What brand of gas do you use?

[Jim Ed]

What brand of gas do you use?
I was using non ethanol 91 octane U.S. pump gas Murphy gas at Sam's Club.
Last week end I filled up with non ethanol Alon gas 91 octane U.S. pump gas.
It seems like the Alon gas is a little stronger than the Sam's Club gas.
I have been told it does not need the 91 octane but, it seems like it runs a lot smoother with it.

[foreverska]

I think I usually end up at a chevron buying 91. I'm no gas elitest though.

Non-ethanol gas is a tad stronger. While Ethanol is a higher octane it has a relatively low energy density. That is to say it takes more to make the same power as 91. So that would dillute the energy of the 91. That shouldn't really make a big difference in practice but your butt dyno is your butt dyno.

You do not NEED 91. [NVRMD schooled by marc]

[Marc]

...The timing on these cars were setup to run 91...

That's 91 RON (Research Octane Number).
The octane number posted at the pump in the USA and several other countries is the "(R+M)/2" figure, the numerical average of the fuel's RON and MON (Motor Octane Number). It's also known as the Anti-knock Index (AKI) number.
Why? When the government got involved in price-fixing of fuel, the oil companies reacted with the reasonable-enough-sounding question of what octane number they should post on the pump. After all, it wouldn't do any good to stabilize the price if the quality of the product could remain a variable, right?
In truth, at the time every gas pump in the nation was posted with the RON number, just like those in Europe. After all, it's the higher of the two numbers and makes the product look better. The MON existed, but was never used at point of sale.
Our illustrious Congress bought the argument hook line and sinker that folks could be confused by the two numbers, and agreed to the oil company proposal that their average be used.
The REAL reason for the change was that the oil companies recognized the opportunity to increase their profits even as the government was trying to limit them. Deflated numbers posted on the pump would encourage people to buy more expensive gas than they needed.
This all happened forty-odd years ago and to this day people remain uninformed on the subject and continue to look for fuel with an (R+M)/2 number that's as high as the RON of yore. Since the MON is at least 8 points lower than the RON for most gasolines, this means they're buying fuel that's about 4 points higher than they need...for example, today's 87 AKI gas compares to 91 RON (although it's true that when ethanol is used to raise the octane rather than compounds like tetraetheyl lead the fuel will contain less energy per gallon, the octane is approximately the same); if you buy 91 AKI you're getting fuel that would've been called Premium in the `60s - definitely not what the VW engineers designed for.

Well played, oil companies....well played.

http://en.wikipedia.org/wiki/Octane_rating

[foreverska]

Huh, I did always think it odd that the ultra economy vehical was built to run premium.

[aussiebug]

Well said Marc (as usual).

The RON octane number is still used in the "rest of the world" (outside the USA).

91 RON (the common octane number quoted for 1500/1600 aircooled VW engines) is approximately 87AKI in the USA.

How you get that octane number is not important in itself - the NUMBER is the important thing. Using a too-low number will eventually hurt the engine, but using a too-high number will do nothing for the engine - it will just empty your pocket faster.

This can be confusing when considering ethanol gasolines, because ethanol does have a high octane number so adding it to a low octane fuel can lift the number up to a higher figure. But the real problem with alcohol is that it contains almost 40% of USED oxygen, meaning that there is less "fuel" in the fuel. So having 10% ethanol (called E10 in many countries), results in the fuel having about 4% less energy. This is not a problem for modern cars with Engine Control Units (engine computers) - they can adjust the mixture on the run and you won 't notice any difference in driving performance (just a slight increase in fuel consumption). But the VW engine has fixed jets in the carb, so the engine runs 4% lean, and aircooled VW engines don't like running lean. The only fix is to change the jetting in the carb to get he mixture back into balance.

So if you can, use non-ethanol fuels in your bug.

If you have to use ethanol fuels, you should consider increasing the main jet in the carb to compensate. For info, each increase in main jet size (for example 125 to 127.5, or 130 to 132.5) increases the fuel flow by about 2%. So for E10, you would need a main jet two sizes larger (4% increase in fuel flow). That's usually the only jet which needs changing, but if your carb has a smallish idle jet (smaller than the most common size - 55), then that might need increasing to at least a 55.

[champagne superbeetle]

My '09 Eos's manual suggests gas listed by TopTierGas.com. Shell was (and still is) on that list plus I get breaks from Shell and participating grocery companies. I see more brands have made the list since I last checked, and I will use any of these brands in a pinch.

[aussiebug]

Champagne,

OK, but is the actual fuel you are using sufficiently high octane (91 RON/81 AKI), and does it contain any ethanol? THAT's the critical question - not whether the fuel company tells you it's TopTier or whatever. Those promos might mean something where you live but this forum is world-wide. Each country has its own fuel descriptions so its usually better to stick to the technical description rather than an "advertising" description, if that's what TopTier is.

Rob
Rob and Dave's Aircooled VW pages
Www.vw-resource.com

[Bugzie]

The octane rating may be the same but the fuels (leaded) that were available when our Bugs first hit the road are not the same fuels that are available now. Right?

[aussiebug]

The octane rating may be the same but the fuels (leaded) that were available when our Bugs first hit the road are not the same fuels that are available now. Right?

That's true Bugzie - fuel formulations are always changing, even winter to summer.

Gasoline is a mixture of many different hydrocarbons, plus a few other useful compounds.

In general, fuels these days are formulated to reduce the amount of Benzine compounds, as these are the more environmentally damaging (and carcinogenic) compounds. But unfortunately, they are also the hydrocarbons with the best natural octane ratings, so the trick is to design a fuel with less of the "bad" stuff but still having the required octane rating. That's part of the reason for adding Ethanol to gasoline these days - it has a very high octane number (about 120 from memory), so it improves the octane number for any fuel it's added to. It also mixes OK with gasoline, and helps make for a cleaner burn.

