New water pump = better MPG?

[jp1]

Just wanted to toss this out there...but since I replaced the water pump on the KJ, the gas mileage has gone up about 2MPG. I haven't seen any better than 16 and change for quite some time. Since the water pump, I'm getting 18 in town and 19+ with some highway mixed in there. I haven't seen 19MPG in I don't know how long.

Could the only WP been putting such a drag on the engine? I've changed nothing else other than he WP.

Weird...but I'll take it.

 

[jnaut]

Possible, but not likely. My guess is there's some other factor.

 

[belvedere]

winter vs summer gas formulation?

 

[tjkj2002]

winter vs summer gas formulation?

Bingo we have a winnereclipsee_gold_cup.g:

Actually a new waterpump will decrease your MPG's by a fraction of a tenth of 1 mpg due to actually pumping the coolant correctly.

 

[LibertyTC]

That and the outside air temp is warmer, less warm up time, and gets system open quicker.

 

[jp1]

I'm not buying the winter/summer gas thing. It's the middle of June already.

It just seems like a weird coincedence that the MPG improved right after the water pump. Oh well.

 

[JeepINgeek]

isnt there a bearing in the water pump? if that bearing was shot the increased drag could decrease mileage.. then the new free pump would result in increased mileage.

 

[jnaut]

isnt there a bearing in the water pump? if that bearing was shot the increased drag could decrease mileage.. then the new free pump would result in increased mileage.

Yes, it could and gas mileage loss vs. gas mileage gain from old/new waterpumps is probably largely a wash.

My waterpump was about as bad as it could get... so bad, it assploded all over my engine. I saw no statistically significant change in gas mileage either way.

To test gas mileage theories in non-laboratory conditions, you have to track it for a long period of time for trend observations, plus add in 100's of other variables.

For instance, some variable that apply to me:

During summer, my commute changes due to my daughter's school/summer schedule.
Warmer weather in general will give you slightly better mileage especially on shorter trips.
Summer winter gas formulation.
Oil changes.
New/old tires and wear over time.
Tire inflation changes between summer/winter.
Spark plug wear.
More highway trips made during summer than winter.
Vehicle continuing to age.
Sticky brake caliper replaced.
Voluntary changes in my commute: I'm no longer feeling Ambaum blvd, so I'm going to take Marginal Way via 509, unless I'm not taking my daughter to school, then I'll stick to Ambaum, unless I choose the 509 to Roxbury via South Park because I like it when the wind blows my tasteful blonde highlights. leghump.gif

Pinning changes (for the worse or for the better) in gas mileage on any one thing is very difficult to do, which is why the best way to do it is in laboratory conditions:

Put vehicle on closed circuit. Measure for temperature, wind speed direction etc.

Run vehicle on closed circuit at precise speed for given amount of time.
Repeat several times, and calculate mileage as average.

Make change to vehicle/engine/tires whatever.

Measure for temperature, wind speed direction etc.
Run vehicle on closed circuit again at same precise speed for given time.

Compare mileage. Loof for statistically significant changes and report with any changes in ambient temperature, wind speed, direction etc.

 

[indieaz]

Even with the A/C running both the KJ and my vette do about 1-2mpg better in summer on average. It's very easy to compare becuase i drive the exact same routes every day of the week, mostly highway mileage and only a few lights.

This is due to the vehicle warming up much faster (warming up in a matter of minutes) and tending to run a little bit warmer. The warmer your engine, the more efficient it is.