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Gas question

1K views 41 replies 24 participants last post by  LsilverR1 
#1 ·
I have a friend that will only go to gas stations with three seperate nozzles, one for each grade of fuel. He claims that the pumps with one nozzle and the buttons to select the fuel grade leave gas trapped in the line from the last user. 90% of the time this would be 87 and when we fill our bikes with premium our tank is full by the time the higher octane gas that we are paying for actually makes it to the nozzle. I thought it was BS, but the more I think about it the more sense it makes. Does onyone know how those pumps actually work and is it possible that I've been paying the premium price for regular gas?
 
#9 ·
Is it true that you should not pump gas from a station that's getting refilled? Somethng about the deposits?
 
#10 ·
Ok, so. The "debris myth" about filling up while a tanker is filling the pump. How often do you see gas stations being refurbished with new tanks? A lot, huh? yup, they're pretty damn clean. And you really think that there are no more filters from the main tank to the nozzle? I dunno, but I'm not sweating it.

So paranoid robbie.
 
#11 ·
I've actually heard this story too... from some crazy guy's website about how awesome the Harley Roadking is. He went into a LOT of detail about not only this, but also how to best preach to people about Jesus at bike rallies. Suffice it to say, I did not take it as a reliable source.

I doubt it really matters either way though. If it makes you happy to use pumps with 3 lines, then go for it. If you've filled up at pumps with 1 nozzle before and haven't heard any pinging, then it's probably not a big issue.

Ride more and worry less.
 
#12 ·
You don't need to run a high octane fuel people!!!!

Read this entire article.

http://www.motorcycleperf.com/techtips/gasoline.htm

1.) OCTANE

This is the resistance to detonation the gasoline offers. The most common grades of gasoline are: REGULAR at 87 Octane; MID-GRADE at 87-90 Octane; PREMIUM at generally 93 Octane. Other custom-built racing gasolines can offer up to 125 Octane. Octane is an indicator of the speed at which the gasoline burns in the engine.

The higher the octane, the slower the speed of the burn; the lower the octane the faster the burn. If the burn is too fast, uncontrolled combustion can occur. This most often is heard as “pinging” and is commonly referred to as detonation. This is because instead of burning through top dead center of the combustion stroke, the entire charge is ignited too early and explodes in the chamber and acts as a bomb. Conversely, if the speed of the burn is too slow, it continues after the useful work can be done in the motor and manifests itself as poor throttle response, reduced power output and increased emissions and fuel consumption. An engineering fact: THE MOST HORSEPOWER IS MADE AT THE THRESHOLD OF DETONATION. We have often gained horsepower on the dyno and felt improved starting and driveability going from Premium grade gas to Regular. This change was recently quantified in a customer’s Ducati M900 by reducing the cranking time to start-up from 15 to 3 revolutions, although part of the improvement is explained below.

The multi-valve combustion chambers and their reduced flame front propagation distances in the modern engines virtually eliminates the need for high-octane gasoline.
 
#13 ·
When you buy a roast and ask for it to be 'ground' at the meat market, the butcher is supposed to feed through a piece of 'leader' meat to 'push out' the leftover shit from the last customer that is hanging out in the worm/blade head.. I can understand the validity to this thought process.
 
#14 ·
Grasshopper also speaks the truth. It's a myth that higher Octane means more power. The reason that higher octane is used in "race" engines is because of compression. High performance engines have higher compression, which can lead to premature ignition if using lower octane fuel. Higher octane gas resists burning, which is useful in high compression engines.

You're best bet is to just check your owner's manual and use the grade it recommends. You might be robbing yourself of power and money by putting premium in tank when mid-grade or regular will suffice.
 
#16 ·
Higher octane also allows more aggressive ignition timing maps. Greater ignition advance = greater power (to a point).

If bikes came equipped with knock sensors, we can all run 87 without fear of damage. Most high compression engines are in the neighborhood of 11:1 or higher, for which premium is typically recommended. Of course, if you flip your bikes every year or two, the damage may not show up for some time.

As for fueling up while the tanking is pumping, yes there are filters in place. When was the last time it was changed. How do you know the fuel is not already going through the bypass valve? With the FI'd bikes, you can't run an inline filter like you could with the gravity fed types. Other than the screen at the fuel pickup inside the tank, what else is filtering the fuel before it reaches the injectors.
 
