Best MPG : 5-speed vs. auto?
 

Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
Toyota, which would
get better MPG -- one with automatic tranny or 5-speed?

I understand that 5 speeds vs. 4 gives a better selection of rpms,
meaning at the same speed you can cruise with lower rpms, assuming the
same rear axle ratio.

Also I understand that 5-speeds don't have a torque converter that
autos have which robbs some power.

But in my experience, in city driving, it's hard to shift well for good
MPG. Maybe I am shifting at wrong rpms, I am not sure.

Best MPG : 5-speed vs. auto?
 

SQ wrote:
>
> Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
> Toyota, which would
> get better MPG -- one with automatic tranny or 5-speed?
>
> I understand that 5 speeds vs. 4 gives a better selection of rpms,
> meaning at the same speed you can cruise with lower rpms, assuming the
> same rear axle ratio.
>
> Also I understand that 5-speeds don't have a torque converter that
> autos have which robbs some power.
>
> But in my experience, in city driving, it's hard to shift well for good
> MPG. Maybe I am shifting at wrong rpms, I am not sure.

Automatics will always have some loss due to the torque convertor.
However, they tend to be equal to sticks because most drivers are not good
shifters.
If you want good mileage, then shift at the lowest rpm possible without lugging
and drive as slow as possible without getting shot.
I don't know you mean about "5-speeds don't have a torque converter".
Are you speaking of automatics, or sticks, or something bizarre like a
convertor-less double clutch automatic?

Best MPG : 5-speed vs. auto?
 

Well, this explains a lot. I have been driving a 5-speed and have been
getting awful mpg in city. Now I am realizing I am shifting at very
high rpms, around 2500. I will try to lower the rpms during shifting
and see if it makes any difference.

(I think one problem in my particular situation is that the type of
engine I have derives it's power from high rpms, you have to rev it to
get going, and I don't like it)

Best MPG : 5-speed vs. auto?
 

SQ wrote:
>
> Well, this explains a lot. I have been driving a 5-speed and have been
> getting awful mpg in city. Now I am realizing I am shifting at very
> high rpms, around 2500. I will try to lower the rpms during shifting
> and see if it makes any difference.
>
> (I think one problem in my particular situation is that the type of
> engine I have derives it's power from high rpms, you have to rev it to
> get going, and I don't like it)

Small overhead cam engines are like that. Especially ones with lots of valves per
cylinder. They develop max hp and torque near max rpm.

Best MPG : 5-speed vs. auto?
 

"SQ" > wrote in message
oups.com...
>
> Well, this explains a lot. I have been driving a 5-speed and have been
> getting awful mpg in city. Now I am realizing I am shifting at very
> high rpms, around 2500. I will try to lower the rpms during shifting
> and see if it makes any difference.
>
> (I think one problem in my particular situation is that the type of
> engine I have derives it's power from high rpms, you have to rev it to
> get going, and I don't like it)

As he said, the automatic should have a little more loss, but in fact they
get about
as good mileage as manuals for most drivers.

Drive as though you have a glass of water sitting on the dash. Hi revs
usually
waste fuel. Jump starts, race car tactics usually waste.

Best MPG : 5-speed vs. auto?
 

On 8 Apr 2006 15:32:49 -0700, "SQ" > wrote:

>
>Well, this explains a lot. I have been driving a 5-speed and have been
>getting awful mpg in city. Now I am realizing I am shifting at very
>high rpms, around 2500.

I can't think of anything other than a large diesel engine where 2500
rpm could be considered "high" let alone "very high." If its a 4 cyl
OHC engine its just barely entering the bottom of its power band at
2500. "Very high" rpms would be more in the range 0f 7000-8000. Many
modern totally stock 4 cyl. engines can handle that with no ill
effects whatsoever.

> I will try to lower the rpms during shifting
>and see if it makes any difference.
>
>(I think one problem in my particular situation is that the type of
>engine I have derives it's power from high rpms, you have to rev it to
>get going, and I don't like it)

Then you should buy an old Lincoln or 500 cubic inch Cadillac
Eldorado. Small engines all need to rev to produce power.

FWIW automatic transmissions free-wheel under various conditions which
helps offset their gas mileage reducing attributes. Its easy to see
this if you have a tach.

Don
www.donsautomotive.com

Best MPG : 5-speed vs. auto?
 

The subaru loses about 10% due to the 4wd ... so leave subaru out of
the identical cars. The 5-speed ... 5th is typically an overdrive and
wins hands down on the highway ... or, if you don't do much
highway/freeway driving, not much point. My '96 4.0L jeep Cherokee at
about 3100 lbs is a 4 spd auto (overdrive) with lock up torque
converter ... and consumes 10 litres/100km at a steady (cruise control
helps the mileage) 100 kph hour at about 1800 rpm ... and that's about
the same mileage as my subaru got ... at 3000 rpm. Driving in the city
I normally don't exceed 1800 rpm in any gear and the acceleration is
fine by me. There's always the guys in their little 4-cyls winding it
out between traffic lights ... sure it's fun ... but they don't need to
develop that full horsepower at high revs to move those little cars
from one light to the next. Got to admit though ... if I still had the
stick, I'd be winding it out too, and downshifting to brake.

Back to your post ... imo ... with todays engineering, and adding to
your equation equally skilled drivers ... mileage would be about the
same.

Best MPG : 5-speed vs. auto?
 

Oops ... subaru ... awd :-)

Best MPG : 5-speed vs. auto?
 

I'm rare. I don't mind city or gridlock traffic with a manual tranny.

I've been driving one for over 15 years and think I've got it down pat.
My current car is a Nissan SpecV with a QR25DE engine and 6-speed
tranny. The car's EPA rating is 23/29 and I've gotten over 30mpg on
some tankfuls. So, When I drive in a fair amount of low speed traffic,
my mileage still doesn't drop below 26-27mpg ... as long as I'm not
stopped for too long.

Basically, I drive in stop-and-go traffic close to idle RPM. With
modern engine management systems, the engine won't stall if you are
careful with your transitions. In gridlock, I'll idle in 1st gear as
long as there is room ahead of me. And when traffic starts to move
ahead of me, I get going ... but no jackrabbit starts. It's likely it
will slow down again a few hundred yards up the road, anyway.

In slow traffic during snowstorms, I have idled the car in 2nd and even
3rd gear for miles. Never touched the gas or the clutch. It's all
about thinking ahead and pacing yourself.

I work in a downtown area without a set parking spot/lot so I have
spent up to 35 minutes circling the blocks looking for parking. But
because I drive sensibly, this driving doesn't seem to hurt my fuel
economy at all even though it's mostly in 2nd or 3rd gear.

There is a similar car to mine out there with the same engine but tuned
for a bit less HP (165hp vs. 175hp) and people (often kids) driving
these cars complain of fuel economy as low as 23mpg.

--- Bror Jace

Best MPG : 5-speed vs. auto?
 

And for what it's worth, at 1800 rpm the 4.0 litre hp/torque are
roughly 70 hp and 215 lb-ft respectively which is plenty on the highway
.... even when pulling the 3500 lb boat/trailer :-)