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

[bcp]

In the late 1950's when i started driving and caring for a car, I remember a Farm Journal article on plug life in tractors. They repeatedly tested tractors as the plugs aged. IIRC, the average reduction in power, at 100 hours of plug life, was about 20%.

That might not mean anything with modern plugs, oils, fuels, tractors, or cars.

Bruce

 

[Soundguy]

on points based systems running on 6v and low energy ignition.. i bet it was a huge deal.

same reason I pull and clean mine yearly in my gasser oldies.....

 

[JDgreen227]

In the late 1950's when i started driving and caring for a car, I remember a Farm Journal article on plug life in tractors. They repeatedly tested tractors as the plugs aged. IIRC, the average reduction in power, at 100 hours of plug life, was about 20%.

That might not mean anything with modern plugs, oils, fuels, tractors, or cars.

Bruce

That's interesting to learn, my dad was farming with both an 8N and a Jubilee back then and I remember his griping about having to change the plugs. May be a stupid question, but suppose you tried sparking a 1960 vintage plug with one of todays ignition systems? Would the old plug be able to deliver the same service life it did using a points and condensor system? Or would it fail quickly?

 

[Soundguy]

plugs pretty much a plug.

voltage potential at the spark gap is a function of how wide the gap is and the atmospheric pressure.

if you have an hei that produces 40kv, but only 8kv is needed to jump the gap.. it jumps at 8kv. it don't wait till 40..

 

[3930dave]

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.

 

[Soundguy]

lean? hmm... maybee if it had no computer, sensors and a carb with manual needles on it.. like.. um.. a 60 yer old tractor?

wouldn't the computer in a modern car use things like the o2 sensor and MAF/MAP sensor to adjust the EFI or TBI? and if there is enough flow to keep the plenum and rails up to miimum book spec.. um.. i'm not seeing a lean issue????

soundguy

 

[timswi]

lean? hmm... maybee if it had no computer, sensors and a carb with manual needles on it.. like.. um.. a 60 yer old tractor?

wouldn't the computer in a modern car use things like the o2 sensor and MAF/MAP sensor to adjust the EFI or TBI? and if there is enough flow to keep the plenum and rails up to miimum book spec.. um.. i'm not seeing a lean issue????

soundguy

Not a lean issue, but certainly a potential fried fuel pump on the new stuff...Most gassers don't even have fuel filters anymore..Much to my chagrin.

 

[Soundguy]

really? no fuel filters? that seems like asking for clogged fuel injectors???

 

[3930dave]

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.

 

[timswi]

really? no fuel filters? that seems like asking for clogged fuel injectors???

Nope...Guess they count on the 'sock" in the tank...Probably not everything is like this, but more and more of the new stuff I maintain is...Fortunately, none of the ones I've mantained have ever had a fuel related issue, so I guess it works.