Ok, my car was getting awesome gas mileage, 21-22 mpg, in town driving, and after I changed the plugs, she's getting under 20 for sure. They're OEM platinum plugs, and I double checked the gap before installing. They were installed about a month ago. Can new plugs kill gas mileage? I've read awhile ago, some member didn't ever change his plugs because he was getting some awesome gas mileage as well, and why kill a good thing. After the new plugs, I noticed her starting up way better and she drives a tad different. But it wasn't till at the pumps, I noticed her being a hog. Any suggestions?

 

SD? When did the weather start getting cold in isoland? Colder weather = worse mileage.

 

colder weather+ new plugs= has nothing to do with poor gas mileage, what grade gas are you using? 89 91 or 93? fill your tires up with air when it got cold? that could be one reason why.

 

Always fill up at the same gas station, and always use 91. Yes, tires got filled up w/ air when it got cold, I check my tires regularly, probably weekly, ****? Yes of course, she's my baby. Air filter is new.

 

make sure your tires are not over inflated. also, it sounds like you are talking about ` to 2 mph? that could be a difference in how you drive, the type of 91 gas you use, etc... you may want to throw some fuel injector cleaner in there....

 

Is there a brand of fuel injector cleaner you recommend? Any brands to stay away from?

 

use BG fuel cleaner, you can get it at some Nissan dealers and Direct Tire sells one that is a step above the one Nissan sells.

$16-$25 a can.

 

In some states they switch to a winter blend of gas which causes poor milege. If your stations just switched that could explain it.

 

Colder weather = longer open loop operation/lower tire pressures (if unchecked); thus lower mileage. Add short trips and you have a huge decrease in mileage. The plug change is just coincidence.

 

To my surprise, I found the car getting better milage on 87 than 93