to Drive or to Overdrive?

[omega_rugal]

i have seen many cars with 4 speed trannies non-OD trannies perform better than their 5 speed OD counterparts, my 97 Sable returns 1-2 more mpgs in D as long i don't drive faster than 45 mph due the TC locking up faster and staying that way, i also can pass other cars faster due not having to downshift every time i floor it... my older carbed 93 Tsuru , 4 speed transaxle was more efficient than my mother´s newer, fuel inyected, 5 speed tsuru, running both cars at the same time, with full tanks and the refilling after reaching our destination mine got around 5% better economy, confirmed real world test.

 

if OD it´s supposed to boost fuel consumption, engine wear, drive train wear and so on and so forth why i´m getting better results with D than in OD? my guess is that in D frictional losses are lower, that combined with the taller ratios that non OD usually have puts the engine in a more efficient range, and in my sable´s case, locking the torque converter earlier (the ax4s shift programming sucks @$$, who made this thing?)

 

i´m bored right now so bear with me...

[Pete M]

mpgs are a very complicated math problem.  

[omega_rugal]

it is, it limits the fun i can have in my MJ and how much can go on upgrades instead of fuel 

[Eagle]

The problem is that Jeep selected the gear ratios for performance in emissions and gas mileage tests prescribed by the government -- which were run on a chassis dynomometer, not on the road. So there was no wind resistance factored in. I've found that my 88 4.0L 5-speed gets equal or better fuel mileage in 4th gear as in 5th. In 5th, at 55 or 60 MPH, the RPMs are well below the engine's torque peak, and running at or close to the torque peak is the most efficient cruise setting for an engine. I think 3.55s or 3.73s are a much better gear choice for the 5-speed, and 3.73s should work well with the AW4 as well.

[omega_rugal]

4 hours ago, Eagle said:

on a dynomometer, not on the road

 

the goverment rearing its ugly head again...