O/D off mode

[jhiles]

What do you guys think it means that I get better gas mileage when i turn o/d off? do i have a transmission problem?

 

[SWLathrop]

I assume your talking about an Explorer, but we need more info...

1. What year vehicle?
2. A 2 or 4 Door?
3. 4X2 or 4X4?
4. What engine (4.0 OHV, 4.0 SOHC, 5.0 OHV or 4.6 SOHC)?
5. What tranny (4 or 5 speed auto)?
6. A/C on or off?
7. City, Highway, uphill, downhill or flatland driving?
8. Driving like "Miss Daisy", or "Gone in 60 Seconds"?
9. How many miles on the odomoter?
10. Current and Up-To-Date maintainence or "Rode Hard and Put Away Wet"?

All this type of info helps in diagnosing problems. The more info the better.

 

[jhiles]

98 2door 4x4 sohc 5speed ac off
highway half mountains half flat
i do pretty much 80 most of the time on the highway
about 70k miles
always has oil changes at 3k miles
tranny fluid changed last year

 

[DeagleDave]

well leave the OD off around town and only use it on the highway. keeps your tranny from hunting between gears which will save your gas mileage.

 

[jhiles]

what i'm trying to say is i've driven this same 350 mile trip many times, and when i turned the o/d off i got probably 50 more miles per tank.

 

[DeagleDave]

do you drive the same way? like lead foot or easy does it? i would imagine it's got to get better gas mileage in OD because OD lowers your rpms which should increase gas mileage at a constant speed over a prolonged distance.

 

[jhiles]

i drive the same way every time.

 

[Jason_25]

Your keeping the engine in it's powerband, that's all. Evem if it's at a higher rpm, it is probably running more efficiently at that speed.

 

[Alec]

I agree, the overdrive gear lowers RPM by having a .78?:1 ratio as opposed to the 1:1 ratio of third gear. Lower RPMs aren't always best. If the RPMs are too low, the engine might not be as efficient. Each engine has a "sweet spot" RPM range where it's most efficient for a certain load.

 

[DeagleDave]

my engine doesn't have a sweet spot, it's pretty much all crap...hehe

 

[jssong]

lol.. i remember saleenexp sayin the 5.0 sweet spot was between 2500-4000. anyone confirm this? or have any other suggestions?

 

[MeatyCrab]

can you find the "sweet spot" using an air/fuel ratio meter?

is stoich gonna give you the most efficiency?

cheers,
BK

 

[Alec]

No. Your engine should always be close to or at stoich unless you're at WOT or coasting. It actually fluctuates between the upper and lower limits of stoich every second or so.

Basically your engine is best in the RPM range where you have most of your torque and also start building good hp.

 

[SWLathrop]

For my 97 and 01 Sports with the SOHC, I've found that anything above 2800 RPMs is best. I believe 3000 RPMs is peak torque for the SOHC.

 

[Majisto]

Originally posted by SWLathrop
For my 97 and 01 Sports with the SOHC, I've found that anything above 2800 RPMs is best. I believe 3000 RPMs is peak torque for the SOHC.

3200 RPMs I think actually, but yeah I usually let the SOHC go upto about 3K on normal acceleration or so. It gets up there pretty quickly if you're not careful A little too much throttle and that SOHC takes off.