Are there really any differences between various brands of gasoline? My friend insists that Arco gas gets less mpg than Mobil. I say that the gas industry is so highly regulated that all brands are the same. Any straight poo??
S
“Stock” gasoline is produced at manny refineries and is traded and sold amongst the various distributors, as needed. What you buy as Shell gasoline may very well have been refined into gasoline by Chevron and sold to Shell, who will then add whatever chemical goodies they deem important to make Shell gasoline the grooviest. The additives are proprietary and unique to the brand (sort of).
Ultimately, there’s little difference.
Does anyone know if the various additives actually do anything, or are they just fancy marketing gimmicks? What about my friends assertion that Arco gas gets less mpg, which offsets its substantially lower cost (about .10/G)?
Spanks in advance,
SeTh
Arco does less marketing, and thus can afford to sell the gas cheaper. Mobil charges more money to give you the privilage of watching their commercials on TV.
As far as regular 87-octane stuff, gasoline is gasoline. Some of the higher octane detergent laden stuff may be different from brand-to-brand, but most med-sized/mid-priced sedans(i.e. 90% of the U.S. car market) have engines optimized for 87-octane gasoline, and if you look in your owners manual, it often tells you that your car will get the best performance out of the cheap stuff. Some high performance vehicles do get better high-end power out of the high octance stuff, but unless you are driving your Ferrari down the interstate at a buck twenty, your probably best off, economically and performance-wise, driving your Camry down to Bill’s No Name Gas Station and pumping it full of the cheap stuff.
One thing that does change is the type of gas per area. Here in Texas, there are different regulations. If you’re in the Dallas/Ft. Worth area, where I live, we have a cleaner gas, but it costs a little more and the gas mileage is worse. If you drive outside of the county, the gas prices drop about $0.05 - $0.08 and you get more for your money. It’s dirtier, though. Just one more thing to consider when comparing quality of gas. But, in my experience, I haven’t noticed any difference between gases from the same area.
Saeren, don’t forget that you guys in DFW and Houston have to pay for vapor-return equipment at the gas stations. Those of us down in Austin and San Antonio don’t have those requirements (yet) so the gas is a little cheaper.
In my opinion, I am wary of truly hole-in-the-wall gas stations. If the station’s outsides are dirty, what do their tanks look like. I don’t want to put dirty, filthy gas in my car. Even if the fuel-filter catches the debris, it’s still a pain to change it.
I don’t know about practical differences, but there are chemical differences (additives and whatnot).
I have a friend that used to be a chemist for one of the major oil companies. He once testified in a case where the company was being sued by a woman who claimed that their gas damaged her car. By analyzing the gas he was able to show that it wasn’t even their gas that was in the car.
After years of anally writing down my mileage and how much gas I buy, I can say that ARCO gas does give me about 15-20% less mpg than other brands.
One friend told me that it was because ARCO didn’t maintain their tanks as well, and that there was a lot of water in the gas they sold. Dunno if that’s true, but my numbers tell me to never buy ARCO gas unless it’s an emergency.
Do you drive in roughly the same environments tank for tank - I know that my mileage can range from 15-30 mpg depending on the roads I take, if I have the A/C on, etc. Do you know for sure that the gas is the culprit?
Gasolines can vary widely in composition, and even those with the same octane value can be very different. Both in their physical makeup and their molecular structure and constituents. For example, Pennsylvania petroleums are high in normal and branched parrafins, but California and Gulf Coast base stock are high in cycloparrafins.
Some examples of gross heating values of gasolines (unfortunately, in CGS units) in the US:
California - 11,016 cal/gram - 11,690 cal/gram
Kansas - 11,504 cal/gram - 11,871 cal/gram
Oklahoma - 11,707 cal.gram to 11,896 cal.gram
Pennsylvania - 11,424 cal/gram - 12,042 cal/gram
Texas - 11,470 cal/gram to 12,022 cal/gram
If you look at this on a net heating value basis, it’s possible one could see a wider variation if hydrogen content varied considerably.