The good thing is that the bug engine is not too fussy about fuels, so long as the octane rating is appropriate. But as I've said above, they don't like oxygenated fuels (Ethanol) because these have a lower energy content, and carburetted cars like the bug cannot adjust on-the-run for the lower energy content, like modern ECU equipped cars can. So if you have to use oxygenated fuels and the engine misbehaves, it's likely that an increase in the size of the main jet (and maybe the idle jet too - see my posts above) will improve the engine's performance back to normal.

[Ol'fogasaurus]

Shell, at least around here, runs about 10-cents or more a gallon higher (although I've seen it over 30 cents higher at times). I remember it from back in the '50d, '60s and '70's when it was pretty bad stuff... too many additives. Every time I got stuck running it (watch your fuel gauge guys) I had to either blow-out the carb (that meant a 130 mph run up then back down a certain hill) then run either some white/3rd pump (top octane) Chevron or if I could find it, some "Flying A" 104/106 octane good stuff (Sunoco was not available where I lived) until the engine started to run right again or do a carb cleanout. I think I read that Shell (out of Europe) now owns both Castrol and Pennzoil.

About the time of the conversion to the different ratings I was told that American was already selling the new stuff and I was told it was "white gas"; true statement or not I tried several tanks of it in my '62 Chev Impala 327/4-spd but didn't notice that much, if any, difference. I still had to re-tune that blasted engine every 2000 to 4000 miles or sooner which after 25 Chevs drove me (pun intended) to another manufactures/competitor's cars.

Some giggles FWIIW on a sleepy morning

Lee

[Jim Ed]

I prefer the U.S. 91 octane pump gas as compared to the 87 U.S. pump gas as preferred by aussiebug. My Type I engine runs smoother when using the U.S. 91 octane pump gas. I guess it is possible that Australian gas is stronger though.

[aussiebug]

Jim,

Don't know if it's "stonger" and I'm not even sure what that means in terms of gasoline (petrol where I live). Our fuel must be clearly marked, so at most servos (gas stations), you get a choice of 91RON unleaded, 95RON premium unleaded, 98 or 100 Ultra unleaded, and 94 E10 (10% Ethanol). Add to that, most servos also sell diesel (lots of diesel cars in Aus) and at-the-pump LPgas (propane/butane) (lots of Aussie cars run on this too). A few servos also have E85 which I think it about 95RON.

91 and 95 Unleaded are straight hydrocarbons.

98 or 100 Ultra unleaded is a straight hydrocarbon but usually is denser too - has more energy per litre so modern cars with engine computers can lean off a little and go further on a tank full...but it's pricey.

94 E10 is just that - 94RON containing 10% ethanol, and is usually about 2-3 cents a litre cheaper than 91 unleaded, but since it contains less energy than straight hydrocarbons, you might go fewer km on a tankfull (they say it burns better so that is supposed to make it get about the same economy). My wife's Honda Jazz runs on either 91 unleaded or 94 E10, and there is no discernible difference in performance or range. Old carburetted cars like the bug don't run well on it unless you increase the jet sizes in the carb to suit.

Diesel is a popular fuel here, you can buy diesel versions of most European cars (VW, Mercs, Volvos, Audis etc) and most pickup trucks and 4WDs (SUVs) from Ford, GM, Isuzu, Mazda, Great Wall, VW and so on have a diesel version as well as petrol. Diesel SHOULD be cheaper than petrol, since there is less refining needed to make it, but it's not - it's always a few cents more than 91 unleaded. When you ask the oil companies why, they say (in winter) "it's the summer driving season in Europe and the US, so there's high demand there..." and in our summer they say "it's used as heating fuel in winter in the US and Europe, so there's more demand there..." Go figure.

LPGas (propane/butane) has been popular here since the 70s since we had/have major "light crude" oil wells off the coast of Victoria, which contains a lot of LPGas. LPGas is a very good road fuel - it's octane number is about 120, it burns super clean so your oil stays clear, it goes into the engine "dry" so does not dilute the oil film on cylinder walls (less wear), and it's about 1/2 the price of petrol (though the oil companies are sneaking the price up). It's popular as either dedicated LPG or as Dual Fuel, where you have both a petrol and an LPGas tank, so you can switch to petrol in remoter areas where LPGas might not be available. You can buy LPGas only versions of locally produced cars, or get just about any petrol engined car converted to dual fuel with the addition of an LPGas tank, evaporator and plumbing to the inlet manifold - cost of conversion is about $2000-3000 depending on the vehicle and the size of LPGas tank. LPGas burns a fraction slower than petrol, so ideally the ignition needs advancing about 4-5 degrees, and also ideally the compression ratio should be increased to take advantage of the higher octane number, but in a dual fuel setup, nothing is done with the compression, and the spark is advanced only about 2 degrees so it will still run OK on petrol. Taxis running LPGas only get around a million km without touching the engine, because it runs so clean.

Then there is also diesel/LPGas combos. This system is any diesel engine which replaces about 25% of the diesel fuel with LPGas - running on both fuels at the same time. Since diesel fuel does not completely combust (black smoke out the exhaust - the technical reason for this is too long to explain here), adding a small percentage of LPGas (or you can use hydrogen or natural gas too) into the air stream, works like a catalyst, so you get almost all the diesel burnt. Its a win win win...better fuel economy out of the diesel fuel and also out of replacing some of the diesel with the cheaper LPGas, more power (some trucks running this system have to limit the amount of LPGas so they don't over-torque the drive shaft), a clean exhaust, and also very clean oil.