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Does wider gaped spark plugs increase mpg?
This is B.S.! Hell No! 12 (57.1%)
Of course! Makes perfect sense. 0 (0%)
Get your kitty out of my intake. 6 (28.6%)
Gap'em if you got'em. 3 (14.3%)
Total Votes: 21
4% better MPG with larger spark plug gap
Topic Started: Nov 1 2013, 04:14 PM (2,486 Views)
ascensions
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Je conduis une petite voiture.

Posted Image
Via, there's a part of the book that states adding .006 gap to your factory plug gap (can) add 4% better fuel mileage to your vehicle.

Can't say if it's true or not, just thought it was interesting, and worth the share.
Edited by ascensions, Nov 1 2013, 04:15 PM.
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rjsdotorg
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In the 80s when I drove a FB 400 I saw a table with rough guide to changing your gap to compensate for uneven compression and smooth out idle etc.
Never seen since.
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Geo Glenn
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What's in your engine?

:bsmeter
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idmetro
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If this were true then you should continue to get ever improving mileage as the plugs wear...

Up to some point when the gap would be too wide and the engine wouldn't run.
Edited by idmetro, Nov 1 2013, 06:52 PM.
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iamgeo
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Is that a fact....or just a rumor?

I'm going to try it. I just install new plugs and wires a couple weeks ago. I already have a baseline to compare to.
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2000Firefly1.3L
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gay !
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Turbo Dan-O
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Obsessive Car Detailer

iamgeo
Nov 1 2013, 08:10 PM
I'm going to try it. I just install new plugs and wires a couple weeks ago. I already have a baseline to compare to.
Cool. Not like it's going to cost anything. I don't think it will change anything but it's worth a try. ;)

I have an extra MSD 6AL box I have thought about trying out on the Metro just to see what happens. :hmm

I don't know the specs but it has been my experience that our factory ignition is VERY good. I have tried a few different plugs, gaps, and even "indexed" them and could not tell any difference. My old school carbed V8s are another story though. ^o)
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iamgeo
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Is that a fact....or just a rumor?

I gapped my plugs .010 bigger so they are at .050. We will see what happens.
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ascensions
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Je conduis une petite voiture.

So I gapped mine to .47, and the hood says .39, and it definitely changed the way it drove. I won't know till the end of the week if it effects MPG... but it should be interesting.

If you're in for some interesting read, I found this last night:

http://www.cruzetalk.com/forum/27-fuel-economy/6468-spark-plug-gap-fe-1-4t.html

Of course it's not our car, and they have a very small gap from the factory... but it does seem to suggest there is something to this in at least a few applications.
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iamgeo
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Is that a fact....or just a rumor?

I put over 125 miles today. I noticed a bit more pep. Seemed to have a bit more power going up hills.
Gas mileage also seems a bit better.
Today was a lot cooler than last week. Cooler days mean lower mpg.
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iamgeo
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Is that a fact....or just a rumor?

First tank down. About 380 miles.
More power? Yes.
More MPG? No!
This tank was 42.6 mpg. Four mpg less than last tank.
Will do one more tank and see how it fares.
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JADEDSL2
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Resident WraithSlayer

iamgeo
Nov 4 2013, 11:11 PM
Cooler days mean Posted Image
Fixed that for ya. :nfs
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ascensions
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Je conduis une petite voiture.

Just for the heck of it, you might want to back down to a .44-.47 gap. Several citations on the internet suggest no benefits were gained by going larger than .45

I have a 96/3/5 and gaped mine about the same time I posted this too, and my mileage did go up, but nothing incredible (under 1 MPG). It did seem like it took the ECU about 200 miles to figure it all out for myself, so I too will give it another tank before calling it busted.
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iamgeo
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Is that a fact....or just a rumor?

Will be going to a .046 after this tank.
I wanted to go to the extreme first then back down.
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rmcelwee
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I think the a larger gap means a hotter spark. I know I used to keep mine a little tighter (and two steps cooler to keep from detonating) when I was doing the whole turbo thing (theory was that the boost blew out the spark but I never really believed that). SO, I would guess that a larger gap would give better MPG. Perhaps run a little hotter plug as well. I don't play with my car that much because 48-56 MPG is good enough for me. Some day I will get around to experimenting.

Ascensions, I think you might be on to something...
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