increase in mpg (bit of a surprise)

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Old 11 Apr 2006, 11:17 am   #1 (permalink)
onehappymadman@yahoo.com
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Default increase in mpg (bit of a surprise)

Just filled up my '96 this morning, and was surprised to see it made
30.0 mpg this fill-up. Before, it had been in the 28-29 range. The
strange thing was, I think I drove it more in the city *this* time than
I did when measuring 28-29 mpg...

I'm curious which of the following could have contributed to the
increase in mpg:

1. Statistical out-lier. Just a fluke - won't show up in the future.

2. I removed the coarse portion of the EGR filter (but put the fluffy
part of the filter back). Would this affect mpg?

3. I started Auto-RX treatment 1,000 miles ago. Would this affect
mpg...?

onehappymadman

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Old 11 Apr 2006, 11:22 am   #2 (permalink)
onehappymadman@yahoo.com
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Default Re: increase in mpg (bit of a surprise)

Forgot to mention - it's got just over 135k miles on it, and it's a
4-cylinder.

I *did* change to synthetic ATF in the diff, but that was a few months
back, and before my last 3 readings of 28, 29 and 30 mpg...

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Old 11 Apr 2006, 03:15 pm   #3 (permalink)
Justa Lurker
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Default Re: increase in mpg (bit of a surprise)

onehappymadman@yahoo.com wrote:
> Just filled up my '96 this morning, and was surprised to see it made
> 30.0 mpg this fill-up. Before, it had been in the 28-29 range. The
> strange thing was, I think I drove it more in the city *this* time than
> I did when measuring 28-29 mpg...
>
> I'm curious which of the following could have contributed to the
> increase in mpg:
>
> 1. Statistical out-lier. Just a fluke - won't show up in the future.
>
> 2. I removed the coarse portion of the EGR filter (but put the fluffy
> part of the filter back). Would this affect mpg?
>
> 3. I started Auto-RX treatment 1,000 miles ago. Would this affect
> mpg...?
>
> onehappymadman
>


Is this about the time of year when gasoline blend changes from "winter"
to "summer" ? IIRC that can account for a change in MPG on the order of
magnitude that you observed.

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Old 11 Apr 2006, 04:13 pm   #4 (permalink)
m Ransley
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Default Re: increase in mpg (bit of a surprise)

Warmer weather.

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Old 11 Apr 2006, 04:46 pm   #5 (permalink)
Daniel
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Default Re: increase in mpg (bit of a surprise)

If the auto-rx has been in there for 1,000 miles it is time to drain it
out and change the oil and filter.
If you're trying to track 1-2 mpg changes from one tankful to the next,
you're seeking an accuracy that is not generally possible.
Most likely variance is that the auto shutoff on the gas nozzle doesn't
always switch off at exactly the same point and you need to watch
mileage over a number of tankfuls to get an average reading.
When I bought my 1977 Toyota pickup truck, the gas gauge only worked
for the top quarter tank - from full to 3/4 full, so I always very,
very carefully watched the number of miles on the odometer and filled
up again at least 50 miles early.
One day the truck died on the freeway and I had to coast across fast
moving traffic to get to the offramp and to a mechanic. Took about an
hour before he finally correctly diagnosed the "no-start" problem to
"out of gas." (even though the mileage hadn't been reached)
Moral of this story is that there is variance in pump fill ups.

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Old 11 Apr 2006, 05:01 pm   #6 (permalink)
onehappymadman@yahoo.com
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Default Re: increase in mpg (bit of a surprise)

Directions said to change 1500 miles after...

Besides, isn't it supposed to be the oil *after* the autorx treatment
that has to be changed after 1000 miles?

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Old 12 Apr 2006, 11:54 am   #7 (permalink)
Daniel
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Default Re: increase in mpg (bit of a surprise)

They must have changed. Used to be change after 500 miles.

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