Poor gas mileage on 97 SL1

The last few tanks of gas have indicated that my gas mileage has dropped considerably since I changed plugs. I could not get to the Saturn dealer to get the oem plugs, so I bought some at an auto store that are supposed to be the right plugs. But, I have only used the Saturn plugs since buying the car new and wondered if the after market plugs could cause such a dramatic drop in mileage. This is the only thing I know of that has changed since the drop in mileage. TIA, MR

Reply to
MR
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I doubt it, but it's possible since you might have the completely wrong plugs in there and not just a different brand . Another possibility is were they gapped properly? As I recall there was some incorrect information on plug gap for around that year. If I recall correctly, the gap should be .040 inches and not .060 as published in some documentation. This is from memory and it isn't what it used to be so I'm sure others will correct me if I am not right here, or you can ask the Saturn dealer if you are not sure.

Bob

Reply to
Bob Shuman

The gap on the old plugs was probably at .060 from wear and most of the new instructions call for the .040 gap. That is one of the reasons I installed new plugs was the rough idle which happens with the large gap. But, it was not suffering the poor gas mileage that I am experiencing now. I did clean the throttle valve also now that I think of it due to high idle when first starting. I could have screwed something up there I suppose, but that cleaning is pretty easy to do. Thanks, MR

Reply to
MR

What brand and type of plug did you get and what is the condition of your wires? It isnt likely a plug problem I dont think. I guess we should first ask what you consider to be "considerably". 1mpg? 5mpg?

Reply to
blahblah

Not sure about the plugs, but think they are Champions. Wires are fine. Changed those out ~75k miles ago.

I usually get ~35-40 mpg depending on city/hwy, but has dropped to about 25 mpg. Thanks, MR

Reply to
MR

Two non-plug factors:

  1. Air conditioner use. You might take it to a local A/C shop and have them check things out (or you can screw on some gauges and check out the high and low side pressures yourself.)

  1. Summer gas. Depending on where you live, in June/July they switch to a different gas formulation that has lower vapor pressure and also lower mileage.

Tim.

Reply to
shoppa

Tire inflation is also something to check and the single largest contributor to poor mileage.

Bob

Reply to
Bob Shuman

Can you give numbers? MPG before and after?

As for plugs, I've not had much luck with anything other than NGK's for my Saturn.

hth,

tom @

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Reply to
The Real Tom

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