#17 ·
Higher octane also allows more aggressive ignition timing maps. Greater ignition advance = greater power (to a point).

If bikes came equipped with knock sensors, we can all run 87 without fear of damage. Most high compression engines are in the neighborhood of 11:1 or higher, for which premium is typically recommended. Of course, if you flip your bikes every year or two, the damage may not show up for some time.

i agree with the first line.

not with the second. no way i want to run 87 high performance cars jsut because it has a knock sensor.
 
#27 · (Edited)
If you never get on the throttle hard, never even get half way to redline, why the extra expense then? Sure you'll be losing some power, but if your driving style doesn't benefit anything from it what are you gaining?
While there may be truth to your theory, the problem is with pre-ignition. Lets say you fill your tank with 87 octane in your performance car. You step on the gas, engine speeds increase, so does timing. Soon, that highly volatile 87 octane starts going off just a little too early. So the knock sensor detects pre-ignition, the computer tells the ignition system to pull timing to stop the p[re-ignition, and your engine starts to run less efficiently. Now you have an engine that may be running on cheaper fuel, however is now running less efficient because it can not advance the timing to get proper burn. So your cheaper gas is now providing you less mileage per gallon due to improper ignition timing, and your fuel mileage suffers. You now have to fill your tank more often, your valves, spark plugs, and (in the case of direct injection engines) your injectors start getting plugged up with soot from the inefficient burn of your low octane fuel, and the performance, and efficiency, of your engine further decreases. Now, your car, which may have made 250 horsepower and gotten 30 MPG when new, is making at best 200 horsepower (remember that ignition timing issue) and is probably experiencing somewhere in the low to mid 20's MPG. Not to mention, your spark plugs need to be replaced more often, you are probably in dyre need of injector cleaner to make them run better, etc...


Moral of the story is: you can run 87 octane if you want, but you are better off running the proper fuel for your engine.
 
#26 ·
Really doubt stations have more than 2 tanks underground. Ones for 87, ones for premium. Even with 3 nozzles mid grade is made by mixing reg and premium in the pump. All 3 nozzles does is let people still use the pump if one nozzle is broke. If a 1 nozzle pump breaks down, stations cant make any money on it until its fixed (and right now I hear its gonna take a while since the repair companies are fixing the pumps that cant register over $3.99/gal) unlike a 3 nozzle pump where the other 2 still work.

Now diesel should be on a separate pump altogether. We have a few up here where diesel is right next to premium and both have yellow handles.
 
#28 ·
Todays pumps can be very sophisticated, and can dispense multiple single grades and blend grades; see

http://www.ncwm.net/ntep/certificate/99-045A5.pdf

A single hose pump has about .2 to .3 gallons in the line. Dilution then equates to approximately 8.6% between 87 & 93 octane for an average of 4 gallons. For 93 that means it drops to no lower than 92.4 ignoring what is already in the tank. Not a big deal usually.

I always use 89, so I get a boost if the prior fill was higher octane. Then again, lower octane means a faster, cleaner burn... Luv that burn...
 
#29 ·
Vtec,

All good points in your post in theory :) My camaro z28 with the 5.7L LT1 calls for premium. Few years ago when fuel was cheap, I did an experiment running 15 tankfuls (almost complete tanks) of 93, then 15 of 87. With my driving style, there was no noticeable increase in fuel economy with 93 vs 87 (combined city & hwy). On a different car, results may of course be different. Perhaps I wasn't driving the car hard enough to the point where more aggressive timing maps would have made the difference. It's a 6spd, I typically shift between 2 and 2500.
 
#30 ·
It is a GOOD idea NOT to fill up while the ground tanks are being refilled. It's not the dirt or debri that will get you, it's the water that is churned up from the condensation at the bottom of the tank that might ruin your day. Always wait for the gas truck to finish and give a few minutes at least for the water to settle before pumpin' your gas.

I worked at a gas station way back when and there was always some water in the tanks when I'd stick them to check the level. In the olden days we did that with a big, long stick. At the bottom we'd smear some chemical that would turn red if it detected water. There was always a little water in each tank.
 
#34 ·
I don't worry about how many lines the station has, but i can't and won't run under 93 unless I have to which has happened once and the bike ran like crap. R1's call for 93 as I think alot of the newer bikes now? I know my Honda's ran on 87 but not this bike.
 
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