my new '08 Automatic gets into 6th gear in town around 40 miles an hour lugging the engine at 1200 RPMs,that can not be good for it, or can these new generation engines handle it.

 

It probably does not meet the true definition from Cummins for lugging.

I can't quote it exactly but lugging is basically full throttle operation for more than a certain period of time while engine rpm is below torque peak.

I am certain you're not using full throttle in 6th at 40 mph. If you went to full throttle the transmission would downshift and raise rpm.

 

I don't own an 08 auto yet, but when I do, I'll run around town in 3rd or 4th, just like a stick shift.

 

That is what I have been doing,but if the engine can take running around town just above idle ,it has to be good for mileage.

 

Not necessarily, at least with my old stick shift.

 

My 07.5 pretty much shifts the same way. I cruise around town in 6th at low RPM and very little throttle. Give a little pedal and the RPM picks up. give it more throttle and it'll down shift. I would think the low RPM and light throttle would be good for MPG and not hurt anything.

 

Doesent the engine put out its max torque at about 1500 rpm o9r less? I think the engine is made to run that low of an rpm without any problems.

 

your correct they are.as with the big rigs I drive we lugg the SHNIZZLE outta them pulling 16percent grade up here at 1100 rpms and up, never any troubles also get better mpg with lower rpms.
run the truck around at lower rpms will give you better mpgs for sure also extend life of the engine.
REmember
there diesels there meant to pull and thats because there Tourqe is so low in the rpms, so use it.

 

Lugging is really an obsolete term. It referred to running the engine at maximum throttle below the torque peak when it could not gain speed. Under those conditions, many mechanical injection pumps would over-fuel under those conditions and pound the rod bearings out.

Modern electronically regulated pumps will not overfuel. Hence, lugging is impossible to do on a stock engine.

 

That is what I do. I traveled out of town the last few days and have seen two tanks over 16mpg's, with mixed (70% highway) running 70-75 on the interstate part of the trip. Rolled 3850mi today, it will be a month old tomorrow. I really like this pickup, it has far exceeded my expectations.