View Full Version : Another dumb question

06-20-2010, 12:49 AM
How often are you supposed to change spark plugs?

Ive had the same ones in my truck for ~1 year, they have 35k miles on em.

And the design of my truck is dumb, i have 2 plugs per cylinder and the ones on the intake side are a Bitch and a half to change

06-20-2010, 04:19 AM
Cmon meow. Someone has to have an answer.

06-20-2010, 04:51 AM
There may be estimated or recommended service intervals, but basically if it has been a long time you can always pull'm out and take a look at the tips. If they look poopy, replace them. I know I know, not super technical advice...

06-20-2010, 05:06 AM
Depends on the plugs. I think autolites are 40K while the +4's are 100K. I would think 60 is a safe bet unless your truck doesn't feel right.

06-20-2010, 06:01 AM
well i dunno much about your truck dude..

but i change my plugs every 2-3 change oils.. :D

06-20-2010, 06:22 AM
It depends really. I don't really stick to the normal suggestions, but plug wear. If they look ugly or worn, I replace them.

06-20-2010, 06:24 AM
I check my plugs every oil change.

I run the cheap copper ones.

Often, I won't change them for a year or so, but I still check them.

The ignition system on your truck is funky. Ford put two plugs on them for emissions reasons, the Lima design was 20 years old by that point, and was never designed for modern emissions. The second plug is on the exhaust, and burns the post-ignition mixture to ensure complete combustion for emissions reasons. Not power.

06-20-2010, 08:10 AM
I go by wear too. I just replaced mine today because they were white. I know I'm not running lean, because it actually smells like its running rich, hence the reason for changing the plugs, and it doesn't seem like its getting overly warm. I might just have had the wrong heat range plugs in there. I dunno. Guess I'll see down the road.

06-20-2010, 02:12 PM
So murg, could I get away with only changing the intake side plugs if the exhaust side are still in decent shape?

06-20-2010, 03:09 PM
I'm the same as most here - I change them based on wear.

Inspect them by checking for "erosion" on the bottom electrode - a noticeable amount of metal gone indicates you need to change them.

I'm the same as Murg in that I do inspect them often as this is the simplest tool to give an overall indication of your engines current state of tune and general well being.

06-21-2010, 05:05 AM
Manufacturer recommendations can vary widely. I have no idea what they'd be on that dual system, but these are the very general rules I usually advise people with:

Copper Plugs - Around 15-25k miles.
Single Platinum(platinum tipped center electrode only) - 40-50k miles.
Double Platinum(platinum tipped center electrode and ground) - 75k miles.
Platinum/Iridium(iridium center electrode and platinum ground) - 75k+ miles.

I'm always a little conservative on my estimates, many cars after 2000 equipped with double platinum or iridium plugs have recommended intervals of well over 100k miles.

Those figures are based mostly on plug info alone though, assuming an engine in very good condition. As everyone here has alluded too, pulling the plugs and inspecting them is always the best way to go. For instance, the coupe's rings are fried. I foul copper plugs about every six months, which for me is around 5k miles. Using platinum in an engine of that condition will actually lower their life, I've fouled them in 2500 miles. There's a huge number of factors like those that can increase or decrease plug life, which is why service intervals should always be taken with a grain of salt.

06-21-2010, 06:20 PM
I try to change plugs at least once a year, unless I start to have running issues. On the alltracs, I'll change them when I have the intercoolers off. They don't come off often.....

06-21-2010, 06:43 PM
Cmon meow. Someone has to have an answer.

Nice wax job rookie !!

06-21-2010, 06:56 PM
i want a litre of cola.

Sir we dont have litre-a cola.

06-21-2010, 08:58 PM
CAPTAN - The next person who says schenanigans is going to get pistol whipped!! ...
ONE OF THE OFFICERS - Hey Farva! Whats that restaurant you like so much, you know, with the hats and the mexican stuff?
FARVA - You mean Schenanigans??
ALL OF THE OFFICERS - Ooooooh !! (4 officers whip out their guns and hand them to the Captan)