This probably has an obvious answer that I thought about and dismissed, but I felt the need to ask. How come when it's pretty cold outside (10-20 degrees) my truck feels like an absolute slug for the first 5-10 min of driving? I mean less power or acceleration than normal, even if I let the engine warm up before starting out. When the temps are warm out there's really no issue. The problem doesn't bother me, i mean the truck is almost 22 years old. It's just peculiar, and this is the first vehicle I've ever driven where this has happened.

My other question is one of personal curiosity. I was reading somewhere that cars are more efficient in general when they are driven in their powerband, any RPMs too low or too high will cause poor fuel mileage. I'm just curious as to which style of driving would get me the best fuel mileage around home.

Many of the roads around my house are winding country roads with occasional rolling hills and a 45mph speed limit. Now my truck is the 300/5spd combo with 4x4, 3.55 gears, and 31s and I used to run 45-50mph in 5th gear. This put my RPMs around 1500 and the truck would do it fine but it felt like I needed to give it more gas and it generally feels like the engine is working a bit harder at the lower rpms. Disclaimer though, I've never lugged the engine - even slowing down to 40 to go around curves I could still get into it and she'd slowly pick up speed again. Lately after reading this technical article I've tried something a little different. I started running her in 4th gear at 45mph rather than 5th. This puts my RPMs at just under 2000, which I read is where the 300 makes its max torque. Doing this I sacrificed extra speed but it feels like I have to use less throttle and it's definitely easier to slow up for curves or confront a small hill, and resume my normal cruising speed.

Can someone who's more technically adept with engine technology and trucks in general tell me if running in 4th with a faster spinning engine is more efficient than turning less RPMs in 5th? This is really just to satisfy my own personal curiosity more than anything else, I wanted to see if what I read is actually true. If so, how is an engine more efficient even though its spinning faster?

Thanks for helping me learn!

 

The sluggishness is likely the gear lube in the transmission and differentials are closer to being like grease until they warm up..

 

The sluggishness cold is most likely the Exhaust Back Pressure Valve (EBPV.) It closes when the engine is cold to help warm the engine. When it's closed there is a lot of exhaust backpressure, which robs power.

 

I had an '84 and an '86 that were the same way. I figured it was something that affected all 300's and I didn't worry about it.

However, I never shifted mine into OD till I could maintain a constant 50+ MPH. Too much peddle work for my liking and the trucks with the 300's were very doggy but incredibly reliable. The reliability is the only reason why I went back for a second one.