Summer Blend to Winter Blend Change Over

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SubLGT

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When gas stations have winter blend gasoline delivered, is there a regulation that limits how much the winter blend can be diluted by old summer blend fuel still in the storage tank?

For instance, if I buy a tank full of premium gas in the middle of October, will it be 100% winter blend? 50% winter blend? Something in between?
 
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you actually "feel" the difference?

I don't. All I can tell by the time they switched over to winter blend is the time I see fuel economy variations...no difference in budt-dyno.

Q.
 
Originally Posted By: Quest
you actually "feel" the difference?

I don't. All I can tell by the time they switched over to winter blend is the time I see fuel economy variations...no difference in budt-dyno.

Q.


I can in my Cherokee. It has two catalysts under the fuel injectors. With "summer" fuel, it will occasionally get a cylinder 3 misfire from having fuel boil in the injector. With winter blend fuel, it will start having random misfires on all cylinders after idling or sitting for 10 minutes or so.
 
Originally Posted By: Quest
you actually "feel" the difference?


Yep. In warmer weather, I can't really tell the difference, but once it gets down around freezing or colder, it's very obvious. With winter blend, the Jeep starts like it does in the middle of summer (right down to sub-zero temperatures). At 25* with summer blend in the tank, it cranks for 5 - 7 seconds before it fires at all, and then it takes another second or so after it lights off before it hits on all 8. The summer blend fuel just doesn't vaporize easily enough in a cold engine at low temps.
 
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Originally Posted By: Quest
you actually "feel" the difference? ..


The blend % affects fuel vapor pressure, and that can affect how easily the engine starts in cold weather.
 
Back to your original question. I asked a tanker driver and he said that he just fills the tanks and that's that. What ever the mix might be on the first tank at change over is whatever it happens to be. No one bothers with such details.
 
Originally Posted By: SubLGT
Originally Posted By: Quest
you actually "feel" the difference? ..


The blend % affects fuel vapor pressure, and that can affect how easily the engine starts in cold weather.
Perhaps with a carburetor, with fuel injection not so much. The main purpose of "winter fuel" is to allow refineries to sell cheaper butane laced gasoline.
 
I may be wrong, but I doubt that RVP matters in ease of starting to a degree that you'd notice.
Summer blend fuel is no more than winter blend fuel with reduced RVP, intended to reduce evaporative emissions during the warmer months and is an EPA mandate, not an industry initiative.
I suspect that any engine would start and run just fine on either blend of fuel during any season and that winter blend fuel is more something that blenders are allowed to produce to use up the more volatile, cheaper fractions than anything really needed for winter starts.
Even summer blend is plenty volatile stuff and people run piston aircraft all year long on a less volatile fuel than summer blend mogas.
I've had occasions where we've had a car full of summer blend fuel sit into the winter before being run again.
Guess how hard it wasn't to start?
 
There are maps out there of RVP minimums and maximums. There's usually a no-mans-land in Spring and Fall where anything goes, to give time for the legal stuff to make it to the end user. If you find a map you can find your jurisdictions and any peculiarities.

I get best mileage in March-April from the "whatever" blend

It would look kinda like this; I can't vouch for the date of the file but it's titled "summer gas".

20110428124133summergas.jpg
 
Originally Posted By: fdcg27
...I suspect that any engine would start and run just fine on either blend of fuel during any season...


Have you (or anyone else here) had any experience starting a snowblower at say, 25 degF, with low RVP summer fuel in it? I would expect that to be harder to start. Just curious.
 
Use up my old lawnmower gas in my snowblower every year. Gas bought in August and used in November or December, temps as cold as zero, with no problems. Year after year.

Reality is the tanker driver never needs to think about it, and neither do the stations. The distributors start changing over well before the change in seasons. Here, the start occurs in September, and is into full bore winter gas by November. Changeover back to summer starts occuring by Mid -february and is done by May 1.
 
Originally Posted By: OneEyeJack
Back to your original question. I asked a tanker driver and he said that he just fills the tanks and that's that. What ever the mix might be on the first tank at change over is whatever it happens to be. No one bothers with such details.


Even in California, with their strict limits on summer fuel volatility? I would have thought that CA regulators would not want the summer fuel to be "contaminated" with winter blend.
 
That is why the pipelines / distribution companies etc actually usually require an RVP that is lower than the legal requirement - at least with the early stuff. They assume it will be blended with whatever is in the tank at the gas station. Put enough of the new blend in early enough, it ends up not mattering.
 
There's no practical way of avoiding this and even EPA and CARB recognize that.
A tanker load of fuel doesn't last very long at a typical station.
The old winter blend high RVP gas gets diluted out of existence in no more than a week.
 
Originally Posted By: fdcg27
...A tanker load of fuel doesn't last very long at a typical station...


Premium fuel is not as popular as regular, I wonder how long it sits in the storage tank underground.
 
Originally Posted By: OneEyeJack
Back to your original question. I asked a tanker driver and he said that he just fills the tanks and that's that. What ever the mix might be on the first tank at change over is whatever it happens to be. No one bothers with such details.


Unless you post here at BITOG LOL

There is NO WAY they are sucking any left over gas out of the ground at switch-over time. They just fill the tank and move on. There is a blend period, probably early enuff in the season that it makes no difference.....unless again we visit such places as BITOG HAHA
 
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