HkCaGu

I recently did a family road trip approximately LAX-(I40)-ABQ-(I25)-DEN-(I70/I15)-LAX. The gas price websites (combined with hotel wifi) were very helpful in planning where to and where not to get gas (and how much to get).

Despite living in a mountainous state, this trip was also the first time I learned about gasoline with Octane ratings below 87. As we entered NM, I began to notice the 86 and 85 being sold at gas stations. It took me little efforts online to find out why--driving in high altitudes do not require that much octane.

So on the way back, at Cedar City, UT (5800 ft), we mixed in a few gallons of 91 to the tank of 85 (purchased in CO) so we'll be ready to drop 3k ft down to 2700 ft (St. George, UT) in only 50 miles, and also leave a spare gallon to get to Las Vegas, NV (cheap gas).

Then the surprise: They do sell 85 at St. George!

I didn't remember seeing any <87 gas sold in AZ's high altitudes, I guess because you can easily drive down to sea level without refueling, and so I thought it ought to be the same from St. George, only 400 miles away from L.A. and even less distance to Needles, CA (600 ft).

So who decides what is allowed at gas pumps?

mecabq

That's interesting. I discovered 86 in Albuquerque, and just assumed it was because that's a less affluent area and fewer octanes costs less money. Thanks for the information.

YVR Cockroach

At the 6,000' ASL evel, air density is about 20% less than at sea level hence combustion chamber pressures are that much lower (unless you have a turbocharger or super charger to compensate). Required octane level are much lower as a result. High octane petrol also doesn't evaporate as well so you may get worse fuel consumption with high octane especially if the air and engine temperatures are cold.

I used to live in Tahoe at about the 6,600' level. If I had high octane (for up there) gas in my old carburetted truck (required it as it was running nearly 11:1 compression) on cold mornings, I had to prime the carb, let the gas evaporate for about 10-20 seconds, then crank the starter otherwise the gas wouldn't evaporate and the engine wouldn't start.

fairviewroad

Wow. Hate to say it, but this makes you sound really, really old.

DLFan2

That has to be one of the most ridiculous statements ever posted at FT.

HereAndThereSC

Not so ridiculous as it may seem.

In Upstate NY, I frequently saw 85/86 octane gas that was targeted specifically for older vehicles with lower compression. (think carbureted). The idea was that less affluent people had older cars, and didn't/wouldn't spend the extra $ on 87 or higher octane as it wasn't needed.

JP

flyingcat2k

YVR is correct. The entire reason that gasoline is sold at lower octanes has more to do with elevation than anything else. The gasoline pool(s) established by local refiners are specifically established at a certain octane level. Refiners would rather keep the octane as low as possible as it allows them to make other feedstocks or hold high octane products in reserve to ship to other markets or for when they run a less agreeable crude slate to make gasoline. Refiners try not to put gasoline into the pool that has a higher octane value than required as it is a higher value product.

The Northeast is different from other areas of the country due to having large populations at sea level and significant populations above 2000' elevation. This allows more pools to be created that gas stations may purchase from without increased transportation costs due to the storage locations being closer than in other areas of the country. Of course, lower octane gasolines cost less but I would be more concerned about the gas station owner charging market price for 87 Octane and actually selling 85. Yes, this is illegal but only if he/she does not change the sticker on the pump to the 85 octane.

As to performance in an automobile, YVR is correct again. Basically, unless your vehicle stipulates the use of high octane fuels, buy the cheap stuff provided that the station owner is reputable. There were station owners that were selling PERC, or dry cleaning fluid, blended in their gasoline. As this is a chlorinated benzene molecule, this is bad news all around. Engines ceaze or throw rods, corrosion everywhere and who knows what a catalytic converter will put out. Chlorinated benzenes are not supposed to be in gasoline so either the gas station owner is selling PERC blends or the refinery has a major quality control issue.

YVR Cockroach

FWIW, the gas in some places is all the same, with the differences in what additives are added as branding. All the fuel sold in Reno (and I guess "northern" Nevada including Tahoe) is sent from the Bay area via pipeline (presumably along I-80).

