My 1999 Deville 275 HP has 103000 miles on it . Is it time to change the plugs and wires? Over the last 6 monthes I have noticed my gas milage is down a bit , even though the car starts and runs as good as always . And if it is time what kind should I install ?
Thanks in advance for any info on this issue .
RRG

It is time. Most here recommend AC Delco OEM replacement.

Thank you . So if I go to a parts place and ask for AC delco they will know which ones to give me ?
RRG

If I'm not mistaken, the white emmision sticker underhood should list the proper number for spark plugs.

For the best price and fast shipping I'd recommend http://www.rockauto.com. Be prepared, the wires are NOT cheap.

Thank you . So if I go to a parts place and ask for AC delco they will know which ones to give me ?
RRG

I think the platinums are AC Delco 41-950 - that's what came out of my 99 STS. Tell them you want what is in the car now. If they can't figure it out, go somewhere else.

Thanks guys . And Ranger you are right , the plugs are only $40 plus shipping but the wires are $103 plus shipping . Anyway thats not bad for 8 years of driving . I was going to trade it in on another "year old one" , but I found out mine is not worth anything to the dealers . So since it works and looks like new I will drive it another 8 years . Even with the chance of costly repairs , financially it's a no brainer .
RRG

Just incase you are thinking that $103 is high for the wires, check with a dealer parts dept. I never though plug wires could be that expensive. It's no wonder the dealers are getting $500 for a "tune up".