How long can you get out of a set of spark plugs.

rsewill · Mar 7, 2012

3930dave said:
What I'm on about is really restricted fuel filters - at this point, I'd say you can't count on the fuel rail being at spec pressure.

Consider WOT, and low fuel pressure. Injectors max out at what - maybe 90% duty-cycle (I'm just grabbing a number out of the air, but it is obviously less than 100%). So, you can end up delivering less fuel than what should be delivered at Wide Open Throttle.

Some people don't let their fuel filters get anywhere this bad. Some people never drive at WOT.

What I'm talking about is hitting the end limit, in terms of fuel delivery.

Many people on TBN are into doing proper regular maintenance.

One thing I've learned hanging around my buddy's shop is that many of the general public have come to interpret Low Maintence as No Maintenance. I've seen FI fuel filters that when they are drained, they look like you are draining an OIL filter !

Most modern FI measures air mass, but AFAIK, not fuel mass - making it hard to run rich, but possible to run lean.

D.

Must be all that ethanol dissolving all the crud.

3930dave · Mar 7, 2012

Ford (gas) trucks went "filterless" somewhere around '09.

Filter sock in the tank got upgraded, as did the screens on the injectors. Seems to work, at least up to the point where you have enough sludge built up to cause driveability issues.

At that point, you are dropping gas tanks and/or pulling injectors. But hey, you've avoided the "hassle" of changing a filter ! :confused2:

Nothing I own is new enough to worry about, but if I owned one w/o an external fuel filter, I'd be using something like TKO 2000 once a year.

D.

(With apologies for thread drift.....)

super55 · Mar 8, 2012

No worries about the thread drift. :thumbsup: It brings up a valid point. I know a lot of guys were saying changing at recommend intervals which is sound advice I can't argue with what a manufacturer recommends but how far do you go with it.

Most makers recommend rebuilding/replacing injectors on diesels within 100k I am kinda curious if diesel owners are as religious about maintenance intervals on there injectors.

westbrooklawn · Mar 8, 2012

I have a 2004 5.4 F150 with 147,000 miles on it... runs great and gas mileage is as good as it has ever been. Just because of procrastination on my part I missed the 100,000 mile changeout. I've talked to several mechanics and every one of them says "if it is running good, don't mess with the plugs"... some have told me a plug change at the dealer will run over $400, and that's if things go fairly well.

Diamondpilot · Mar 8, 2012

3930dave said:
Modern quality spark plugs are pretty good, and do last a long time.

Personally, I don't like taking plugs past the vehicle manufacturer's recommended change interval, and would side with changing 'em earlier than that.

One other factor to consider in this debate - fuel filters.

From what I see coming through my buddy's shop, many people stretch out (or just don't change it at all) the change interval on fuel filters. These cars can end up running somewhat lean, IMO this ends up beating up the sparkplug pretty hard. Esp. in this scenario, stretching the plug change out even further is playing with odds I'd rather not.

If you change your plugs yourself, even if the improvement in fuel mileage is just a few %, you don't have to drive very far to have the plugs pay for themselves.

D.

Many of the newer vehicles do not even have fuel filters. I have owned two vehicles that did not have them and have had no issues.

I think in general the fuel supply is much better and the stations do a good job filtering the fuel at delivery. I have not had a fuel filter issue since 1986 when I was in college and had a filter plug on a Toyota truck. I was buying all my fuel at a mom and pop and I remember the fueling prior to having a issue the pump was only pumping 1/2 speed. I should have know something was wrong and stopped at that point but did not.

Chris

Diamondpilot · Mar 8, 2012

westbrooklawn said:
I have a 2004 5.4 F150 with 147,000 miles on it... runs great and gas mileage is as good as it has ever been. Just because of procrastination on my part I missed the 100,000 mile changeout. I've talked to several mechanics and every one of them says "if it is running good, don't mess with the plugs"... some have told me a plug change at the dealer will run over $400, and that's if things go fairly well.

The $400 price tag is in part the price of the plugs. A good modern plug is nearly $20 at the dealer each. Yes, you can find them on sale for about $10 at Auto Zone and such but they just cost now days. Figure $200 for parts or more and the rest labor at $75 per hours. Just the cost of doing business now days.

Chris

Barnone · Mar 8, 2012

"I mean they say a oil filter is only good for about 3k miles but most people I know don't change there oil to about 5k now and don't seem to have any issues."
You told you that ridiculous statement? My Ram has a 8k oil/filter change schedule. My Toyota had a 7.5k oil/change schedule.

rsewill · Mar 8, 2012

Barnone said:
"I mean they say a oil filter is only good for about 3k miles but most people I know don't change there oil to about 5k now and don't seem to have any issues."
You told you that ridiculous statement? My Ram has a 8k oil/filter change schedule. My Toyota had a 7.5k oil/change schedule.

My VW Diesels are 10k oil changes and some on a VW forum believe 15k is easier on the cam.

buickanddeere · Mar 8, 2012

super55 said:
Not sure if this is in the right section but figured since they run off of fuel it would be close enough.

How long can you get out of a set of spark plugs? I know this is going to be an extremely variable answer based on type of engine, carb vs. FI, etc. I was more specifically looking at cars. I have a 2000 silverado and an 06 durango but with between 100-110K miles on them. Both run great and have no reduction in power/fuel economy.

I know for a fact that neither have had the plugs replaced and they are running platinum or iridium plugs. My question is: If the vehicles are running fine is there any real reason to replace them? Changing plugs these days can be a real P.I.T.A on newer cars. I was wondering how long some have gone on a set of plugs before they noticed any reduction in performance.

An extra wide gap from worn electrodes forces those $$$ coils to boost voltage to compensate.

JDgreen227 · Mar 8, 2012

Diamondpilot said:
The $400 price tag is in part the price of the plugs. A good modern plug is nearly $20 at the dealer each. Yes, you can find them on sale for about $10 at Auto Zone and such but they just cost now days. Figure $200 for parts or more and the rest labor at $75 per hours. Just the cost of doing business now days.

Chris

Been a LONG time since I have seen dealership or garage labor at $75 an hour. Last time our Lesabre was at Mr. Monkeywrench's for an oil change back in early 2008, the rate was $82 an hour. It's probably well over $100 per hour now, and I think I saw a post elsewhere on TBN where a member said he was quoted $141 per hour.