Premium or Regular Gas

[SpyderGirl]

Originally Posted by Banzai

Agreed on the first point. Most engines are built with the range of gasoline octane ratings in mind, but using anything higher than recommended MAY improve performance in some cases, but definately WILL lighten your wallet in a very unnecessary manner. Around here, regular gas is $2.43 right now. High test is going for $2.95. Maybe only 5 gallons at a time, or 27 (my truck), so it adds up quick for NO statistical gain in either performance or gas mileage for the average car in America. Perhaps in the mind of the consumer, though.....and SOME cars, such as the Corvette, mandate high test due to their high (for the street) compression ratios. Our engine in the 250 has a compression ratio of only 11.6:1, which is rather mild in the realm of street bike engines.

From Wiki: "Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power."

Thus, since energy density is essentially the same, why pay more money for higher octane rating than is required for a given application? Plain and simple, it's a waste of money. Since our owner's manual states 87 octane (admittedly as a minimum), anything higher without valid reason caused by mechanical alteration of the engine or other environmental requirements is unnecessary.

You remember correctly about aluminum. Aluminum was used during WW2 in many aircraft engines, where octane boosters were pionered (and incidently, lead is STILL used as an octane booster in some aviation fuels). MANY, MANY performance and race cars of the ,late 40s-70s used more and aluminum with leaded fuels, and eventually in the 80s aluminum became common place on production cars. Lead never hurt the aluminum of those motors. If it did, they would not have used either the lead or the aluminum. I, too, learned early on that the lead helped with the lubricity of the valve seats, but I've never seen it in print, although I have seen references to the requirement to install hardened valve seats.

Some of us are old enough to remember when you had to choose the LEADED pump or the UNLEADED at the gas station, and pull up to the proper pump. The unleaded has a smaller nozzle, the leaded a larger. Unleaded only cars are supposed to have a smaller filler restriction so that the leaded nozzle won't fit. In the early days, you could remove the sheet metal restricter with a screwdriver, and many did because unleaded regular was more expensive than leaded high test for many years until unleaded became the national standard. Those who did run the leaded gas in their early unleaded only cars paid a heavy price in repair bills as unleaded was initially championed by localities that also poinered (and still use) the tail pipe smog tests!

Very good info. And in response to the comment regarding using higher octane fuel because of "less additives"... premium fuel contains approximately 92% isooctane ("anti-knock") additive and regular contains approximately 85%.

Also a ratio of up to about 14.7:1 can use regular instead of premium... 11.6:1 is on the leaner side so no issues running 87 and certainly no benefits to running 92.

Happy riding!!

[Alex]

Originally Posted by SpyderGirl

Very good info. And in response to the comment regarding using higher octane fuel because of "less additives"... premium fuel contains approximately 92% isooctane ("anti-knock") additive and regular contains approximately 85%.

Nope. Isoctane is not an additive, it is a molecule that is inherent in automobile gasoline. It is the reference molecule used to set the base level for 100 RON. Heptane is the reference molecule for 0 RON. All major oil companies have reference blends that have certain percentages of these molecules that are used to determine what level of octane can be expected from the fuel that they are currently producing or testing. For more detail on this, just google ASTM D2699 and ASTM D2700, which are the ASTM tests that determine the ending octane rating.

The additive packages that Banzai was talking about are the tiny amounts of detergent, cleaning agents, and preservatives that are added to the commodity gasoline.

Originally Posted by SpyderGirl

Also a ratio of up to about 14.7:1 can use regular instead of premium... 11.6:1 is on the leaner side so no issues running 87 and certainly no benefits to running 92.

