[jkinney]

2008 Solara V-6 3.3. 130K miles. I installed new plugs. Car seems to run fine, idle same as before, BUT mileage has dropped (car guage on dash) from 27.5 (about 60,000 miles) to 24.9 since plugs changed. No significant change in driving. Any thoughts?

 

[Pvt-Public]

Did you use the plugs listed in the manual or under the hood? I hope you didn't use what ever the parts store had, or fell for the super duper quad electrode,or those "High-Performance" type crap. It seems Toyota engines are happiest with the recommended plugs.

Is there any rough running? I know the back plugs can be a PITA. All connections good? Maybe knocked of some connector or other?

 

[jkinney]

Nope, used a match to the originals. No rough running.

 

[Kingdom934]

Is it the gauge that shows the avg mpg? If so, those things are very inaccurate...at lease in my 2004. Best way to track miles the old fashion way of getting the miles traveled and the amount of gas filled up.

I use an app called Fulley to monitor my levels and see if any recent changes may contribute to the mpgs.

 

[JohnGD]

I'd use NGK plugs. And make sure they're properly gapped. Make sure the connections are tight.

What brand of plugs did you use? What part numbers and gap?

 

[jkinney]

Denso, I think the number 11, although I don't remember letters. They were same as factory plugs. Other than gas mileage the performance seems to be the same.

 

[hardtopte72]

It is probably nothing. The only way to be sure is to hand calculate. If you use OEM Denso SK20R11 plugs, you are fine. I use those in most vehicles I service.

 

[jkinney]

OK, so I just thought of something I might have done wrong: When I got the upper intake manifold loose, one of those little chrome pins (there are 6. Don't have any idea what they're called) in the manifold kept falling out. In fact once it fell down the manifold, but I managed to get it out with a magnet. Antway, by then I was getting pretty frustrated, so I put some gasket sealer on it, and stuck it back in, and it stayed. However, now I'm wondering what those pins are, and if they're supposed to be able to move. That's the only thing I remember that I possibly did wrong. Thoughts?

 

[hardtopte72]

OK, so I just thought of something I might have done wrong: When I got the upper intake manifold loose, one of those little chrome pins (there are 6. Don't have any idea what they're called) in the manifold kept falling out. In fact once it fell down the manifold, but I managed to get it out with a magnet. Antway, by then I was getting pretty frustrated, so I put some gasket sealer on it, and stuck it back in, and it stayed. However, now I'm wondering what those pins are, and if they're supposed to be able to move. That's the only thing I remember that I possibly did wrong. Thoughts?

I wouldn't have put any gasket sealant near the intake manifold. If it idles fine, it's unlikely you have a leak.