From Google:
Sunoco is the only major gasoline retailer to sell four grades of gasoline in the United States:
•Regular (87 octane)
•Plus (89 octane)
•Premium (91 octane)
•Ultra®93.
Was it 5 grades long ago?
Wesw,you could re jet those carbs to good effect ,a lady I used to work for has a store that vends supreme grade and she charges over a dollar more a gallon for it and she charges 10 cents more a gal to use your credit card for E 10. (Man this keyboard is killing me this evening )
Gasoline straight from the refiner has an octane rating of about 70. It has to be enhanced with iso-octane or a another chemical that raises to octane level to prevent knocking. 87 octane gasoline requires 13.3% more iso-octane than 85 octane. 91 octane requires 40% more.
Iso-octane is a reference fuel, a yardstick against which gasoline is compared to. It has an antiknock rating of exactly 100 by definition.
The other reference fuel is n-heptane, it has an antiknock rating of zero by definition.
When gasoline has an anti-knock rating of 87, it means it has the same antiknock rating of a fuel that is 87% iso-octane and 13% n-heptane.
There are likely cheaper and more practical fuels to blend with gasoline to raise its antiknock rating including ethanol, butane, toluene, and the recently outlawed tetra-ethyl-lead along with methyl-tertiary-butyl-ether.
Ethanol is the big octane enhancer these days.
Even though pure ethanol only has about a 100 octane rating, in small amounts, such as 10%, it raises the octane rating of the gas as if it had a 119 octane rating. This 119 octane rating is called ethanol’s “blending octane value”.
Sometimes the total is greater than the sum of it’s parts. Blending small amounts of ethanol to gasoline is one such case.
I paid $1.47 today minus a 4 cent per gallon discount. Cost $10 to fill the tank. I heard on the radio briefly though that the wholesale price of gas just went up 50%. So we’ll see what happens. The party might be over.
Gas is in the 1.20s in my 'hood. It’s great to fill the car up for 14 bucks or whatever but it’s sure slamming the oil and gas economy around here.
I agree with texases; keep the gas around a steady 2.50 and avoid the turmoil of up and down.
My oil and gas royalty checks have taken a nasty hit the past year though. They’re a third of what they were the year before. It’s a double-edged sword… 
Its called synergy ,happens occasionally on the road to Serendip -but there is no reason to over do it ,@BLE good point .
Another reason for the price gap is that 87 regular is the price on the sign, the leader to get you to stop at that store and hopefully you’ll buy a few high profit impulse items, cigarettes, sodas, chips etc.
However, now that every place lets you pay at the pump, they need another leader to make you come into the store. Restrooms! Before the pay-at-the-pump era, you couldn’t take restrooms for granted self service gas stops.
kmccune: I have never seen a Sunoco around here but they seem to be everywhere else in the U.S… When my buddy and I got into the service station business in 1976 our first 2 stations were former Hancocks they still had the blend pumps. Many customers had their own special blend that they purchased every time.
@“B.L.E”, do you agree that there are octane enhancers in premium gasoline, and that they cost more than not adding them at all?
Yes, sure, it’s more expensive to make premium, but there is also profit margin. Just like Toyota makes a lot more profit on a Tundra than on a Yaris.
The big jump in price from regular to the next higher grade could very likely be largely to the regular being a loss or a near loss leader.
It’s like when you go to the fast food burger joint and order only the burger. The burger joint made very little or may even have lost money on you. But everybody orders a drink and fries with that burger and suddenly the tab balloons up to nearly ten bucks. The fries and drinks are the burger joint’s profit.
Mid grade is almost always a bad deal, 1/3 the octane boost for 1/2 the price.
You’d be better off filling your tank 1/3 with premium and then topping it up with regular.
Costco sells only Regular and Premium.
Did 50/50 to create 87 octane specified for the Expedition.
If they are selling lower than 87 octane gas, you live in an area where cars don’t need 87 octane because of your elevation above sea level.
Engines that need 87 octane at sea level do just fine with 86 or even 85 when you are a mile above sea level.
Yes, at 5000+ feet AMSL many people say 85 octane may be used in place of 87.
I believe they sell 85 and 89.
But Ford Manual says not to use 85 octane.
But Ford Manual says not to use 85 octane.
Probably says not to use it at sea level. Only place I’ve ever seen 85 octane was in Colorado.
85 is standard for Regular gas in lots of the Rocky Mountain areas. There’s much less oxygen at 3500 ft than there is at sea level, so octane requirements are lower as well. You’ll be fine with the 85 octane.
@“B.L.E”, I think we are pretty much on the same page. We just expressed it a little differently.