This really isn't a good rule of thumb anymore either. There are 12:1 engines that would immediately self-destruct on 87 and require 91, and there are 15:1 engines that will happily run on 87 all day long. The reason for this is that the static compression ratio is only a matter of how much volume is left in the cylinder from top dead center to bottom dead center. What it doesn't take into account is the valve timing that goes along with this. Think of an extreme case, where the valves stay completely open full-time. As the piston comes up, while the static compression ratio would be determined to be compressing, the charge in the cylinder is actually not being compressed at all as long as the valves are open. The extra pressure escapes. So an engine with a high static compression ratio but with alot of valve overlap and long valve open times on its cam timing can run a lower octane than an engine with the same exact static compression ratio that has its valves closed much sooner on the compression stroke. There are good reasons for doing both, and it depends if the engine is being used for highest performance, best fuel economy, or best throttle response; all of those don't necessarily end up at the same parameters. There isn't a great term for this, but "dynamic compression ratio" would be pretty close.

Dave Searle of Motorcycle Consumer News wrote up a great article on this about 6 months back, well worth checking out if you have an interest.

[SpyderGirl]

Originally Posted by Alex

Nope. Isoctane is not an additive, it is a molecule that is inherent in automobile gasoline. It is the reference molecule used to set the base level for 100 RON. Heptane is the reference molecule for 0 RON. All major oil companies have reference blends that have certain percentages of these molecules that are used to determine what level of octane can be expected from the fuel that they are currently producing or testing. For more detail on this, just google ASTM D2699 and ASTM D2700, which are the ASTM tests that determine the ending octane rating.

The additive packages that Banzai was talking about are the tiny amounts of detergent, cleaning agents, and preservatives that are added to the commodity gasoline.



This really isn't a good rule of thumb anymore either. There are 12:1 engines that would immediately self-destruct on 87 and require 91, and there are 15:1 engines that will happily run on 87 all day long. The reason for this is that the static compression ratio is only a matter of how much volume is left in the cylinder from top dead center to bottom dead center. What it doesn't take into account is the valve timing that goes along with this. Think of an extreme case, where the valves stay completely open full-time. As the piston comes up, while the static compression ratio would be determined to be compressing, the charge in the cylinder is actually not being compressed at all as long as the valves are open. The extra pressure escapes. So an engine with a high static compression ratio but with alot of valve overlap and long valve open times on its cam timing can run a lower octane than an engine with the same exact static compression ratio that has its valves closed much sooner on the compression stroke. There are good reasons for doing both, and it depends if the engine is being used for highest performance, best fuel economy, or best throttle response; all of those don't necessarily end up at the same parameters. There isn't a great term for this, but "dynamic compression ratio" would be pretty close.

Dave Searle of Motorcycle Consumer News wrote up a great article on this about 6 months back, well worth checking out if you have an interest.

Thank you for correcting me regarding the isooctane.

And of course, more great information. I will check that article out.

[Alex]

I'm not a gasoline geek, and I don't even play one on TV. My wife is the one that works for Chevron in refinery process planning, and looks over my shoulder to make sure I'm not allowed to say anything incorrect when it comes to gasoline. And if I do she takes great pleasure in correcting me.

[kkim]

so why isn't she posting?

[Alex]

In a sense, she is.

[SpyderGirl]

Originally Posted by Alex

I'm not a gasoline geek, and I don't even play one on TV. My wife is the one that works for Chevron in refinery process planning, and looks over my shoulder to make sure I'm not allowed to say anything incorrect when it comes to gasoline. And if I do she takes great pleasure in correcting me.

ROFLMAO! I just started learning all this stuff a few days ago in school. I am taking automotive tech classes at community college.

[TnNinjaGirl]

Doesn't heat dissapation have something to do with the amount of octane you can safely run in a high compression engine? Like even though our bike have an 11.6:1 which is high for a car, is low for a bike because they are smaller and overall can transfer heat faster, resulting in less "dieseling" of the motor. Thoughts?

[g21-30]

CB...this should answer all your questions:

http://www.popularhotrodding.com/tec...ech/index.html

[tinng321]

Originally Posted by Elfling

@Banzai: Are we seriously going to start with picking on people's grammar/spelling? Look, I know it can be irritating to read. Trust me. But this is a bike forum, not an English forum. Cut people some slack; bikes attract all types, and not everyone types the same way. Also consider not everyone coming to a site like this will be speaking English as their native language. You may be picking on someone who speaks English better than you speak another language.

