Plug Wires And Gas Mileage?

[jdaniel83]

A buddy of mine recently changed the plugs and wires in his 2002 Chevy 5.3L, and he decided to replace the 7mm wires with some performance 8mm wires. He says it feels like it has a bit more power but his gas mileage has dropped by 1-2 MPG. I am going to replace my plugs/wires soon and was thinking about doing the 8mm swap also but if they cause worse mileage then I'm going to stick to the 7mm. Is going to a larger wire supposed to affect your mileage or is this just a weird happening?

[jro909]

stay stock

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If adding HP was as easy as upgrading to a thicker plug wire, then I would have done it by now. In a stock setup, there is absolutely no advantage to a thicker wire, except if it's in a place that may rub against metal and arc. But in our trucks, they're not.

[rebelman06]

When I had my truck dyno tuned, the guy said he thought I needed to change the plugs and wires based on some of the feedback he got. I asked him what I should run and he told me to run the stock replacement wires and plugs.

[maxwell1]

i had my truck tuned up at 90K, it was still running great.

 

I used all ac delco parts and it still runs great.

 

that is what you want, tune it before it starts to run bad and motor should run great after the tuneup.

 

leave those aftermarket parts at the store.

[dewfpo]

The mpg drop your buddy is seeing is more likely from the spark plugs (and gap he used) than from the plug wires.

 

DEWFPO

[jdaniel83]

Thanks, that's what I was thinking. Glad I got some more informed opinions then the ones I was hearing from. Thanks again for the responses.

[Matthias]

Don´t get me wrong guys but how can you believe this with the thicker wires and more horsepower...it´s like waiting for santa? Do you do that too?

[Black02Silverado]

Adding super duper plug wires on a stock engine is like killing mosquitoes with a sledge hammer. Over kill and not needed.

 

Why he had a mpg drop sounds more like a plug gap issue or bad set of plugs over the wires. Maybe even a bad batch of fuel from his last fill up?

[jdaniel83]

Yeah I think it was incorrectly gapped plugs cause I talked to him today and he had regapped the plugs and his mileage went up.

 

And no WhiteDenali I do not wait for Santa, I go to sleep so that he'll come by and give me my presents.