My MPG results- 3rd vs. D (1991 Q)

[DR.Q]

15.36 gallons driving 99% city streets in 3rd got me 225 miles = 14.65 mpg.

13.82 gallons driving 99% city streets in Drive got me 200 miles. = 14.47 mpg.

Same steets. Certainly there is a margin for error by eyeballing the gauge. But I'm as good at it as anyone because I live below E. Not quite what I expected. I guess I'll go back to driving exclusively in 3rd in the city.

Stephen

[Q45tech]

Obviously a definition of CITY driving would vary as every minute/second above 45 mph would be better in 4th gear but most Q engines are less than stellar at [45 x 33.3= 1485 rpm] bucking and snorting especially on hills and with AC on creating a downshift anyway!

With 4 gears the gear spreads are just never right for every situation:[0.555,0.649, 0.694] and a total spread of [4.00 from 1333/333].

Most would see the same CITY situation [in other similar vehicles] as the top gear [in a 4, 5, 6 speed transmission] is pretty much fixed based on weight and engine design and displacement. Notice every 32 valve 4,000 pound luxo-sport turns 2000 rpm at 60 mph............some of the newer 6-7 speed AT designs have 2 overdrives to account for a cruise of 70-80 mph to reduce rpms another 15% but this won't work at 50-60 mph.

[louiegz]

I did it once and I lost a MPG doing the 3rd gear thing. I just leave it in D and downshift when I get to a hill.

[Q45tech]

Isn't that what an automatic does anyway, select the most appropriate gear based on engine load and speed.The question is gasoline mileage vs transmission reliability [life].

80 gallons per year more fuel ~~ $160-$200 [10% lower mpg WORST CASE] vs the $3,000 increment for transmission replacement.

Not sure if using the extra fuel say $1000 in 5 years would defer the transmission failure by 5 years since 11 years of transmission life is a long time regardless of mileage accumulation!

I don't understand why people don't save $300 per year in a transmission saving account or $1000 for a general repair account over and above the $1500 maintenance expense.

Not doing so gives you a false sense of what it cost per year to drive.

[maxnix]

I agree with Q45tech, and Dr. Q. My mileage in 3 around town is the same or better than with the transmission in D. I don't use D unless I am at cruising speed on the level on a freeway, or on a long down grade. Being in 3 while merging saves a down shift and gives the car a little more flexibility to position itself in the traffic flow.

My mileage seems to hover around 15-17 mpg, depending on season and whether it is 70%-30% freeway to city ratio or the reverse.

[Rex]

I have to ask, do you bump the car into D as you approach a stop?

I understand the logic of fewer ****s, but I would think the transmission doing "some" of the braking is also wear on the transmission itself.

Thoughts?

[DR.Q]

My results reflect very rarely going over 45 mph. Speed limits are pretty much equally 25, 30, 35 and 40 where I drive. And I am certainly not one to speed...............that much.

[maxnix]

I have to ask, do you bump the car into D as you approach a stop?

I understand the logic of fewer shifts, but I would think the transmission doing "some" of the braking is also wear on the transmission itself.

Thoughts?

Almost never, unless it is a prolonged coast. Engine braking under coasting would be minimal unless it was a steep downslope, then I shift into D.

[elwesso]

how would that make any difference..... If ANYTHING it causes more wear on the engine due to higher RPM.....

The transmission is still turning, its just in a different gear..... Then again, its as flat as a board here so hills mean big bumps...

But I agree, my MPG is always the same (or better) by driving in 3... I am ALWAYS in 3 until I stay about 40mph for a long time..... Ive found that getting lucky and getting good gas gets me better mileage than gears...

Also, not going into the latter half of the tach helps too!!!

[Jeff Williams]

i keep my car in lower gears, to save the transmission from "chugging". I usually shift through all 4 gears, manually, at normal RPM's )it is fun to use the shifter). I also bump the car into Neutral at most red lights, to save the transmission from heating up needlessly. If I can, I'll bump the car into neutral, and coast to the stopped traffic. I always bump it into neutral at drive-thru's, down hills, on the interstate sometimes, and in stop-and-go traffic. I coast about 2 to 3 miles everyday, on my daily commute of 138 miles.

I use the motor to slow the car down, on steep hills, to save brakes.

I try to use 3rd as much as possible, but the car still hesitates, and jerks where it usually shifts into 4th, so I usually shift into 4th or slow down a bit.

My brakes still only last about 20,000 to 30,000 miles, my transmission will probably only last about 150,000 miles (it is at 105,000 right now - second one), and my gas mileage is about the same, no matter what I do, as long as I dont drive it like a Mustang.

I agree with Dennis, on longetivity of transmission, tires, and brakes are more important than gas mileage.In the long run, you just can't save enough gas, to make up the difference.

[elwesso]

Jeff... To me your last statement and first statement seem to contradict each other...

With a transmission cooler, you shouldnt need to worry about it heating up.. IMHO.. Also, the less shifts the better, right?? Shifting in/out of neutral, IMHO is bad...

[Q45tech]

The transmission is tested and rated for 100,000 shift cycles [severe medium dyno loads] not WOT loads say half throttle. Every shift cost you money. ABOUT: 1- 3 cents per shift cycle..............just put that dollar a day in a cup every morning from the first day you pick up the brand new car and and 10 years later you'll have plenty.