gc302047

iTrader: (4)

bad gas mileage, like 10-11 used to get 13-14, yeah i have a huge 3600 stall and 2.73s... this is all city do you guys think if i changed the plugs it would be better? i just put some new msd wires on. the plugs have been on the car since the first of jan 2009

01ssreda4

iTrader: (96)

I change my NGKs once a year regardless of miles, which is typically very low at maybe 2-3k a year at best. Actually, in all truth, I run copper core plugs in all my cars, and change them all once a year. Obviously DDs have significantly more miles then the SS. I never have spark plug issues doing it this way.

RPM WS6

iTrader: (3)

Time doesn't matter. Plugs have a shelf life of forever, if not used.

Mileage (or, more specifically, engine run time and operational conditions) is what causes wear. The more short trip/stop-and-go driving/idling you do, the shorter their lifespan will be.

In ideal conditions, you should be able to get a soild 30k miles out of the stock heat range NGKs (TR55). The colder TR6 will probably start to deteriorate by about 10-15k miles.

Now, if you have a less than ideal tune, massive cam with lots of overlap, oil burning issues, etc., plugs will foul up more quickly.

Your recent mileage drop could be due to several things, plugs being just one. Dirty filters, dirty MAF, aging O2s, etc., can all cause the drop as well. Or any combo of the above.

Jon@Texas-Speed

iTrader: (18)

I would doubt that is what is causing your issue but for under $20 change them and see what it does. Not a bad idea to throw a set of wires on while you're at it. Let us know if you need either and we'll get you fixed up!

Jon

Nightrydass

Sorry for the question, but; do O2s really "wear out"? if so; when/how often should you change them?

My gas mileage is a little lower then it used to be also. my car is an M6 with boltons, minus headers, on a stock tune. I have the SLP MAF (i kno, i kno...) and my plugs probably have close to 30K miles on them (BOSCH 2x platium. Again, I kno, I kno. I bought teh SLP and Bosch plugs when i knew diddily dick and believed that the HP advertised was the HP you actually got ).

i checked the plugs last year and they looked new, so i didnt change them. the O2's are as old as the car (93K miles). My gas mileage is about 15mpg around town (though i will admit i . )

sidewayz28

iTrader: (24)

bump for the above question..
Im replacing my stock O2s with Denso's for piece of mind

PGUFF

iTrader: (12)

To the guy above with old plugs and o2s, I would probably go ahead and replace both with that many miles. Use NGK plugs, and only worry about the 2 front o2's, rear o2's only measure cat function

RPM WS6

iTrader: (3)

Yes, they can stop functioning, but if that happens you'll get a code. As they age though, the readings are not as precise as brand new O2s, so A/F might be slightly less than ideal. It's not going to have a serious effect on MPG unless they are bad enough to throw a code, but it could have a minor effect that might become more noticeable when compounded by other issues.

15mpg in all city driving with aggressive driving habits really isn't "bad" mileage. You might pick up 1-2mpg with some new O2s, new plugs, and new filters (air and fuel). Don't expect big gains though. Now, if you got 15mpg on the highway while driving like grandma, then yeah I'd say something is wrong.

This is often the result of a valve cover gasket leak. The oil seeps down and works its way into the plug threads, I've seen this on my cars before. As long as you don't have any oil fouling on the actual electrode or ground strap, then I wouldn't worry about it.

Nightrydass

Thanks RPM, that is kind of what i figured.

No, the oil on the plug is just on the threads and it is very minimal. I thought the oil on the threads was common, and was caused by knows "LS1 oiling issues"? There IS a tiny bit of oil in my cacth can, and i installed that way AFTER i did the plugs. The electrode, ground strap, and porcelien (sp) are all clean. There is also NO oil around my heads, or valve covers. O well, not going to worry about it. nature of the LS1 i guess lol. I have been thinking about ditching the SLP MAF, and going back to the stock one though....

Yes, it is funny; i bought another vehicle to DD about 2 yrs ago to keep the wear and tear OFF of my SS. Yet, i drive the car HARDER now that my SS is just my toy. I don't beat the **** out of it, but i shift higher then i used to, get on it more then i used to, and whind out the gears more then i used to. Funny how that works. lmao

Next summer Ill do my plugs and change the O2's out.

RPM WS6

iTrader: (3)

No, this is not an LS1 specific thing, it could potentially happen with any engine. It only takes a tiny drop of oil to coat those threads, and even the most minor of valvecover seeping can do this. Oil seepage can collect right at the point where the back of the plug meets the head, then as you unscrew the plug it will coat the threads. The leak may be intermittent (gasket shrink in cold weather, etc.) and you might not even see it now. You'd have to be burning a serious amount of oil in the combustion chamber to be able to push liquid oil out into the plug threads; enough that you'd see smoke out the exhaust and the entire plug tip would be caked with oil fouling. Even then I'm still not sure if liquid oil would "leak" out, unless you had a dead cylinder that was blowing it by but not burning it.

That's what counts. Those are the areas that tell you what's really going on inside the combustion chamber.

And you wonder why you don't get record high gas mileage? J/K!! Sounds like your MPG is pretty much where it should be for your driving style. If you really want to test it, try taking a long expressway trip (~100 miles or so) and stay in high gear/low rpm situations as much as possibile. Fill up before and after and see what you get for MPG.

sidewayz28

iTrader: (24)

x1,000,000

gc302047

iTrader: (4)

my tuner tuned my car in open loop so my front o2's dont function att all i think. he told me it does not effect mpg at all is this true? just wondering

sidewayz28

iTrader: (24)

im still new to tuning but, from what ive read your front O2s are constantly trying to bring you to stoich under part throttle conditions.. so i dont think running in open loop is going to give you the same/better gas mileage. plz someone correct me if im wrong