Temperature and Mileage?

[bigbossman26]

Here's an interesting thing that happened to me yesterday. Took a 250 mile trip return. Started out with fuel to the cap and left travelling @ 60 mph. Temperature outside was 30 C or 86 F outside. Truck temp was below 195* not a problem. Filled up to the cap again at destination and calculated MPG got 22. Drove back same route last evening with temp outside down to 18 C or 64 F late at night and filled up to the cap when I got back in calculated MPG and got 26??? Strange but the only thing different with the trip was temp and humidity outside, think I need to travel when it's cooler to get optimal MPG. Any thoughts?????:confused:

[Subzilla]

Yes, cold air does increase power and mileage although I've never experienced THAT much of an increase. Cold, dry air is more dense (less atom movement) and our diesels like that - hence the principal behind turbos and intercoolers. The turbos compact the air and the intercoolers, of course, cool that heated air back down giving the engine more air molecules per diesel fuel molecule - more power. In the cold of winter, once I get my old 6.2 started and warmed, it tends to run much smoother and crisper than on these hot, muggy summer days. It really acts like a dog then. Some of these other guys will chime in here with the thermodynamic equations and such. I left most of that knowledge back in college!