High Octane Fuel
 

Here in Montreal we have 3 grades of gas: 87, 89 and 91 octane.
I noticed that the pump says that 87 and 89 "may contain up to 10% ethanol" but there is no such label on 91.

While I heard that higher octane might not give a boost in FE, I was wondering, would there be any advantage of driving on 91 (E0) rather than 87 (E10)?

Thursdays, the difference between 87 and 91 is only 11.4 cents/gallon rather than 22.8. Do you think it's worth it? (keeping in mind gas here is about $5.14/gallon)

The only advantage is if your engine is tuned to run on higher octane, or if your engine is experiencing knock due to timing while running a lower rated gas.

Best way to find out is to try it, some people see an increase in mileage when they use pure gasoline and some people don't see a difference.

...99% of the time, use 87-octane per manual; but (1%) will up it to 91 or 93-octane when heavily-loaded and driving in hilly country (Colorado).

E10 has about 3% less energy than gasoline, but your price difference is about 2% so I'd say you could save money by buying premium, if it really is pure gasoline. But I bet it isn't. I bet the increased antiknock rating comes from MTBE, which also has less energy than gasoline, but more than ethanol. So you're probably breaking even.
-mort

Stick with

http://www.adclassix.com/images/66sunoco260gasoline.jpg

My '03 Kia Rio's mileage would dip by about 3% MPG when I used 89 instead of 87. So I stopped using anything other than 87 even if a station sold 87 and 89 octanes for the same price. However, I think all of this was before E10 appeared.

...yeah, I remember the "good old" premium high-test SUNOCO 260, wish it was still available here in Arizona.

And the T-Rex of the American Interstate. The phrase can't outrun a radio had no meaning when the LEO's had these:

http://assets.hemmings.com/story_ima...00-0.jpg?rev=2

Todays supercars might have more top end, but it's meaningless without the open road of yesteryear.

As to todays cars and fuels, mid-grade seems to work well for the additive package (fewer fuel-related problems on small-engined equipment as the test).

.

I have done several 'tests' while taking my trips to Texas from CA.
My car is one of those that says '91'.
It does make a difference in mpg if I drop down. according to the scangauge, the ign advance drops down.
Whoever in othere threads (ignoring the ethonl) going up to 91 from a car that is supposed to run 87 didnt help.

But I think mort might be onto something in his post.

I have always used the octane recommended in my car's manual (87) even if the engine has a rather high Compression Ratio (10.5:1). Modern ECU/ECM can easily manage lower octane with higher compression engines by adjusting the timing accordingly, to a certain extent. I might try 89 (E5) or 91 (E0) octane gas this summer and see if the ECM can advance the timing on its own for increased efficiency.

A while back i put in a tank of 93 instead of 87. Driving on premium is alot more fun! I would that was a noticeable difference.

If you're able to fiddle with valve timing, I'm pretty sure you can use the valve timing to limit power at low rpm and use lower octane gas on a high compression engine, since variable cam phasing systems typically advance the cam to increase power at the expense of greater detonation risk (hence, high octane gas to compensate), and maintain the same spark timing and therefore not lose economy.

I think it varies too much car to car to predict.

"BoB" used to see no difference between 91RON E0 or 91RON E10 and about 6% better FE on 95RON E0 (at 8-10% higher cost).

"Baa" gets better FE on E0 91RON than the other two.
(The recommended fuel for each car is 91RON E0).

I'd suggest you run a few tanks of each and work out cost per mile for your vehicle and driving conditions.

mcrews -

I've been using 91 but I am switching to 87 right now to save $ and to see what happens in the next few tanks.

CarloSW2

Yeah, I marked 91. My car requires premium, and unfortunately, 93 isn't an option in CA.

The Bobsled wants 91, so it gets whatever is available over 89. Sometimes that's 91, sometimes it's 93. My last car, the Flying ****box (96 Esteem sedan), specified 87 but was a little peppier on 91 so it got that sometimes.

I hadn't known that we had censorware here. :rolleyes:

We have 85, 87 and 91 as the standard octanes at 5000 feet altitude.

I use 88 octane pure gas at one of the ma-pa gas stations. The Corvette dealership here also uses that 88 pure gas to fill up their new Corvettes.

I was going to give a big thumbs up to the 89 octane pure gas I got 3 weeks ago. I sold my car two weeks ago and have been riding the bikes exclusively.

The fuel mileage on both bikes went up considerably, but we also have had extremely warm weather here with temps in the 80s last two days, an new record yesterday.

It would be hard to give any exact amount but the increase was in the neighborhood of 10%. I should get my 2011 Fiesta next week, the DMV is dragging their arse again, even though it is costing them hundreds of dollars in taxes.

But then their procrastination has meant I used 10 gallons of gas to cover 733 miles. The weather has been most cooperative.

regards
Mech