Souped up GMC truck with a 383 (0.30" overbored 350 c.i. Chevy V-8 with a crank from a 400 c.i. motor). Not to be fooled with! Not too many people passing me on I-80 between Auburn and the Donner Summit. I had to manually set the advance down to 3 degrees ASL if I wanted to start the engine!

Anyway, sad to say so many people are take in by branded gasoline and its performance claims, as well as buying higher octane fuel, when their vehicles don't need it (I know my partner''s 93 Suzuki truck needs at least 89 octane on a dry high-pressure/warm day while my souped-up '86 'vette should need at least 89 - 94 on a really warm day).

mecabq

Whoa, there. Does higher octane not provide higher performance? Does higher octane not cost more? Does Albuquerque not have, on average, more "low performance" autos than California, as well as a vastly lower per-capita income? I didn't know that lower octane was more appropriate at higher altitudes, but it seems from the informed posters in this thread that my assumption that less expensive, lower-octane fuel is appropriate for the New Mexico market (for reasons beyond elevation) had some merit.

flyingcat2k

The dirty little secret of "Big Oil's" marketing campaign is getting out but more and more people just ignore it. Unless you've tweaked the engine or have the high performance vehicles that state it, don't buy the expensive stuff.

YVR - I tip my hat and give you a Tim Allen grunt. I used to work for a specialty chemical company that was trying to get a major retailer to sell an upgraded diesel. The upgrade was our additive package that had to be added in the semi tanker. Much to our chagrin, their marketing didn't feel that it was necessary but that was when diesel was 50 cents cheaper than gasoline. I'm not sure that we would still be selling our additives now that diesel is 50 cents more than gasoline. I'm assuming that the branding additives would likely have to be added at the bulk loading terminal or at the gas station prior to delivery. There is much discussion about this at API finished fuels meetings but it doesn't appear that there is any consensus on additives being worth the money or not.

YVR Cockroach

Not unless the engine requires the higher octane. Higher octane is there to stop uncontrolled combustion (i.e., ones initiated by the spark plug). Higher octane = higher performance is one of the great myths. Higher octane often times does not equate higher energy content of the fuel. Higher octane because you need higher octane gasoline due to a higher (dynamic/static) compression ratio isn't a myth.

ABQ is at 1,600m (5,200') ASL. The mean altitude for NM is 1,740m (5,700') according to Encarta. CA's is 880m (2,700') according to the same source and I would wager the bulk of Californians live within 200' of SL. Combustion chamber pressure in engines in NM are as a result is much lower than in most of CA. You'll find low octane fuels sold in California along the Sierras, and on the eastern side of the range.

Not really. But keep on digging. Colorado has similarly low octane fuels.
If you want to dig yourself out, this link may be a useful read: http://en.wikipedia.org/wiki/Octane_rating. There's on part, which I am not too sure if I buy, that states a car running optimally with 93 octane ASL will run optimally with 91 octane at 1,000' ASL.

FWIW, my current car (or what my GF uses as her daily driver) powered by a fuel-injected version of this is sensitive to ambient temperature, humidity (a difference whether it's raining or just muggy), and atmospheric pressure. And the beast is computer controlled to boot. GM recommends 92 octane for the engine (or rather the successor but mine and the current are pretty identical) but I rarely put more than 89 (bulk of driving is between 0 and 150' ASL) unless it's a hot day and I intend to drive on long climbs.

DenverBrian

Yep, that's us - poor, destitute, poverty-stricken Colorado!

I've had a running argument with one friend for years over octane. He constantly puts "mid grade" into his tank and I constantly remind him that he could just as easily throw the 10 cents a gallon down the drain - it doesn't do anything for his "performance." It apparently does something for his ego.

New cars are so thoroughly computer controlled that you could probably use 84 or 83 octane gas and STILL not get knocking.

YVR Cockroach

To be fair, you could get suboptimal (peak) performance and even reduced mileage as a result but I'd imagine the increase fuel consumption may be more than offset by reduced fuel cost. I just wish all cars were like the Jaguar Mark I XJs which had dual fuel tanks that one could select with a switch. High octane gas for climbs and low octane for slow cruising on the highway and other low HP/load driving!