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Am I a dufus .... octane rip-off ???


mefly2

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As the weather has warmed up here in Montana, I have noticed a bit of pinging / rattle from the engine at times. As I do not always want to downshift, I thought that a better grade of fuel might be in order.

 

Previously, when the RT's tank was empty, I would fill up with the mid grade out of a three grade dispenser pump. Lately, I have wanted to remove the palstic to add some farkles and have been working on the "bottom half" of the tank ... trying to keep just a few gallons in it and run until the light comes on for low fuel. Then add a couple of gallons, etc, etc.

 

However, I just realized that we are no longer in the three separate pump world ... with a couple of the separate pumps dispensing regular / unleaded, one with mid-grade, and another with the super/high-test/ethyl (yes, it used to be called ethyl in the pre-unleaded days ... that is not just my aunt).

 

So, my efforts were substntially wasted in purchasing the small amounts of higher octane fuel ... or, at least seriously diluted by all of the previous purchaser's fuel selection being held in the line from the actual pump unit to the top of the dispenser and down the hose to the nozzle ... my guess is that the complete assembly holds somewhere between 1.5 and four gallons. YMMV

 

The only way around it - from my perspective - was to select the higher octane fuel ... pump 5-6 gallons into my wife's jeep (to get all of the lower grade fuel purged from the dispensing lines) ... then, at the same pump - add fuel to my 1150RT (or gas container for later use) ... pay for the fuel ... AND, then select the lower grade fuel and add more to her jeep (thus allowing me to collect the more expensive fuel that already was in the hose / dispensing unit ... but at the lower grade cost ... excuse my rambling, but I feel substantially ripped of by multiple vendors. YMMV

 

No place around here at least has the separate pumps for each grade any more. frown.gif

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So, my efforts were substntially wasted in purchasing the small amounts of higher octane fuel ... or, at least seriously diluted by all of the previous purchaser's fuel selection being held in the line from the actual pump unit to the top of the dispenser and down the hose to the nozzle ... my guess is that the complete assembly holds somewhere between 1.5 and four gallons. YMMV
This has been discussed before but it's an interesting question. I'm not sure how much dilution occurs but it seems reasonable that for a relatively small fill like a motorcycle tank it could be significant. We're not talking about much in terms of money but I wonder how much a higher octane level a motorcycle really sees when choosing premium when the prior fillup was with regular (as I would guess that most of them are.)
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ShovelStrokeEd

I don't think the entire volume would amount to more than 1/2 gallon or so, certainly not requiring 4-5 gallons of pumping to get clear. Of course my bike runs fine on 87 octane (its a Honda) so this isn't an issue for me.

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It appears as though you are neither a dufus or getting ripped off ... much. The answer you seek.
That would be correct assuming that the only volume that needs to be considered is in the hose itself. Perhaps this is the case as I don't know for sure how the internal mechanics of switching grades works... I hope the author of the article does. wink.gif
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For the gas to stay in the line a vacuum would have to hold it there. All gas tanks are vented, so all the gas runs back into the storage tank, except for the amount in the hose (after the bend in the meter box). The max amount left in the hose would be from the height of the nozzle, to an equal height of the bent hose. That's physics.

 

OP, worry about something else that really matters.

 

BTW, you can easily empty that portion by lifting the hose bend higher than your gas cap height, gravity will push it out.

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It appears as though you are neither a dufus or getting ripped off ... much. The answer you seek.

 

Using this math you are losing about 2 tenths of the octane through dilution on a 5 gallon fillup. So for 91 octane like here in Cali your talking 90.8. Probably won't make any difference.

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duckbubbles

I can't remember where, but I saw this reported on some while ago. It was concluded that there was between 1/2 gal. and 3/4 gallon of the last purchase in the lines to the valves that you get first. It seems that the cage driving public doesn't care too much.

