Fuel economy question

[femurphy77]

I've now noticed this issue for the past 3 years and have decided it isn't a fluke or bad memory on my part; in the fall when the outside air temps start to drop my fuel economy drops almost 1 mpg. In the spring when it starts to warm up again my fuel economy improves and I regain that lost mpg. I've noticed this occuring when the temps drop below 50 degrees in the fall and when they start staying above 50 degrees in the spring.

I do nothing different other than add anti-gel, I don't idle it in the morning before driving it, my driving habits and traffic patterns don't change. The only difference I can come up with is the temp changes.

What gives? Anybody else notice this?

 

[JRJ04]

What is more than likely happening is the blend of fuel is changing from summer to winter blend in the fall and vice versa in the spring. the summer blend has a higher cetane rating and will yield better fuel efficiency, while the opposite is true for the winter.

It is not at all uncommon to see a few mpg change when this happens.

 

[DaveBen]

Yes, Winter Fuel does this. It will go back up when we get summer fuel. They blend winter fuel to lower the gelling point. It has less calories than Summer fuel.

Dave

 

[femurphy77]

I knew they had different blends but am surprised it makes this big of a difference. I've never had a vehicle that was as sensitive to this before I guess. Thanks!

 

[DaveBen]

Diesels do make a difference. I see about 2 mpg difference. If you are seeing more than this you might have to do some more checking. I think I would wait until summer fuel is here. I am sorry but I don't know when they change the blend.

Dave

 

[JRJ04]

correct me if i'm wrong, but I think it changes to winter around october time, and back to summer around the april-may timeframe

 

[Dogman]

When I drove tankers trucks it was around the end of april before we could start loading summer blends into the trucks for the stations. Winter blends was around oct to nov.

 

[Yooper75]

I normally do not see much of a difference but I treat my fuel all winter long with the PS white bottle treatement. I am consistently getting 15.8 all winter on the highway and 12.5 in town and I have also stopped treating my fuel already and have not noticed any change. How my idling is your truck doing because I notice a huge change if my truck idles a lot especialy in below zero weather when it's on high idle to warm it up.

 

[femurphy77]

I've only idled it long enough for it to hit high idle one time. My cold weather mpg is usally right around 15.5-15.6, my warm weather mpg usually runs up to about 16.7-8. Those are my combined numbers which are pretty evenly split city/highway although my city driving sees a LOT of stop and go traffic. I've never checked my highway only mileage but based on my combined would think that 17 plus should be doable. I'll found out later this summer though. If I can afford it! We're at $4.29/gal today here in central Indiana.

 

[Stroked68]

I think we are back to summer blends here cause I usually get around 14 to 15mpg with my 7.3 in the winter and I just did my mpg again yesterday and I got 18. Im happy with that!