Cold temp short commute option - nix the OD?

[ProfPS]

Having read and responded to oil related posts regarding short commutes in cold weather and not driving long enough to effectively warmup the engine and oil to remove moisture and bring the engine to its operating temp for the computer to back-off a rich air/fuel mix, what do you think about not putting the car in overdrive?

Driving 1 gear lower than OD will run the engine at a higher RPM but not significantly higher and far from the red zone. Higher RPMs will warm up the engine and oil, and produce a higher exhaust pressure to blow out more exhaust system moisture than normally. Only down side is that MPG's might be down depending on the driving conditions.

In my Rav4 today at 40 mph (4.5 mi commute), it was the difference between 1400 RPMs in 5th vs 2000 RPMs in 4th with less trans shifting while driving in my hilly area.

 

[98LSC32V]

You should always drive with the overdrive off in the city but not for the reason you are suggesting.

 

[mechtech2]

Leave it in OD. Fuel benefits would be #1.
The exact same load is on the engine either way - the requirements are the same.
If the drive is too short to get it up to temp, a little fudging won't help.

 

[SFCP]

Originally Posted By: ProfPS
Having read and responded to oil related posts regarding short commutes in cold weather and not driving long enough to effectively warmup the engine and oil to remove moisture and bring the engine to its operating temp for the computer to back-off a rich air/fuel mix, what do you think about not putting the car in overdrive?

Driving 1 gear lower than OD will run the engine at a higher RPM but not significantly higher and far from the red zone. Higher RPMs will warm up the engine and oil, and produce a higher exhaust pressure to blow out more exhaust system moisture than normally. Only down side is that MPG's might be down depending on the driving conditions.

In my Rav4 today at 40 mph (4.5 mi commute), it was the difference between 1400 RPMs in 5th vs 2000 RPMs in 4th with less trans shifting while driving in my hilly area.


sam1?

 

[Curious Kid]

Originally Posted By: 98LSC32V
You should always drive with the overdrive off in the city but not for the reason you are suggesting.


What might the reason(s) be?

If a manual transmission I could see the concern for potential lugging of the engine, and the delay in possible accident avoidance with the power loss/shift delay.

 

[UncleRunkle]

My jag never gets to 5th in my short commute any way...

 

[byez]

I was thinking about this today as well. At 60 km/hour the difference between overdrive-off and overdrive-on my vehicle is 2000 rpm vs. 1500 rpm, nothing major. I think that I just may turn overdrive off if I know that I will be making short trips. Any increased transmission wear from this practice?

 

[ProfPS]

I don't see any increased trans wear by not putting an auto or manual trans in OD when driving at speeds < 45 mph. If anything, there will be less wear due to less shifting in and out of the OD gear.

 

[cfromc]

I doubt if it would make any appreciable difference by leaving it in "D" and not "O", in regards to the oil. You may lose some gas mileage and put some additional insignifant wear on the engine, but otherwise, nothing. I don't think it would allow you to lengthen your OCI.

 

[rangerdood]

Overdrive is for highway use. If you're in town, leave it off, and you'll spare your transmission and torque converter a lot of wear.

 

[yota4me]

A Scan Guage would indicate which provides better fuel economy. Otherwise, I'd think you'd get best fuel economy staying within manufacturer's recommended shift/gear/speed recommendations.

 

[byez]

If overdrive should be always off why is my car automatically defaulted to overdrive every time i start my car? I have to press an "overdrive off" button at which point a warning light on my dash is activated.

You are saying the manufacturer made it so that the consumer has to turn overdrive off whenever driving in town by pressing a button?

 

[BuickGN]

It's a trade off. With OD off, load is lower and rpms are higher. I have watched this many times with my GN in the form of injector pulse width. At a steady state cruise, the PW will be less in a lower gear but the injector is firing more often. Most of the time your best fuel economy will be with more load in the taller OD gear.

For driving around town with OD off, it does a couple things. It's less shifts the trans has to make. The greater the difference between the engine speed and input shaft speed, the more heat is going to be generated by the torque convertor. Only problem with that is sometimes the TCC doesn't engage or engages at a higher speed as part of the strategy with OD off which will make more heat.

 

[ProfPS]

With that said [and related to my original post], when having a short commute in cold temps - by not shifting into OD will heat the engine, trans and exhaust faster than allowing the trans to shift into OD. I see a short commute being < 6 mi with speed < 45 mph.

 

[Drew2000]

FWIW...on my Expedition, the computer will not allow a shift into OD until the engine warms a bit and starts moving the temp. gauge in cold weather. Probably to warm the cats quicker to reduce emmissions.

Drew

 

[BarkerMan]

You might want to consider keeping your engine at around 2k rpm when cold, picking a gear that will do that. You engine will lubricate a little bet better. Those low engine speeds when the engine is cold can't be any good, and OD will put below 2k rpm if you let it. Also the low engine speed is not good for your transmission. It's cold too. The BMEP is higher at low engine speeds and that combined with cold oil is cause for xtra wear.

 

[road_rascal]

On my 6 mile commute to work I always have the OD off. Too many hills to deal with and I almost never hit 50mph, about 45mph for a 1 mile stretch. Most of the time it's 30-40mph.

 

[steven88]

I am in the same boat here...I drive a VERY short commute...about 2 miles in my 95 beater v6 camry...theres an OD switch I can use to cut off OD...it's got 175k miles on original engine and trans....would turning OD off reduce wear and tear overtime? I want to try and push this camry as far as it can before it dies...been keeping up with all the fluid changes and I'm just waiting till the day my engine or trans takes a dump

 

[steven88]

bump for some answers

 

[carlprop]

I like to keep my automatic out of overdrive in city driving myself. As others have noted, there is less constant shifting of gears. Also it helps somewhat in engine braking power coasting to a stop. Especially if you live in hilly terrain.