I was wondering if I get an oil change prior to getting a smog check - will it give better results for the smog check- please advise - thanks. (btw - i have a 94 mercury van villager with 150,000 miles on it.)

If a car barely misses its smog test, the list of possible remedies includes an oil change. It may not help very much bit it certainly can’t hurt.

No. Smog Test measures fuel/air mixture, NOX, CO2, engine performance/timing, etc…

It most certainly can give you better results… Have you ever heard of blow-by??? Open up your oil filler cap when the engine is running. Feel the air coming from the crank case??? That is exhaust, or blow-by. If your exhaust can enter the crank case with the engine oil, then the engine oil can …

I once failed a smog check with a perfectly good car, by not warming it up sufficientlty. Make sure you have a new or very clean air filter, all plugs are firing properly and your crankcase ventilation sytem is working properly. These items are far more important than changing the oil. If the engine…

A smog test also checks for hydrocarbons. If the oil in the crankcase has a lot of miles on it, it becomes more volotile. These oil vapors are then introduced into the combustion process via the PCV system. If there’s a lot of oil vapors in the crankcase gasses, this will effect the HC count. Test…

Yes, changing your oil will lower the readings for the reasons already posted. In most states, less than 3% of the cars tested “fail” the test. It’s just another revenue source, like a toll booth. With that low a failure rate, smog testing makes no difference in overall air quality. If the 3% that …

OIL CHANGE before SMOG CHECK?

Maintenance/Repairs

keith3267 June 4, 2007, 1:09am 3

Actually, new oil will smoke less that older oil, so it might help in a marginal engine.

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OIL CHANGE before SMOG CHECK?

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