My Harley really likes 93 octane (or higher). It sputters a little but runs OK on 87 or 89. Nearly every time I can and bother to check, I see that the customer before me purchased 87 octane. The stock sportster tank is 2 gallons with 1/2 gallon reserve. That's right - 2 gallons.

So the delema is: when the customer ahead of me pumped 87 octane then I select 93 and pump 2 gallons, how much of that is 87 octane left in the hose/pump from the previous transaction? I'm sure it varies from one type of pump to another. I'm guessing it might be a gallon - so I wind up with something like 90 octane. Anybody got facts?

 

hardly a gallon. more or less a few ounces.

 

Assume the following:

Hose ID = .625"
Hose length and pump plumbing = 14' (168")

Given:

1 gallon = 231 in^3

Therefore, the fuel in the gas pump plumbing and hose = .22 gallons

**If it's 1/2" ID plumbing then the result is .14 gallons.

 

Really?!?! Gee, those hoses can be like 12 feet long on some of those things (the ones that hang from above the pump). Then I figure the pump is at like knee level so the plumbing has to get back down to that level too. Then who knows how much might be in the pump. Finally, the 87/89/93 junction has to be 'south' of the pump right? I know those hoses have a much smaller inside diameter due to all the insulation and vapor return and such.

Is this a guess or do you really know about this stuff?

 

not really a guess. i did pump repair and tank removal for a friends business for a while. we got a lot of calls when MTBE was outlawed and all the tanks had to come out. we also had to pull the pumps to re seal them and ship them off to get recertified.

 

Your guess about the Gallon might be a little high, but you can´t make an average out of the two different octanes, the mix will just be a little lower in quality than a full 93 tank

 

Why not just go to a gas station that has an individual hose for each octane rating?

 

I've confirmed with a local gas station that I sometimes visit (Chevron) that the switch in question is in the pump. There are two lines leading to the pump; mid grade is blended at the pump.

 

OK, now we're getting somewhere! If that computation holds then worst case I get 7/8 tank of the good stuff. Perhaps nothing to lose sleep over. I've been getting away with it for years so it can't be a big problem for the bike. I always wondered how much $$ I was wasting though. .22 times maybe $0.50 difference in price - sounds like only a couple nickles per fillup or $75.00 total since I bought the bike in '90. Man, that's almost a new set of drag pipes!

 

Ya, I love it when I see one of those. I get to keep my dime and feed my horse the good stuff! Trouble is I have to drive 30 miles to find one of those, by the time I get home I need to refill again! j/k they are quite rare these days, often they are 'off brands' too. There is a larger tank option but I don't like the look.

 

I always flip the handle off, then pull the trigger again to get that last little bit out myself. I don't like giving it to someone else. Can't do that on some of the newer pumps though.

 

Snake is exactly right. If you look around on the pump, they normally come with an "Emergency stop" or a "safety stop button" that will shut the pump down, and then you can squeeze the handle and get the last bit of gas that you paid for, but is still in the line.

If there is no button, you can always stick you hand up against the flap inside the pump that tells the pump you've put the nozzle back... and then squeeze that little bit of gas out thats still in the line.

 

As I recall, there is not much gas in the hose. Many years ago, I bought my first motor vehicle, a Whizzer motorbike. Since I was always broke as a kid, I would make the rounds of the gas stations draining the hoses into my 1 gallon tank. It took many stops, but it kept me going.
Dono

 

Got my 1st HD in 78.Now I have a 80 FLT got it in 83,also a 01 FLHTC p/u in Dec 00,I just run 89 in them no problems,some times I put in a oz or two of sea foam to clean the carbs,bought my wife a 883 in 86,put a super gluide tank on it so she could go on longer rides,to me their is no big differance except the 20 cents per gal differance,if your into FULL THROTTLE go with 91-92 octain other then that,no sence losing sleep over it.The 1.9 gal sporty tank stinks,90 miles down the road on a fun run and all you want is a gas station,no fun there.
KEEP THE RUBBER SIDE DOWN.
LOUD PIPES SAVE LIFES.
and last but not least what I have on both my baggers.
D I L L I G A F !!!!!!!!!

 

If it's already in the hose, wouldn't it be gas that the guy before you paid for? So you're getting a very small amount of free gas.