lost fuel efficiency

[jfindlay]

My 1988 GL 1.8 SPFI has typically been getting about 32-36 mi/gal.
During the latter half of this year I have had to do a lot of
maintainence and repair on the car and now I'm getting around 27-28
mi/gal. The only thing I can think of that might be related is that
I've put some fuel injector cleaner in the fuel tank. Are there other
things that I might try/observer?


Justin

 

[Rebecca B.]

Did you put new tires on? My average mpg went down when I put new tires
on my car.

 

[jfindlay]

Did you put new tires on? My average mpg went down when I put new tires
on my car.

I did. Interesting notion. Maybe I can even experiment with tire
pressure too. I figured higher pressure would translate to a more
elastic, from an energy conservation perspective, contact with the
road, but perhaps this is the wrong parameter to optimize for.


Justin

 

[Edward Hayes]

Tires from different manufactures can have diameters different by
several percent. Add to that you now have about 8/32 more tread could
be your difference i.e. you are going farther per tire revolution and
it is not reflected in your Speedo reading.

 

[Rick Courtright]

I did. Interesting notion. Maybe I can even experiment with tire
pressure too. I figured higher pressure would translate to a more

Hi,

In "today's" tire world, it seems there's more variation in fuel economy
from tire to tire than 15-20 years ago. More tires are "performance"
oriented, meaning softer compounds, more aggressive tread patterns, etc.
It's not a perfect measure, but I've found an inverse relationship
between fuel economy and the UTQG mileage figure: in other words, a tire
rated as "Treadwear 200" usually turns in worse fuel economy than one
rated as "Treadwear 500" kind of thing. There CAN be big differences in
fuel economy based on those parameters, plus the larger diameter Ed
mentioned, and the pressure issue.

For myself, I've generally found a slight increase in pressure (2-4 psi
over the door sticker) would help fuel economy, and handling, w/o
hurting the ride. Above that level, you've gotta experiment to find what
works FOR YOU!

Also, you mentioned recent "work" on the engine. What all was involved?
Can you rethink anything that can definitely relate to economy issues,
like timing, new sensors, that kind of thing? Maybe even a significant
change in driving patterns? (A friend became seriously worried about the
mileage on her new Camry--she bought it just before she retired, and
drove it 35-40 miles each way, pure freeway, while working. Now, since
she's quit working, she never seems to go more than about five miles at
a time and seldom sees the freeway. BIG change in economy!) You did
mention injector cleaner: it may be your mileage drops while the
cleaner's in there (or it may not--I've had cars that dropped off,
others didn't change, one even improves when there's a can of cleaner in
the tank!) and then comes back as the cleaner's burned up. It may also
be, if it's been a long time since any kind of cleaner's been run
through, that you'll need a second can.

And then there's always the issue of "winter gas" and poor mileage that
comes up about this time of year...

Rick

 

[jfindlay]

In "today's" tire world, it seems there's more variation in fuel economy
from tire to tire than 15-20 years ago. More tires are "performance"
oriented, meaning softer compounds, more aggressive tread patterns, etc.
It's not a perfect measure, but I've found an inverse relationship
between fuel economy and the UTQG mileage figure: in other words, a tire
rated as "Treadwear 200" usually turns in worse fuel economy than one
rated as "Treadwear 500" kind of thing. There CAN be big differences in
fuel economy based on those parameters, plus the larger diameter Ed
mentioned, and the pressure issue.

I just got lucky and found a complete set of 4 new tires at the local
self-serve discount junkyard.

For myself, I've generally found a slight increase in pressure (2-4 psi
over the door sticker) would help fuel economy, and handling, w/o
hurting the ride. Above that level, you've gotta experiment to find what
works FOR YOU!

And that is the material point. In my case I'm in constant need of
watchfulness and sometimes retrenchment. "The vehicle is not a toy or
a laboratory but ultimately just transportation."

Also, you mentioned recent "work" on the engine. What all was involved?

Minor work on the AC, power steering, and engine water systems. I've
replaced the air flow meter with one from the junkyard (the old one
died), the oil pan gasket, and the entire secondary ignition system
during the past year: plugs, cords, distributor cap, rotor, ignition
coil.

And then there's always the issue of "winter gas" and poor mileage that
comes up about this time of year...

It is reasonable to believe this is also a contribution.


Justin