Many of the stations have pumps that display the price per gallon of the last purchase. I cruise around the pumps until I find one that at least has pumped some mid-grade if there is one. My Ducati doesn't like premium in some instances and putting some regular in definitely let's me know about it.

It's cheaper for the stations to maintain one third the number of pumps so that is probably the bottom line and don't expect to see anything different in the future.

I remember seeing a Sonoco (I think) pump way in the past with seven different grade selections on it!

Just returned from Arkansas/Missouri and ran across one old style mechanical pump that charged by the half gallon. The proprietor told of many people being really pissed off after they found that they weren't getting half price gas, although there was a sign, plain as day, right on the pump stating such.

 

Frank

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russell_bynum
I agree with RAGS cool.gif

Don't worry about it.

 

+1

 

Sometimes I'd swear you guys aren't happy unless you've got something to fret about.

 

Just put gas in the damn thing and ride.

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For the gas to stay in the line a vacuum would have to hold it there. All gas tanks are vented, so all the gas runs back into the storage tank, except for the amount in the hose (after the bend in the meter box). The max amount left in the hose would be from the height of the nozzle, to an equal height of the bent hose. That's physics.

 

OP, worry about something that really matters .

 

BTW, you can easily empty that portion by lifting the hose bend higher than your gas cap height, gravity will push it out.

 

Perhaps my first estimate was a bit (OK, a lot) too high, (Sorry Rags) but even ~.4 gal diluted into a 2 gal purchase is significant to me. This does matter to me and my RT ! The fuel at the retail outlets does NOT run back into the tanks - otherwise the pump would need to be primed nearly every time it was used. There is a check valve between the nozzle and the hose to prevent folks from draining the hose (that is why you will feel a slight swelling in the hose as you pull and release the nozzle and the system goes back up to pressure. If the check valve were not there many folks would "try to drain the hose". I remember watching and smirking as people tried to get something for nothing by lifting the hose and squeezing the nozzle at our last gas station outlet ... they did not realize that the check valve is mandated by fire codes to prevent just such gas drainage! I spent about 25 years in the retail petroleum industry with three different outlets at one time ... back in the days of single dispenser pumps.

 

A little math (Assuming a 10-foot filling hose with an internal diameter of 3/4 inch, the amount of regular gasoline would be 0.229 gallons (V = pr2h, or 3.14 x (0.375 in.)2 x 120 in. x 0.00433 gal/in.3 ) is a good start, but the internal diameter is closer to one inch and the run is 15+ feet plus the residual in the pump, itself ... and you will see what I was talking about in the significant amount of fuel in the distribution ... from the actual pump at ground level to the top of the dispenser (usually at around 7-8 ft above ground) as well as the amount of fuel in the hose from the top of the dispenser (where the hose is attached) and back down to the nozzle. That analysis does NOT take into account if there is a manifold distribution switch over to the dispensing unit (does anyone know?). To me, a significant amount of dilution if the RT tank is nearing empty and only a few gallons are added.

 

For some, this may not be a consideration, but that is why we have this forum ... to ask a question and read relevant responses from others ... just my caveat to those who choose to pay a bit more for the higher octane and may not be getting what they thought that they were paying for ! Thanks to those who offered constructive alternatives ... you will spot me by my circling to find a pump dispalying the last purchase of at least mid-grade ...

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Of course, you could just stick around after you fill up and get reimbursed the difference from the person who uses the pump after you. lmao.gif

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However, I just realized that we are no longer in the three separate pump world ... with a couple of the separate pumps dispensing regular / unleaded, one with mid-grade, and another with the super/high-test/ethyl (yes, it used to be called ethyl in the pre-unleaded days ... that is not just my aunt).

It was called "Ethyl" because the antiknock agent "Tetraethyl Lead" was added. A lead-free gas cannot actually be "ethyl".

 

Useless fact of the day.

