i have been using the bosh 4 plugs for about two years on all cars that i have had they work really good on most of them and i had to return some that were defective usally i had no problem at the parts store until today my wifes festiva started missing and using alot of gas so i went and bought another set and car ran fine took the old ones back to get refund because there is a lifetime warranty on them they told me to send them back to bosch in germany.when i allways exchanged them or got a refund at the store ..... you know this really too much of a hassle for plugs that cost 6$ a piece and only last about 1-2 years.....