So I only have 40,000 miles done, the manual says to change the plugs every 60,000. The reason I am looking to do this is my MPG has been dropping slowly over the last 10,000 miles. I was averaging 24.3 mpg, I am now down to 21.9. I have replaced the air filter and the tire pressure is ok. The next most logical move I would have thought was to look at the plugs. The car does not seem to be mis firing and drives really smoothly. I really only use the car to get to work and most of it is open road without traffic. Is there anything else you would suggest to look at other than hooking the car up to measure air/fuel mixture? It is not a fuel grade issue as it is a slow drop off in MPG over month and multiple fill ups are involved.
Getting back to the plug question are there any gaskets I need to replace or just pull the hoses out? When I install the plugs and re-attach the hoses do I need to bleed the coolant? If so whats the best way to bleed the system? thank you for your help