filled up 87 a couple of times and had no problems what so ever and I'm sure a lot of other people would tell you the same

[Cone Killer]

Originally posted by i-WERKS
Why would they recommend that if it causes detonation?
I've filled up 87 a couple of times and had no problems what so ever and I'm sure a lot of other people would tell you the same

I doubt it's the octane rating. I have a feeling it was the additives that are put in the gas for the winter. I have numerous dyno runs with 87 octane WITHOUT detonation before winter. When summer rolls around, I'll go back to 87.

[blueiedgod]

I just did a 600 mile round trip. I averaged 25 mpg at 80 MPH with an occasional burst to 100 MPH, and an occasional red-line pick up. I attribute the numbers to new engine as i am at 1200 miles on the odo, winter gas, and wind resistance at 80 MPH. I am sure had i been driving at 60 MPH i would have gotten the EPA estimated 30 mpg, but I simply could not, she just wants to be driven fast. my rule of thumb is: if you are going to speed, go 15 MPH over the limit. I have used the rule for a few years, and have not been pulled over.
take care

p.s. I used regular on the way down and premium on the way up, saw no difference. except in my wallet.

[civic_on_juice]

Go figure this.

I have been averaging 28-34 mpg, combined city/highway. In town my Si gets better mileage with 89 octane than 87 or 91!? 28 or so with 87, and average of 30 with 89. I did notice a big difference in low end power with the higher octanes. My driveway is an uphill right hand turn, with 87 octane the Si would lug in 1st gear, with 89 or 91 octane it pulls no problem.

Try this!! On the highway (I have 17,000 miles since September), 87 or 89 octane, 30-34 mpg. 91 octance 30-32. No difference in driving performance. Not big differences, but there none the less.

For me 89 in town, 87 on the highway.

One more item, in most colder climates the EPA mandates an oxygenated gas (so I have been told). The stuff stinks, really smells bad. Gas mileage drops 1-2 mpg and performance drops.

Hope this helps..............