Gas prices explained

[GJM120]

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That may have been the case for a very simple refinery. In a more complex refinery some of the naphtha stream is blended into gasoline directly but most goes to a downstream unit (the reformer) and makes pretty high octane blending stock. There is some adjustment that can be made trading off octane for volume. I've already exhausted my recollection of all this so maybe someone else can chime in.

 

[ripcord]

I read an article a couple of years ago that the auto manufacturers are lobbying congress heavily to raise the minimum octane rating to 91+(R+M)/2. At the same time the environmental lobby is pushing hard for reductions in aromatics (like benzine) in gas formulations which would necessitate E30 or E40 to maintain octane ratings.

 

[bbhero]

Originally Posted by 2015_PSD
Originally Posted by Kestas
This makes it all the more curious why manufacturers are moving toward premium burning engines, more so than before. Last I heard, 41% of all new engines manufactured are made for premium. BTW I know the answer is CAFE.
Consider all of the small displacement engines that are turbocharged (single and twin) on the market these days that are making more power than V-8 engines of yesteryear. The move for the vast majority of manufacturer's is towards these type engines to reduce cost and increase power and economy (which is a CAFE item), but at the same time due to the power factors often require (or at least recommend) premium fuel.


Very good point PSD....

High compression ratios closing in on 14:1 is a big part of the actual need for higher octane.

 

[fdcg27]

Originally Posted by bbhero
Very good point PSD....

High compression ratios closing in on 14:1 is a big part of the actual need for higher octane.

Sure, but these same modern engines typically have a lot of valve overlap, so the effective compression ratio is much lower than the calculated one.

 

[bbhero]

Doubt it is a substantial difference....
This why higher octane is actually needed...

 

[Kestas]

In the grand scheme of things, the efficiency of turbos and high compression is a red herring in this discussion. For most of the motoring public, their mission is to get from point A to point B in the cheapest way possible. Do you think they care what is under the hood? Explain how an engine (or better yet, vehicle) is more efficient if it requires more expensive gasoline? I doubt the expense of fuel offsets any engineered "efficiencies" in the engine. You need to step back and look at the bigger picture, and not just the marvels of the engine.

 

[CarbonSteel]

Originally Posted by Kestas
In the grand scheme of things, the efficiency of turbos and high compression is a red herring in this discussion. For most of the motoring public, their mission is to get from point A to point B in the cheapest way possible. Do you think they care what is under the hood? Explain how an engine (or better yet, vehicle) is more efficient if it requires more expensive gasoline? I doubt the expense of fuel offsets any engineered "efficiencies" in the engine. You need to step back and look at the bigger picture, and not just the marvels of the engine.

Color me confused, but you stated that CAFE is the reason for more engines (41%) that require premium fuel, I offered that more turbocharged engines are the reason for the premium fuel requirement so how is that a "red herring"? It would seem they go hand in hand as the root cause for requiring higher octane fuel--else why would you need to run a premium fuel?

It would seem that one would need to compare a non-turbo version versus the turbo version of the same engine (provided that one exists) to obtain the MPG for each and then factor in the cost differential of the fuel. If the turbocharged engine achieves more MPG to the point that it offsets the cost, then it is a win across the board.

Feel free to correct me if I am not understanding your point.

 

[JohnG]

Originally Posted by supton
Then that must mean you're sticking it to the middle class then? I don't think I've ever used premium. I've never owned a vehicle that it would make a difference in--if I could prove that it would lower my cost/mile

No, not really. If you think of all the work and parts and valves and computer control that goes into building a blending rack, you would see it differently. I was thinking 91 octane and done.

Then you get into transportation, pipelining, transmix disposal, storage tanks at the terminal, storage tanks at the station, dispensing pumps. I'm sure that all of those saving (especially in California) would be passed on to ALL consumers.

 

[Kestas]

The reason is that CAFE doesn't care how expensive the fuel is, nor how much the refineries use our natural resources to produce a gallon of gas, so long as a car gets many miles per gallon. Originally CAFE was to help ease the consumption of gasoline. With the increased disparity between the price of octanes, the unintended consequence of CAFE is that now many people spend more money on fuel to get from point A to point B. This works against the public good.

You used the example of a turbocharger, suggesting it may offset the extra cost (+25%) with premium. If true, my argument falls apart. Let me cite the example of using regular in my cars that recommend premium. I save the 25% cost with virtually no loss in MPG. I only lose some acceleration.

 

[4WD]

Originally Posted by Kestas
The reason is that CAFE doesn't care how expensive the fuel is, nor how much the refineries use our natural resources to produce a gallon of gas, so long as a car gets many miles per gallon. Originally CAFE was to help ease the consumption of gasoline. With the increased disparity between the price of octanes, the unintended consequence of CAFE is that now many people spend more money on fuel to get from point A to point B. This works against the public good.

You used the example of a turbocharger, suggesting it may offset the extra cost (+25%) with premium. If true, my argument falls apart. Let me cite the example of using regular in my cars that recommend premium. I save the 25% cost with virtually no loss in MPG. I only lose some acceleration.


And having so many different mandatory blends does not make it so easy to squeeze the most from each barrel …

 

[tbm5690]

Shoppers for the most part look at the MPGs on the window sticker and that's all that matters. I don't agree with it, especially since rarely is it actually cheaper to get a new vehicle for better MPGs vs keeping the current one, premium fuel or not. Yet, they still buy the new one and say "look at the money I'm saving on gas."

 

[Quattro Pete]

Originally Posted by tbm5690
Yet, they still buy the new one and say "look at the money I'm saving on gas."

If one is looking for an excuse to buy a new car, this one is as good as any.

 

[Vern_in_IL]

You must remember, you save more going from 19 to 20 mpg than you do from 40 to 41mpg.