Changing oil = more likely to pass emissions?

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Does changing motor oil just before emissions inspection have any bearing (no pun intended) on the ability to pass?

Or is it a myth?
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-John
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For what it's worth-I wouldn't think so unless the oil that is in there has thinned out excessively and is able to get past the rings.

I could be wrong though...
 
Yup. Less contaminants in the oil will help with your PCV system and any oil that gets burned in the combustion chamber. It's not just a myth.
 
If simply changing motor oil will get you a pass on emission testing (assuming that it was a boarderline fail beforehand) then boy! you got a serious mechanical issue there (oil burning, excessive blowby,valve guides worn, oil control rings stuck, etc.)
 
Change oil, replace PCV valve and sparkplugs.
This was standard procedure for my high mileage cars. It did make a difference. The good news is, we don't need emission testing any more.
 
Actually, it will. This was told to me by a State Certified Inspector while I was getting one of my vehicles inspected. "Regular oil changes will most certainly help your vehicle pass the emissions tests". Note he said regular changes... Maybe an oil change just before an inspection may help some on a vehicle that has not had the regular oil changes, but, I would think it would be marginal. Then again, I think it would also depend on the oil one uses, the milage, and condition of the vehicle.
 
If it were good I'd expect only for hydrocarbons. NoX are a function of overheating/carbon buildup/wrong timing and CO poor ignition.

As others have said, a properly functioning PCV should evaporate fuel about as fast as it gets in the oil though.
 
I agree with doubleclutch, regular changes are best. One problem I think might show up if you just changed your oil is the burning off of the lighter components of the oil. Just a thought
 
I agree that regular interval changes done throughout a motor's service life are helpful - for all facets of a motor's life, not just passing a smog inspection. But the original post asked whether an oil change just before submitting the vehicle for a mandatory state inspection would increase the odds that the vehicle would pass. If that motor isn't gonna pass on what's already in the sump, fresh oil and a new oil filter aren't gonna help enough, either. If there's a liklihood that the motor is polluting too much to pass, put the money into a new PCV valve and a new air filter. Motors live or die on smog inspections on how well they breathe which in turn determines how efficiently they're able to burn fuel.
 
Changine the oil before the test was very important with the old carburetor equipped cars.The oil would get contaminated with gas due to over choking when cold and the fumes would be pulled into the intake via the PC valve.Was most important in the winter/spring.With a fuel injected car the gas getting into the oil is very uncommon and the O2 sensor,etc. would pretty much compensate if there is any.

In Wisconsin the 1996 and up OBD 2 cars are just scanned for codes...exhaust is not analyzed.
 
Just went thru emissions test on my 86 Toy (22R/Carb) and passed with flying colors. Did an oil change, PCV, and fuel filter before the test. Drove her a while before getting to the testing center and kept it running so everything was good and hot. The testing process quit half way thru and I got a quick pass.

Not sure if the minor tune-up helped, but I don't mind replacing a few $5 dollar parts every 2 years.

J
 
quote:

Originally posted by q2bruiser:
Just went thru emissions test on my 86 Toy (22R/Carb) and passed with flying colors. Did an oil change, PCV, and fuel filter before the test. Drove her a while before getting to the testing center and kept it running so everything was good and hot. The testing process quit half way thru and I got a quick pass.

Not sure if the minor tune-up helped, but I don't mind replacing a few $5 dollar parts every 2 years.

J


While you do not mention the miles, nor OCI's, I also had a 1987 Toyota Landcruiser (since sold) with app 250,000 miles that also passed with flying colors!!! I no longer have the paper work on the emissions tests. Again the question is why do much short OCI's without verifications? Or in my two cases, verifications show the emissions over 10 and 14 years to be absolutely stellar with almost no extra care other than inspections etc during scheduled maintainance intervals?? So in effect the required smog checks were a total waste of money. Now of course from the regulatory agencies a source of FREE MONEY. So basically I did app 17 OCI's (@15,000 mile OCIs) when 84 OCI's would have sufficed
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(@3,000 mile OCI's) This vehicle was used 5 days a week as a business delivery and client vehicle.

[ March 04, 2006, 04:00 PM: Message edited by: ruking77 ]
 
My 87 Toyota PU failed smog. I changed the oil, added a bunch of Lube Control in the oil and a double dose of Fuel Power in the gas tank and it passed with flying colors. It blew very close to zeros across the board. I'm looking for the receipt somewhere out in the garage.
 
In a car which fails on HC emissions and burns oil, an oil change may help because of viscosity shearing. Similarly, using the highest permissible oil viscosity, such as a 20W-50 on a tired old engine, may reduce HC emissions enough to pass the test.

If Auto-RX really conditions ringpacks as claimed, running a course of Auto-RX may also improve one's chances of passing.

By the way, none of my cars has ever failed a smog test. My formula is simply to make sure the plugs, PCV system, and air filter are clean and that all of the "plumbing" is in place.
 
I do not know, but the "proof is in the pudding."

I went through a 10 year CA state so called random, but once chosen "MANDATORY "SMOG ONLY" on a 1994 Toyota Landcruiser with 116,000 miles, with 12,000 miles on a normal (for me) 15,000 mile OCI with (the much vilified) FRAM oil filters.

SMOG ONLY test stations are specifically tasked to actually get (flunk) cars off the road, vs a normal smog check which is normally done as almost a loss leader service.

In my opinion, this (at the time) 10 year old Toyota Landcruiser BADLY needed a tune up. The vehicle passed with absolutely flying colors!! After being relieved of app 100 dollars, for the SMOG ONLY TEST, (these cost more than normal smog inspections) I took out the first bi annual smog certification results done app 8 years earlier and the current results (8 years after) were better than when NEW/or certainly when the first bi annual smog certification was done. So as a result I delayed the 120,000 mile major tune up till 125,000 miles.

Over the 12 years, I got oem Toyota and Fram filters because of the discount for a case of 10 oem filters. In the case of Fram's, 2 filters for 5 dollar sales. But WalMart sells single (Champion Labs made) SuperTech Brand for $2.07. So when the current stash runs out I will switch.
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I could have done a UOA but at the 120k mark (actually 125) the Toyota mechanics take off the valve cover to check the innards and to measure for the need for a valve clearance adjustment. This job fetches hundreds of dollars so I think one can see the motivation here. However they said not only was the adjustment essential at new car specifications, but they could see the original tool markings on the usual wear points and the innards were SPOTLESS!!

I look forward to another 125,000 trouble free miles. Again germane to the topic, 15,000 mile OCI's.

[ March 04, 2006, 01:04 PM: Message edited by: ruking77 ]
 
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