Use of mid range gas to get better mpg

[Argyle]

Bob, is there a situation you don't have a graph for? I salute your efforts to help us all out.

[bwilson4web]

Originally Posted by Argyle

Bob, is there a situation you don't have a graph for? . . .

Bob Wilson

[drbrr]

Why does the manual (p. 560) say to use 88 octane or higher, then go on to suggest anything lower may cause pinging problems? If I'm understanding you all correctly, 87 is the way to go, yet clearly that is below the manufacturer's recommendation. Thoughts?

[HTMLSpinnr]

Originally Posted by drbrr

Why does the manual (p. 560) say to use 88 octane or higher, then go on to suggest anything lower may cause pinging problems? If I'm understanding you all correctly, 87 is the way to go, yet clearly that is below the manufacturer's recommendation. Thoughts?

The owner's manual has been revised since then - 87 octane is correct. Do a search for "88 Octane" in the main 2010 Forum - there's a nice long thread about it.

[bwilson4web]

Originally Posted by drbrr

Why does the manual (p. 560) say to use 88 octane or higher, then go on to suggest anything lower may cause pinging problems? If I'm understanding you all correctly, 87 is the way to go, yet clearly that is below the manufacturer's recommendation. Thoughts?

My fuel studies with the 1.6L engine suggested that at very high power levels (aka., high speed, hill climbs,) a higher octane fuel will let the engine tune itself to achieve nearly the same efficiency as E87. I'm seeing a similar effect between the E89 the dealer put in the tank and E87 in my most recent hill climb data.

If I had regular, high-speed commutes in mountainous states like West Virginia or western North Carolina, I would consider running a higher test gasoline. However, I would want to do a couple of tanks both ways and see what happens.

Bob Wilson

[RadioZero]

Bob, i appreciate the suggestion to use 89 or better while mountain climbing. we have a trip scheduled to western NC in a couple of weeks. i be running 89 for the trip. since its summer time (higher temps) would you suggest premium (91/93) over 89?

[qbee42]

With mountain driving, if you are talking about high altitude, the required octane goes down. In many western areas standard octane is 85. Lower air density calls for lower octane.

Tom

[bwilson4web]

Originally Posted by RadioZero

Bob, i appreciate the suggestion to use 89 or better while mountain climbing. we have a trip scheduled to western NC in a couple of weeks. i be running 89 for the trip. since its summer time (higher temps) would you suggest premium (91/93) over 89?

I don't have any 91/93 data that shows the engine tunes to use it. Understand there are narrow power bands, primarily going up a grade at high speed and needing to accelerate that the higher octane can help. This is a very small percentage of ordinary mountain driving ... important sometimes but still pretty small.

I'll still run 87 octane and 'I follow trucks' by letting them set the climbing pace. It has more to do with 'me be cheap' versus being in a car with impatient people who are anxious to find the next bathroom. <wink>

Also, I have long wanted to get some 85 octane gas for my studies. Sad to say, we're only around 700 ft. so 87 is the lowest we get.

Bob Wilson

[RadioZero]

fair enough, thanks to both for the replies.

[drbrr]

The owner's manual has been revised since then - 87 octane is correct. Do a search for "88 Octane" in the main 2010 Forum - there's a nice long thread about it. __________________
If the owner's manual has been revised since then, why is it in the new cars? I just got mine last week and must have the "older" manual. Strange. How does one keep abreast of all the changes?