: White "burned" spark plugs?



Slick Black Cadillac
06-07-04, 03:13 AM
I also changed my spark plugs (2000 DHS) and they all were burned white almost frosty looking. The car has 95k miles on it and the plugs were original. Should I be concerned? Thank You for your help.

RBraczyk
06-07-04, 10:10 AM
Yea they should've been changed a damn long time ago.

Ranger
06-07-04, 11:10 PM
Yea they should've been changed a damn long time ago. The plugs are good for 100K. My last car (4.9) had 125K and original plugs.... and ran fine. If it ain't broke, don't fix it.

Anthony Cipriano
06-08-04, 12:15 AM
The OEM dual platinum plugs will usually run fine for well over 100K. Replacing them sooner (or at all) is purely a waste of time and money. Unless there is a specific driveability problem that can be traced to a plug then there is just no reason to remove them.

The plugs will run almost pure white on unleaded fuel. That is perfectly normal. Sometimes there will be a yellowish deposit on the plugs from additive in the fuel...but generally they look absolutely bone white.

That is one of the nice things about unleaded fuel. Between the dual platinum tips on the OEM plugs and unleaded fuel the plugs will run virtually forever.

adaddo
06-25-04, 11:30 AM
mine hit 200,000 before the change....white as well

mcowden
06-25-04, 01:29 PM
Curious - did you check the gap when you removed them? I'm interested to know how much (or if) that changed over the course of 95k miles. Other than that, some white-ish deposits are normal.

Slick Black Cadillac
06-25-04, 01:38 PM
Gap was almost up to OEM specs. Just a little bump with the plug gapper would have reset it to perfect.

Anthony Cipriano
06-25-04, 01:55 PM
As long as the platinum pads are there on both the center and the ground electrodes the gap will not change...that is why the platinum pads are there to prevent any wear and gap change.

If your plugs were prefectly white and all the gaps were fine then the plugs were probably good for another 100k.

In normal driving about the only thing that happens to the dual plutinum plugs with mileage accumulation is that occasionally a platinum pad will become dislodged and the gap will start to grow. Otherwise, unless there is another failure that causes a fouling problem or something the plugs will last virtually forever.

In the "old days" frequent plug changes were common due to the lead in fuel. Lead deposits would foul most plugs within 20K-25K so plug changes were required frequently. With unleaded fuel, nothing really happens to the plugs except the gap wearing and with the platinum, even that is eliminated.

furluvcats
06-25-04, 02:07 PM
1994 cadillac Deville Concourse just got a tune up yesterday. 182,000 miles. Changed the plugs and they were also pure white with the yellowing color where they meet the wires. I did have what looked like alot of gas coated on the #6 plug. Changed the plugs because I was getting a rough ride. What would a gas coating on a plug mean?

CAJUN-Z
06-27-04, 11:08 PM
The OEM dual platinum plugs will usually run fine for well over 100K...
That is one of the nice things about unleaded fuel. Between the dual platinum tips on the OEM plugs and unleaded fuel the plugs will run virtually forever.
Don't forget about the engine oil and O2 sensor (and the PCM that controls spark timing as well as almost everything else)...without advances in technology in lubrication and feedback via the O2, the plugs would foul almost as quickly as in the old (leaded-gas) days...

Anthony Cipriano
06-27-04, 11:16 PM
Don't forget about the engine oil and O2 sensor (and the PCM that controls spark timing as well as almost everything else)...without advances in technology in lubrication and feedback via the O2, the plugs would foul almost as quickly as in the old (leaded-gas) days...


The O2 sensor contributes very little to plug life. The data from the O2 sensor enables the PCM to control the air/fuel mixture very closely at 14.7:1 for proper operation of the catalytic converter but this does little or nothing for plug life. Actually, before O2 sensors and closed loop operation, most engines cruised and ran part throttle at leaner air/fuel mixtures. 14.7:1 is actually richer than what would be optimum for best fuel economy or but is what is required for cat operation. Leaner would be better for plug life (less soot) but the plugs last fine anyway.

What would be the magic in the lubes that would make plugs last longer? Same ZDP and dispersants and detergents. Better VI package and such but nothing that would make plugs last longer.

Plugs last longer for two reasons... Platinum pads on the center and ground electrode to eliminate wear and unleaded fuels that eliminate plug fouling deposits. Lead is conductive so when it was deposited on plugs it would rapidly cause the porcelean to "short circuit" due to a layer of lead deposits. The other additives in gasoline can color the plugs but are generally not considered conductive.

It is true that excessive oil consumption could cause deposits on a plug that would cause fouling/misfiring/shorten plug life but it takes considerable oil consumption to do this. Even at a quart per 1000 miles the plugs will look fine and last virtually forever.

JimD
06-27-04, 11:38 PM
....
It is true that excessive oil consumption could cause deposits on a plug that would cause fouling/misfiring/shorten plug life but it takes considerable oil consumption to do this. Even at a quart per 1000 miles the plugs will look fine and last virtually forever.

My engine is one of the quart of oil per 1,000 mile samples and the original plugs are still firing the mixture reliably at 129,000 miles. Probably not a record book candidate when compared to 'forever', but if it ain't broke....

I pulled one plug about a month ago (I just had to do it because I cut my teeth on leaded fuel and breaker point distributors). The plug color was good and the gap was in the area of 0.060".

Anyone want to hear about my 10 year old Briggs and Straton OHV magneto igniton lawnmower engine with the original spark plug? It runs at full throttle for hours and hours.

Got to love unleaded gas...

Anthony Cipriano
06-27-04, 11:42 PM
Yes, oil consumption has to be very very high (like with a cracked ring or something so that only one cylinder is eating oil at 1 quart per 200 miles or something) to foul the spark plugs.

The plugs are designed to operate at a temperature high enough to burn off any carbon or soot that accumulates on the tip anyway.

Look at a two stroke. They burn oil at the rate of 32:1 mixtures and the plugs still last fine. I have put over 8000 miles on a set of plugs a two stroke and the plugs were still fine and not fouled. Lube oil does not really contribute to shorter spark plug life.