Winter Blend

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68PowerWagon

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Well the dreaded winter blend has been out for a few weeks now! This vehicle responds to this the worse than any other vehicle I have owned. Drops about 3-4mpg. Most of my other vehicles were more like 1-2.
Anybody know what they change in the formula that makes it do this?
 

2015HD

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From AAA website:

The difference between summer- and winter-blend gasoline involves the Reid Vapor Pressure (RVP) of the fuel. RVP is a measure of how easily the fuel evaporates at a given temperature. The more volatile a gasoline (higher RVP), the easier it evaporates.

Winter-blend fuel has a higher RVP because the fuel must be able to evaporate at low temperatures for the engine to operate properly, especially when the engine is cold. If the RVP is too low on a frigid day, the vehicle will be hard to start and once started, will run rough.

Summer-blend gasoline has a lower RVP to prevent excessive evaporation when outside temperatures rise. Reducing the volatility of summer gas decreases emissions that can contribute to unhealthy ozone and smog levels. A lower RVP also helps prevent drivability problems such as vapor lock on hot days, especially in older vehicles.
 

wgreggking

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They add butane in the winter to make it evaporate faster at lower temps. The octane is supposed to stay the same. It also varies by region as to when it changes.
 
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68PowerWagon

68PowerWagon

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Interesting... I figured it was something along those lines. 10 years ago or so I thought it was just fuel injected engines would run rich in the winter like a partially closed choke on a carbureted engine. Later was told it was the fuel.
It is a 2016 with about 22,000 on it. I don't know if it took this long to brake in but this summer I was getting much better mpg prior to the first year. According to the lie-o-meter I was getting 16-18 driving back & forth to work. Scored 15.4 mpg on a long trip pulling a 4,200lb. boat plus about another 1,000 in luggage & people. Haven't done much hand calculations but the ones I did, meter was off by about 1-2mpg. Not too bad for as heavy of a pig as she is! :roflsquared:
 

SouthTexan

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A copy and paste from one of my previous posts on this same topic from January.

For gasoline, it is summer blend fuels that have additives to help the environment by lowering its RVP making it less volatile at higher temperatures, not winter. Summer fuel has about a 2% higher energy content due to these additives which is one of the many reasons why you get better fuel mileage in the summer. Winter fuel does not have these additives so it has a higher RVP which increases it's volatility so it can be easily burned in colder temperatures. You would have a lot harder time starting a vehicle with summer fuel on a very cold day than you would with winter fuel. It would also run rough.

There are other things that decrease your mileage during the winter as well like lower tire pressure and the air being more dense. For every 10 F the outside air drops, your tire psi will drop about 1 psi. So if it was 35 psi at 100 F, then it is 25 psi at 0 F. Colder air is also more dense than warm air which means you have to apply more load on your engine in order to push through it. The research we did at Cummins showed a 2% increase in aerodynamic drag for every 10 F decrease in temp.

Also, for gasoline engines, colder more dense air will cause the engine to burn more fuel to stay at the optimum 14.7:1 stoichiometric air/fuel ratio. Basically 14.7 air to 1 fuel. Gasoline engines have to stay around this ratio at all times in order to run correctly and not damage the engine. Since colder air is more dense, there is more of it in a given space. Therefore the engine reads this from the MAF sensor and adds more fuel to compensate for that increased air density. If it didn't add more fuel then it will run lean which damages gasoline engines.

This is why intakes generally hurt fuel economy on newer gasoline engines since the MAF sensor will tell the ECM to add more fuel for any extra air added. This is not the case for diesels since they run lean just about all the time so intakes generally make them more efficient. Under load diesels run about 16:1 and at around 140:1 at idle.
 

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Yeah, winter blend makes my mileage take a hit, always lose couple of mpg at least. That and I am putting on new AT tires this week. Its gonna suck.
 

Will Ram 2500

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Ours must have just changed over plus we've been getting below freezing since Fri night. Filled up Fri afternoon. My display says low 11's right now when it's been in the 14's usually. Towing Sat with a 1000 lb tandem axle utility trailer with about to 2000 lb's in mowers and weed eaters it showed low 9's when it's usually in the 11's. Never had an engine affected this badly by cold temps and winter fuel.
 
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mohemipar

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Remember guys, all that matters is Smiles Per Gallon. :naughty:

Surprisingly I haven't noticed my truck showing any signs of dropping much yet. And I have been remote starting in the AM and letting it idle for 5-10 mins. Dropping below 30 at night now. That extra idling used to kill the computer calculated MPGs in my 1500.
 

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And I have been remote starting in the AM and letting it idle for 5-10 mins. Dropping below 30 at night now. That extra idling used to kill the computer calculated MPGs in my 1500.

Yup, haven't had to start that yet, but it kills mine. But warm wife=good day....:roflsquared:
 

MN-Ram

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I was wondering about that. My mileage went down by about 2 MPG’s in the last week.
 

loveracing1988

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Interesting... I figured it was something along those lines. 10 years ago or so I thought it was just fuel injected engines would run rich in the winter like a partially closed choke on a carbureted engine. Later was told it was the fuel.

Well the dense cold air you get in winter doesn't help because it dumps extra fuel to compensate for the extra air.

I don't know when exactly we switch in Michigan, but I lost 1.5 mpg's right after hurricane Harvey went through, I don't know if it was a coincidence or not, but i was getting 14 3 tanks in a row and then suddenly haven't gotten above 12.6 since.

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King nothing

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I just bought my truck a week and a half ago and I REALLY hope we already have winter blend and my mileage doesn’t get worse. Last tank hand calc at 12mpg and that was 90% highway running 75. Hope it doesn’t get worse and it would be nice to pick up a few MPG in the spring


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