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Here's a related question that I've wondered about lately. What are the real-world implications of using lower-octane fuel in an 1150RT? I know that many cars now have knock sensors as part of their engine management systems, meaning that lower-octane fuel is automatically compensated for and the only real effect is a slight loss of power. Is this true of oilheads as well, or must the octane recommendation be religiously adhered to? Anyone know?

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If the tiny bit of residual fuel in the hose TRULY didn't matter, then they'd dispense diesel out of the same hose as the gasoline.

<diesel+gas comment deleted - >

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russell_bynum
Here's a related question that I've wondered about lately. What are the real-world implications of using lower-octane fuel in an 1150RT? I know that many cars now have knock sensors as part of their engine management systems, meaning that lower-octane fuel is automatically compensated for and the only real effect is a slight loss of power. Is this true of oilheads as well, or must the octane recommendation be religiously adhered to? Anyone know?

 

There's no knock sensor on an oilhead.

 

I believe the GS models have a jumper that lets you run them on really crappy gas...like if you're in the middle of the Sahara and the only thing you can find is 78 octane in a barrel strapped to the back of a camel or something like that. Other than that, you have to use an appropriate octane level.

 

Personally, I think this whole discussion is silly.

 

I loved the OP who has his wife go with him to get gas so he can shuffle back and forth between gas pumps, his bike, and her vehicle. That must be a boatload of fun having to pull her away from whatever she's doing everytime he needs gas. What happens on long trips...does she follow along behind him in her car? lmao.gif

 

Really people. Put gas in it and ride the damn thing.

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Joe Frickin' Friday
Here's a related question that I've wondered about lately. What are the real-world implications of using lower-octane fuel in an 1150RT? I know that many cars now have knock sensors as part of their engine management systems, meaning that lower-octane fuel is automatically compensated for and the only real effect is a slight loss of power. Is this true of oilheads as well, or must the octane recommendation be religiously adhered to? Anyone know?

 

As Russell notes, there's no knock sensor on the oilhead bikes. Without a knock sensor, the best performance (i.e. max power, and minimum cost) is had by running the engine on the lowest octane fuel it will tolerate without knocking. Higher octane fuels sometimes are made that way by the addition of alcohol, which lowers the per-gallon energy content; that limits maximum power output of the engine and also miles-per-gallon. So if your bike runs "fine" on 90-octane ("fine" meaning no, or very little, knock), it's a waste of money to pay extra for 92-octane, especially if it's got reduced energy content.

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Paul Mihalka

Mitch, +1. I've run my R1100RT, my R1150R, and now my R1200GS always on regular gas. I never heard any of them knock, even without earplugs wink.gif . I don't ride in stop and go traffic, I don't open the throttle much at low rpm and do open it wide once in a while at high rpm, so my bike's carbon build-up must be low. Carbon build-up is the main reason for knocking/self-ignition. Now with the R1200 I really don't have a problem as it has the knock sensor.

Plus if somebody in front of me fills up with premium at a single-hose pump, I get a bonus grin.gif

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...Personally, I think this whole discussion is silly.

 

I loved the OP who has his wife go with him to get gas so he can shuffle back and forth between gas pumps, his bike, and her vehicle. That must be a boatload of fun having to pull her away from whatever she's doing everytime he needs gas. What happens on long trips...does she follow along behind him in her car? lmao.gif

 

Really people. Put gas in it and ride the damn thing.

No, Russel, sarcasm is not necessary. I simply wanted to get higher grade fuel to see just how my RT responded. As for gassing on long trips ... well, since my wife rides with me ... I guess that we could try to trailer another vehicle behind us just for dumping gas into when we fill! lmao.gif Reality check!

 

Sorry to respond in kind, but my wife is my partner and we were out on the bike 2-up together when we did the fill ... then we rode the two blocks home to get her jeep and be able to put the higher octane fuel into the RT.

 

My mistake; I thought that I had made a sincere inquiry from casual observation. Still a great site, but ... no flames needed.

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