In this limited and older sampling (note - these are all non-oxygenated gasolines) we see a variation from a low of 11,016 cal/gram to a high of 12,042 cal/gram. Or, relative to the high value, a drop of as much as 1/12 (or about 8.3%), which if you make a bunch of assumptions and simplifications is probably close to a 7-8% difference in mpg.
I have to admit, being an expert on fuels and fuel quality (although NOT gasoline in particular), this seems like a surprisingly large range of heating values for a fuel as tightly regulated as gasoline. So there could be some error here.
I agree with what you say about the differences between fuels from different states, and have no doubt that local/regional clean air laws force oil companies to do stuff to their gas that can affect its’ performance. But within a given market, wouldn’t all of these chemical differences be eliminated?
The afforementioned brand-specific additives and formulations can make a substantial difference in performance. My 1985 Celica GT-S Convertible does not tolerate Texaco 87 or 89 octane fuel very well at all. I get substantial knocking on Texaco fuel unless I spring for the 91 octane grade. However, Phillips and Conoco 87 cause almost no knocking. On the other hand, my father’s 1994 SL300 (which I had the great fortune to borrow for a month while my Celica’s powerplant was being rejuvenated) devoured every brand of 89 octane fuel I tried without complaint. I suspected that carbon buildup was the culprit in my Celica until this behavior continued after a total top-end rebuild. In those days, I was driving a 40+ mile commute each way 5 days a week and had ample opportunity to experiment with different factors like weather, A/C vs. top folded down, spirited driving (which actually reduced knock, btw) light cruising, etc. I also know for a fact that Phillips, Texaco, and Conoco gasoline sold here (Oklahoma) are all distilled in geographically seperated areas and are not in any way the same base product. Phillips refines in Borger TX, Conoco in Ponca City OK, and Texaco somewhere around Houston.
In other words, if your car’s engine is sensitive to certain factors (and I still haven’t figured out why my Toyota is thus inclined), certain brands of fuel may offer better performance than others. The best advice I have is to avoid gas companies that don’t refine their own fuel, stay away from stations that look poorly maintained, and experiment with the options that leaves you. Bumping up a grade can offer some improvement if your car does poorly on 87 or 89 octane fuel but is a waste of money otherwise. Higher-octane fuel combusts at a more stable rate but actually contains less specfic energy.
One further bit of advice. If your state requires that the pumps carry an inspection sticker that shows the measured octane of the fuel, take a closer look at that sticker. I noticed tonight that my neighborhood Conoco station station received a grade of -4 on their 91 octane fuel and 0 on the 87 grade which meant that on the day that the pump was tested, all three grades were identical (89 is almost invariably a 50/50 blend of 87 and 91 mixed at the pump itself these days). I won’t be filling up there again.
sethdallob saideth:
While I don’t know about fancy additives (for example, additives that are both floor wax AND dessert topping), but I can tell you that in California the “gallon” of gasoline actually consists only of about 9/10th of a gallon. The rest comes in the form of an oxygenate called MTBE (Methyl Tertiary Butyl Ether), a generally nasty and known carcinogen that happens to keep your car from emitting as much filth into the air (oops; unfortunately it also pollutes ground water sources and so far nobody’s come up with a way to remove it at the source). I also understand several large cities are now starting to use MTBE-added reformulated gas.
I read in a motorbike mag that petrol (gas to you lot) is sold with a summer and a winter formulation and it does seem that my bike runs smoother all of a sudden in spring, presumably when the summer brew is being sold,than say a couple of days earlier.
just my experience…
While not all gasolines are created equally, I haven’t been able to pick one out that works “better” than the others. I’ve had variou scars that run better on different types of gas. (one was Chevron… one was whatever… the one now is Arco). Don’t ask me why… but I feed the car what it wants, thats all I can say.
Screeme