If there is a thread that covers this already, please direct me to it.

I have read allot of stuff about winter vs summer mpg and the fuel. Everyone says that winter gas is worse and hurts mpg, I know mpg in the winter is worse, but don't fully understand why. Is it because the fuel mixtures are actually diff. or is it because the temp outside keeps the fuel colder and makes it harder to ignite so you use moreor easier to ignite so you use it faster therefore reducing mpg?

Thanks
Ron

 

sorry haha not trying to just send you links but they can explain things better than i can. here is a really interesting article i foudn about winter and summer gas.

http://www.slate.com/id/2098672/

 

I don't mind all the links, I am not too lazy to read. Thanks

 

Other than the blend in gas, how much would a posi rearend vs. the one spin wonder effect the milage. The rear in my truck is limited slip, very limited. in the air I can turn one wheel and the other spins the same direction. My cousin who works at a Dodge dealership as a mechanic said they had some limited slips that were real tight. Mine must be one. ut it's been that way since new.
Not complaining though.

 

 

A posi does not affect fuel economy one bit (compared with an open differential of the same ratio).

A posi axle is supposed to do how yours does (both tires spin in the same direction). If the tires spin in opposite directions when both are off the ground (and the driveshaft is free to rotate), it's either not a posi or the posi unit is blown. If you put your truck in gear and try the same trick (jack up the axle with both tires off the ground), you should NOT be able to rotate either tire...or it should be very difficult, because you'll FORCE the other side to spin "backwards", and it'll be doing so against the posi mechanism.

Edit: if your question is getting to how the posi creates resistance around corners, and does that negatively affect fuel economy...I suppose you could argue that in theory, but I've never seen any empirical data that showed that it did.

 

Soundslogical, but what about rolling resistance? The truck turning both rear wheels at the same time vs. power to push one? Would that have much effect?
Just thinking...

 

As long as neither tire is slipping, the drive shaft IS driving both tires. There is no difference here from an open differential. The difference is when one tire starts to spin. In an open differential, that tire becomes the path of least resistance, and that tire will begin to spin faster than the other, and forward traction is lost. In a posi differential, clutches in the unit engage (depending on how the unit is designed), keeping that tire from spinning faster than the other, and maintaining your forward traction through the other side of the axle.

In theory, there is more resistance when turning a corner because of that clutch action in a posi differential, but again, I think the difference in fuel economy would not be measurable.

 

sounds logical.