There are hundreds of posts
at this and other Dodge forums
where owners want their engines to
"breathe better"
or
"work less hard"

There is a way to do this.

The way is to shift up to a gear where the rpm drops and the throttle opens up more.

This is why overdrive type gears are now on nearly all vehicles.

Why do Cummins Rams get better MPG ?

There are 4 main reasons:
1. these engines are not being 'strangled' by throttles
2. these engines have higher compression ratios and expansion ratios
3. these engine run at lower rpms where internal friction is less
4. diesel fuel has slightly more energy in each gallon

You can make your gasoline engine more like a diesel engine by opening the throttle and reducing the rpm.

Another way of saying this is:
Find a way to get your engine to operate at a higher "operating" torque and generally you will have higher fuel economy.

Here we are not talking about the 'maximum' torque you see on a specification sheet or dyno graph, we are talking about the torque that you the operator are allowing the engine to produce by how much you are pressing the pedal.

If want to remember key ideas about any type of engine,
remember these two short phrases:

"Its all about Torque"

"Friction never fails to pick your pocket"

Can you drop an engine too low in rpm?

Yes....for 2 main reasons

As an enthusiast you may have memorized that your Dodge engine has 8.9 or 9.1 or 9.6 compression ratio. This is the 'static compression ratio' and unfortunately it does not tell you the whole story. Because the intake valve does not close until after the bottom of the piston's stroke your engine does not get its full compression ratio and some gas can leak out backwards (reversion). Because the exhaust valve opens before bottom dead center, you also don't get the full expansion ratio. The actual compression ratio taking into account how the valves work is called the dynamic compression ratio. This dynamic compression ratio varies with rpm and gets worse at both low and high rpm. Engines that have 'variable valve timing' have a way to combat this problem and have higher torque and fuel economy at the low/high rpms.

The second thing that can happen at very low rpm is that each power stroke takes a longer amount of time. Why is the time of the power stroke important? Because if there is more time more heat can conduct out of the gases into the metal engine parts. Lost heat from power stroke = lost fuel economy. In addition to the heat loss, there can also be more gas pressure that leaks past the piston rings...which also reduces fuel economy.

How low is too low an rpm?

Well, it is not rpm that tells you what is important.
The key item is how fast the piston is moving up and down in feet per minute. To find this out you need to know the stroke of the piston.
A big diesel in a ship moving at 98 rpm and a tiny engine in a weed wacker running at 8,000 rpm can have their pistons moving at the same speed !
When piston speed gets below about 600 feet per minute things are getting too slow. When piston speed gets above 1600 feet per minutes things are getting too fast for good fuel economy.

Want to learn more?
It takes work...just like the designers of your Dodge truck had to work to get the knowledge that their fathers, grandfathers and great-grandfathers left them as an invaluable gift.

The USA would be a nation of slaves if this knowledge had not been passed on. The USA will become a nation of slaves if it is not passed on in the future.

You can either read the 682 pages of the Bosch Automotive Handbook,
or you can start by reading this 20 page long post:

https://dodgeforum.com/m_447500/tm.htm

 

yeah i am averaging 11 mpg in my 5.9L lol 20 bucks got me around town yesterday lol i think i might have bought a expensive dd

 

I did this and I've picked up an additional 1.5mpg on average. Who said that you guys were good for nothing?

 

Well it might have been our children.They ask for money to be good now a days. I remember when I was there age I was Good For Nothing!
That might have been it.