I replaced my original plugs with a set of auto lite platniums about a month ago. I thought new plugs would help a little in the MPG department. Now it seems like my MPG have dropped a mile or two. I don't know if this is from the colder temp or the plugs.

Has anyone experienced similar results?

Im thinking of throwing a set of copper in just to see if there is a difference

 

I forgot to say i also did an oil change and put in Mobile 1 5w30. It calls for 10w30 or 5w30 in cold weather.

 

Generally speaking, the Magnum V8's don't like the high-temp platinum plugs. The intake manifold design plus PCM timing curves tend to run on the hot side with OEM plugs, going even hotter with a fancy plug is just going to make things worse by inducing detonation. Through word of mouth, a lot of people have switched to the Autolite 3923 copper plug over the years - it's a little shorter than stock and one heat range colder, tends to work well with our engines.

 

When I had my truck on the road for the two weeks it was on the road I put in the autolites and I noticed a difference, they aren't that expensive either.

 

Thanks for the info. I think i might put some copper plugs in.
My truck seems to run ok with the plats but i've lost a mpg or so. Who knows it might be the colder weather.

 

I put in Bosch Platinum and they run great. That was 67,000 miles ago. Did you keep the metal sleeves around the plugs? They were a painand I was wondering if they were necessary?

 

I wasn't thinking and took the first two out. after that i just left the others in and worked around them.

By the way how is your gas mileage?

I average about 11 thats 70% city and 30% highway. Im very easy on the pedal. I was hoping at geting at least 13-14.

guy I know with chevy's are geting 14-16 with about the same portion of city/highway.

 

If you do go coppers, go with the autolite 3923's like R/T said, not the factory recommended though.

 

Might be the winter mix of Gasoline, that'll drop MPG.You north of the Mason-Dixon?

 

I can attest to the 3923's- I replaced perfectly good stock plugs with these and the truck idles and accelerates smoother, especially at highway speeds. At $1.29 a plug, not a bad deal either.

For the heat shields (the little tubes) I found it easiest to stick the plug in the magnetic socket and with an extension on, just turn it lightly as if you've got the plug in your hand. Didn't have a problem cross-theading one of them. Took all of 15 minutes too, first time changing plugs on this truck.