High Octane Fuel

[CigaR007]

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.

[sheepdog 44]

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.

[serialk11r]

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.

[D.O.G.]

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.

[cfg83]

mcrews -

Originally Posted by mcrews

...
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'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

[Ladogaboy]

Originally Posted by mcrews

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.

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

[Fat Charlie]

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.

[Fat Charlie]

I hadn't known that we had censorware here.

[99metro]

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.

[user removed]

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