The Down Range Forum
Member Section => Down Range Cafe => Topic started by: SwoopSJ on July 27, 2008, 12:19:13 AM
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Gas prices are now beginning to come down a little, but I unfortunately never thought to post this before. Along with maintaining correct tire pressure you can save money by not pumping your gas full tilt. This probably doesn't apply to every pump, as some are noticeably slower than others, but here is the short explanation. When the pump is operating too quickly, cavitation occurs (tiny bubbles forming in the liquid gasoline). This is due to the vapor pressure of the gasoline exceeding the external force(s) which maintain its liquid phase at stp. When this liquid to vapor change occurs, while pumping, the volume of the gasoline is substantially increased (can't remember the exact factor), it then decreases when these bubbles return to liquid in your tank. To make a long story short(er), when you pump too fast, cavitation causes you to pay for gasoline that you aren't actually recieving. Also, if you can, buy gas during the cooler times of the day (morning & evening) as temp affects volume too. Most pumps are now volume adjusted to 60 F, but every penny counts. Now you can afford more ammo! ;D
Swoop
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Good points !
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That makes sense I'll try that.
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Probably just another internet rumor....... Did you hear about this in a forwarded email?
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If you've ever ridden a motorcycle you know it's true. I have 'overfilled' the tank on a MC this way. Lawnmower. too.
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My understanding is that new style pumps used since the late 70's no longer have the cavitation issues, so trust that is taken care of through certification and testing. Up here in the beautiful state of Minnesota we don't worry about temp except for over fill. All our tanks are three feet underground (at the top, and then you remember that they are ten feet in diameter ... they are cool year round). If you top your car off at 7 PM (as the heat of the day is starting to wain) and drive two blocks to park in the garage you will find a gas spot on the floor within two hours. If you fill your bike or a gas can in the evening you will feel the cold, and on a humid day you will get your tank covered with condensation.
I put more faith in driving sensibly and not spilling by trying to top off (allow the automatic shut off to shut off no more than three times).
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Probably just another internet rumor....... Did you hear about this in a forwarded email?
No. One of the degrees I hold is in petrochemical operations. I don't utilize that information much anymore, but it does come in handy every now and then.
Swoop
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No. One of the degrees I hold is in petrochemical operations. I don't utilize that information much anymore, but it does come in handy every now and then.
Swoop
Wow! :o That shut me the hell up real quick like!
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Wow! :o That shut me the hell up real quick like!
Don't feel bad, I can't even pronounce it ;D
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Don't feel bad, I can't even pronounce it ;D
Now thats funny, right there.
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Petro-WHAT????? :o
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Sorry m58,but Swoop is correct. Neither the cavitation or hot fuel problems have been solved.
ALL purchasers are being affected financially by both.In other words; You AINT gettin' what ya paid for. Even in Minnesota.
Yes the pumps are certified to be accurate.But,that's only at the SLOWEST rate of fill and then ONLY at a fuel temp of 60°.
Only thing is,fuel is NEVER pumped at that rate and temperature.
OOIDA (http://www.ooida.com) has been working diligently in an attempt to have both problems rectified.
Keep in mind that it's VERY hard to persuade oil companies to stop taking extra profits on every gallon of gas/diesel sold.
You can read an article about the "hot fuel" issue Here (http://www.landlinemag.com/Archives/2008/July08/News/hot_fuel.htm).
Jim
I may not be a Petrochemical Engineer,but I AM an OTR Driver and I DID stay at a Holiday Inn Express last night. ;D
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When I pumped gas recently I noticed a sign on the pump that said this pump is regulated to provide 231 cubic inches or something like that. What does that mean to this discussion?
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When I pumped gas recently I noticed a sign on the pump that said this pump is regulated to provide 231 cubic inches or something like that. What does that mean to this discussion?
My field of study was more along the lines of distillation and refining of petroleum and chemical products, so I am not what you would consider an expert in retail distribution (never worked for dept. of weights and measure which is responsible for regulations on pumps). That being said, I believe what you are referring to is the "tested" flow rate of the pump. I'm not sure if that is done by actual volume comparison or mathmatically which are vastly different. I believe this rating is mostly to show compliance with the ORVR ( onboard refuelling vapor recovery) systems, which are supposed to reduce pollution during refuelling. Yes, the flow rate definitely has an effect on the presence or lack of cavitation in a system, but there are many other factors at play, also. Although educated for, it has been a long time since I worked in this field, so don't take my word as absolute gospel. I do have my bouts with C.R.S. syndrome. ::) I am, however, willing to share what knowledge I have or don my ignorance for all to see. Probably the latter. ;D
Swoop
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When I was in my teens my Dad drove a tanker delivering to gas stations around NH and Ma. When I heard people say "I never buy that crappy brand "A" gas I only use brand "B" I would laugh, having seen both brands being loaded from the same pump. But brand "B" was 2 or 3 cents more per gallon ;D
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I only use brand "B" I would laugh, having seen both brands being loaded from the same pump. But brand "B" was 2 or 3 cents more per gallon ;D
Having never owned a car( I don't have a license to drive one), but riding bikes most of my adult life, I can't comment on how various brands of gas would affect cars, but I have noticed differences in how various brands of gas would do in my bikes.
For the record: my bikes included a Yamaha XJ600F, Yamaha SRX 6, Honda XBR500/GB500TT, Honda CB750KZ, Honda CBX-1000, BMW R100RS (never should have sold that one (http://www.clicksmilies.com/s1106/sauer/angry-smiley-022.gif)) and a Italjet Formula 125 scooter.
Most brands would bring similar results in MPG, but using for example Shell gas in my CBX, Yamaha's and BMW would result in a higher fuel consumption, where as Mobil gas would do the opposite. I realise that this is not a scientific study, but I think it might be smart just to experiment with various brands and keeping record of various fuel consumption figures.
Ocin.
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I think Rastus and Swoop will confirm that all gasoline is refined the same way (at least in the US) I know that Mobiles additive is a small test tube dumped into 8000 gallons.
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I think Rastus and Swoop will confirm that all gasoline is refined the same way (at least in the US) I know that Mobiles additive is a small test tube dumped into 8000 gallons.
Yep. The only difference, in my experience, between the different brands of gasoline is the additives they have mixed in. At least all brands which share a common refinery. They are all distilled and refined in the same manner. In my area, the only gasoline that is not from the exact same crude stock, is Shell. It is shipped from Cincinnati. Exxon is also shipped here from WV, but only because they send it there, from here, by barge, to mix in their additives. (Pretty cost effective, huh? ???)
Swoop
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When I pumped gas recently I noticed a sign on the pump that said this pump is regulated to provide 231 cubic inches or something like that. What does that mean to this discussion?
231 cubic inches is equal to one US gallon.
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You can also check internet rumors about gasoline at Snopes. http://www.snopes.com/inboxer/household/gastips.asp
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You can also check internet rumors about gasoline at Snopes. http://www.snopes.com/inboxer/household/gastips.asp
???
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???
Those are just a few of the gas saving tips people keep emailing each other. There are about a dozen that I've seen so far. If your time is less important than money, you may save a few cents while wasting several minutes pumping gas slowly. None of the other tips I've heard of work, but that one might.