My GDI plus 4 has been a bit flat lately so decided it was time for a major service plugs filters and oils. It's done 8000miles but given its 9 years old thought it wouldn't hurt. Wow what a difference goes like a scalded cat now. Rear two plugs siezed but came out eventually noticed the plug gaps were set at 25thou which is about half of what they should have been. Mpg is now over 40 from 35 which is welcomed.