+1.
I am guilty of not using capital and run on sentences too.
May be I'm just too lazy to use the shift key and don't have the time to keep proof reading my posts.
Who cares how people type/write. As long as one can understand.

[TnNinjaGirl]

Capitilization has nothing to do with it. One could not understand it. The debate was over a page ago. Back to gas.

[Snake]

Originally Posted by Alex

I'm not a gasoline geek, and I don't even play one on TV. My wife is the one that works for Chevron in refinery process planning, and looks over my shoulder to make sure I'm not allowed to say anything incorrect when it comes to gasoline. And if I do she takes great pleasure in correcting me.

Alex, since your wife works for Chevron maybe you can answer this:
Is there any difference buying name brand gas such as Chevron or Shell as opposed to buying from Walmart or Race Track etc. ?

[Alex]

Yes, but perhaps not as large a difference as some folks might think. Gasoline is a commodity. Refineries of all companies sell (and trade) gasoline to all companies to save on transport costs. Companies who put X gallons of gasoline in one end of a pipeline take X gallons out at the other side and call it a day, even though the actual gasoline is different from what they put in. It's a commodity, as long as it meets the same specs, there is no particular difference from which refinery produced it.

But the majors (Chevron/Shell/Exxon/BP/etc) all have their own additive packages that they feel helps the gasoline work better. Not as much for more power, but better cleaning & less likely to affect any of the fuel system components in any negative way. These additive packages are remarkably small, like 0.1% by volume if that, but the majors do feel that the research they put into them do help. Those additives are put in at the final terminal as the gas is loaded to the trucks, so up until that point there really isn't a difference by brand.

Shops like Walmart, Race Track, and other non-branded stations often use the cheapest additive package offered that will allow the final gasoline to meet federal specs. In some cases that may mean no additional additives, but that depends on the state and believe it or not, the time of year.

[lockie]

Never though talk of gasoline could be so interesting. I have nothing to add I'm afraid but I've enjoyed reading the discussion. Thanks

[Snake]

Thanks Alex I appreciate the education were all getting here.

[backinthesaddleagain]

Originally Posted by Broom

in his defense, he's above average than most of what you read online these days. i'm super guilty of not using capitals... and sometimes using ellipsis instead of forming a proper sentence, but i still try to use decent spelling and grammar when i can

agreed.

[backinthesaddleagain]

I wAs UsInG 91, tHeN sWiTcHeD tO 87 fOr 2 TaNkFuLs (ok that is hard to read and I APLOGIZE). I thought I heard some detonation at 87, and have used 89 for the last couple tankfuls. Will try 87 again, maybe just got some bad gas?

[Broom]

Originally Posted by backinthesaddleagain

I wAs UsInG 91, tHeN sWiTcHeD tO 87 fOr 2 TaNkFuLs

haha... i HATE that crap!

[wyckedflesh]

Here in the Desert, From May to Oct they add a higher percentage of MTBE to the fuel. When that time hits, I have found that if I don't switch to 91, I start getting ping on take off from the lights. Course, it doesn't help when the ambiant temp is running over 100F. Been lucky the last couple of weeks and temps dropped back down. Dropped back to 87 with no problems so far.

[Ramen]

87 works just fine for me. The only advice on gasoline I can offer is to try to find a station that doesn't use ethanol.

Unfortunately, in Florida, the gub'mint mandated all stations to use ethanol.

[noche_caliente]

Sean - try the Shell stations - afaik they are trying their best to get around it - it's the only spot around here that has ethanol-free gas

[Ramen]

Originally Posted by noche_caliente

Sean - try the Shell stations - afaik they are trying their best to get around it - it's the only spot around here that has ethanol-free gas

I prefer Shell gas as well (figured if their gas is as good as their Rotella oil, why not), but every Shell I've visited also has that "contains up to 10% ethanol" sticker on their pumps.

[Kurosaki]

Originally Posted by Alex

This thread is the first time I've ever heard that lead was harmful to aluminum engine components, and I'd like to read more about it before taking it in as accurate new info.

^+1

Only issues you'll have is a destroyed cat converter.

The motor itself will be fine...


If you don't have a cat, no problem.