Separate pumps for each fuel grade or one for all grades?

[Intelman34]

I always try to fill up with the highest octane fuel possible at the local pumps as my car requires premium.

I've always wondered... how much better is it to fill up at a station that uses a separate nozzle for each grade of fuel than the ones that have a single nozzle for all grades? It seems like a few gallons of "whatever" would come out of the combined nozzle pumps before the 93 octane that I am paying for comes up.

Is it logical to think this?

The separate nozzle pumps are getting harder and harder to find.

 

[eljefino]

I bet it's more like a quart. The thickness of the hose isn't all full of outward bound gas; there are some vapor lines etc in there too.

Best to just run down near "E" so you buy more gas at a given time, and dilute the effect of some pauper's fuel.

If you cruise around all the gas station islands, you can see how much gas was dispensed and what was paid by the previous customer. Do the math in your head quickly and you'll see if they bought premium.

 

[labman]

Do a search. The last time this topic came up, I did some calculations on how much gas would be in the hose.

 

[Shannow]

Read an article a few (many actually), on a TVR sportscar, being tested in the UK.

They were told to use "brand X" petrol, and only their premium, as that was what the engine was tuned for.

Allegedly, they filled up, and there was knocking taking place that wasn't there previously.

Apparently it was a mixer type pump that they used, as opposed to a dedicated pump/nozzle.

 

[T-Keith]

I've heard it can be quite a bit, if your only filling a few gallons it can make a difference. Very few stations have seporate hoses anymore, the amount would probably depend on design.

-T

 

[Racerjk]

I always try to find a pump where the last person bought premium. You can't always find one though!!

 

[Bobert]

The Phillips 66 station down the road from me has separate nozzles for each grade. The station is an older station though, so maybe the newer stations have the combined nozzle.

If your car is very sensitive to octane (chipped cars especially), I suppose carrying around a 1 gallon gas can might not be a bad idea for the times when you have to use those combined pumps. Probably a half gallon would get rid of the lower grade fuel still in the lines. Just use the extra gas in one of your other cars which doesn't require premium, or use it in your lawn equipment.

I like Phillips also (Citgo too) since each grade is not 10 cents higher than the next. I think Plus is 8 cents higher than Regular, and Premium is 7 cents higher than Plus.

[ March 04, 2005, 03:13 AM: Message edited by: Bobert ]

 

[Ignatz]

There called blender valves. I test underground tanks and lines for a living. When I test lines at a station with blenders I always test the regular and premium lines comming in to the dispenser at the same time because blender valves many times bleed together. Some sites flat out have bad valves. I try to fill up my BMW motorcycle and my old Saab turbo at stations with separate hoses. The local government regulators are more worried about weights and measure issues than octane levels. Yes separate hoses are more expensive because of needing 3 storage tanks (regular,plus,premium)compared to only needing two products for blenders.