Fuel Mileage - Automatic vs. Manual

Well mpg depends on the driver, gross weight, and terrain. If all was equal i still say its hard to beat a good, smooth operator. I never used a big truck automatic so personally can't compare. But..for me standard is the way, as all in all i think much less trouble mechanically. I have witnessed 1 million mile transmissions. There again a % of that was the driver operating it. I am not against automatics, may even own one someday? I believe megas like automatics to eliminate chances on damage to the driveline. As probably most of their new drivers have trouble with a manual.

 

You may get better mileage with an auto, but it only takes one electrical gremlin and you're stuck somewhere, also from the little I've heard and read they're more expensive to replace eventually when you need to.

 

Ive heard that some automated manuals are very expensive to replace... Some to the tune of $25k

 

The Detroit DT-12 auto shift has Ecoast. Mode. It will go into natural and coast when possible. It shift at the correct RPMs every time. So save a little fuel doing that. I think the biggest saving is, it's a direct drive transmission.

It has some extra stuff like GPS location on the hills. So I change the shift point if going up hill. The transmission and engine talk to each other. The engine can turn on the Jake brakes between grease. So it never miss a grear when pulling a hill. When your at a stop line the computers will keep the brak pressure applied. Untill the truck starts to pull, so you don't roll back

For fuel mileage you spec the entire truck for that. The direct drive transmission and rear ends. So the engine RPMs at low going 65mph.. My new company truck has the Smart Park electric a/c for sleep. So no idle time on engine. It getting 8.4 MPG with super single tire. I'm really impressed with the setup. Truck has 8 batteries vs 4. The 4 extra run the A/C at night and something like 250 or 275 amp alternator. To recharge the batteries going done the road

 

I'm sure autos probably get a bit better fuel mileage but I still believe that manual is better for reliably but if you have a ####ty driver that cant shift it will not last as long

 

A good driver will beat an auto shift hands down.
However fleets cannot get very many good drivers so they purchase auto shifts to improve their odds.
I have an auto shift now, I’ll be going back to a manual next time.
My WesternStar 4900SF (not at all aerodynamic) got 0.2 better mpg than my Cascadia (aerodynamic) with an Eaton UltraShift.

 

Very good driver on a manual 18sp will beat out auto 18sp by a slim margin. Autos are easier to get then a good driver though

 

Thats a plenty of gadgets. The hand valve, or trolley brake ,whatever, is how we hold our truck on a hill as we let the clutch out. Lol. The fuel mpg is great. ( what, where, and how heavy)? Not a fan of super singles. Just about every time i pass a super single that is flat, the rim is ruined also. Not good $$ wise at least for me.

 

The DT12 is lights years ahead of the Eaton Ultra Snap POS. That transmission clunks every gear change and it sounds like it’s going to drop out of the truck.