gas octane for Like 200i - a chemical engineer

[Vivo]

I just use 87 in my Grand Vista and don't have any knocking.

What I wonder is how much gas the pump hose contains from the previous customer. Since I only add 1.5 gallons at the most at a fillup, how much of that is whatever octane was pumped before?

It's one hose per pump per fuel type, right?   

[AVGuy]

All the pumps around here have 1 hose per pump. All 3 grades are delivered through the same hose. I just googled it and one source said a typical gas pump hose holds about 1/3 gallon of fuel. That's a fairly big percentage out of 1 or 1.5 gallons of gas.

[Vivo]

All the pumps around here have 1 hose per pump. All 3 grades are delivered through the same hose. I just googled it and one source said a typical gas pump hose holds about 1/3 gallon of fuel. That's a fairly big percentage out of 1 or 1.5 gallons of gas.

Hmm... haven't seen that type of pump... 3 grades using one hose? We usually have one hose per grade and it's even color coded...

[AVGuy]

Here's what most of the pumps in my area look like. All three grades go through one common hose.

[Vivo]

Interesting... so, what are the citizen doing about it?  If the previous person filled-up with low octane and the next with high octane and part of it (in the hose) in low octane... that's over pricing, right?  And there's a problem with motorcycles as you previously mentioned... maybe you just have to stick with regular gas...

[91cavgt]

I just use 87 in my Grand Vista and don't have any knocking.

What I wonder is how much gas the pump hose contains from the previous customer. Since I only add 1.5 gallons at the most at a fillup, how much of that is whatever octane was pumped before?

I have been told by several people that the gas hose holds about 1/3 of a gallon of whatever gas the last person pumped. 



As far as the octane debate, I believe with our fuel injection that in moderate to cold weather we can probably run 87 octane with absolutely zero problems.  However, if you live in an area that gets really hot then it might be wise to run premium during those times to help prevent detonation.  I do not know the limits of the stock computer to retard ignition timing due to intake air tempuratures.  I have not seen a knock sensor listed on the list of engine sensors our computers use and I have not seen one mounted on the engine either, so this is why I would personally rather run the higher octane fuel both in the hot weather and during engine break in.   

[AVGuy]

Interesting... so, what are the citizen doing about it?  If the previous person filled-up with low octane and the next with high octane and part of it (in the hose) in low octane... that's over pricing, right?  And there's a problem with motorcycles as you previously mentioned... maybe you just have to stick with regular gas...

I've never heard one complaint about these pumps, its just the way they are. And people filling up their cars or trucks with 12 gallons or more don't even think about any residual fuel left in the hose.

I ride a 09 Grand Vista which is not fuel injected and use 87 all the time with no problems. I've read on other discussions that 87 octane in the US is the same as 91 in other countries, but don't know how true that is.

[MotoRandy123]

It's going to be even worst when they start putting the 15% ethanol through those hoses...

[Vivo]

I ride a 09 Grand Vista which is not fuel injected and use 87 all the time with no problems. I've read on other discussions that 87 octane in the US is the same as 91 in other countries, but don't know how true that is.

In the U.S. they use RON+MON/2 or Research Octane Number plus Motor Octane Number divided by two...  or they also call it  A.K.I.  = Anti-Knock Index....   In other countries, they only use RON....  So, in short...  the U.S. uses an average figure compared to other countries.... 87 in the U.S. ranges in the 91-92 in other countries... it's just an estimate because actual figures are not readily available... it could be 90....