Anyone use this in your gas tank to help pass "difficult" emissions? Supposedly the ratio is 1 part denatured alcohol to 4 parts 87 octane. And you need to run the tank down to almost empty, add a gallon of alcohol and 4 gallons of 87 on the same day of the smog test. After the test, fill the tank with high octane to dilute the alcohol. This is supposed to be for the older high mileage engines like mine. I have til the first week of June to get my 77 smogged so I may try it.

what % of alcohol? 70% and 90% are available at the drug store, have no idea where to buy 100%.

That's about 22% ethanol. Have you run a pre-test to see what your actual emissions are? The real fix may not be that difficult and probably won't put your fuel system at risk.

You might already be running 10% or more ethanol, from the pump.

Denatured alcohol is just ethanol with impurities left in or added, so that you can't drink it. Benzene or some small amount of chemicals used during purification are typical.

what % of alcohol? 70% and 90% are available at the drug store, have no idea where to buy 100%.

Denatured alcohol is 100% ethanol, just with trace amounts of chemicals to render it non-potable. It is available at hardware stores. You could also get pure grain alcohol from the liquor store, but that's pretty expensive to run.

I have not done a pre-test but have considered it. The problem here is you are not allowed any adjusting during the pre test. So I would still not know if any adjustments I do to it will make it pass until I take it back. That could become a PITA you know?

dj, I believe it is 90% alcohol.

Yeah but I could drink the left overs SteveJ

The pure grain alcohol that is

Edited May 19, 201410 yr by rcb280z

Consider what you are doing with EtOH. You are adding extra oxygen into the combustion process. If you're high on CO, that might help. If you're high on NOx, it won't. If you're high on HC, I would think it would increase your CO.

Yeah, Im thinking I will run hotter than normal. So Im not convinced the alcohol is the answer.

I've found that setting everything to stock specs., timing mostly, and running the idle air screw out as far as you can without inducing a miss, will get me through the Oregon DEQ tests. Timing advance and retard changes the ratio of combustion byproducts that they test for. It's probably why idle has a whole set of parameters tied to it, like initial timing, idle enrichment fuel, idle air bypass, etc. Air fuel ratio and timing both change immediately as soon as you open the throttle.

When I lived in California I used "guaranteed to pass" which sometimes seemed to help. I never knew what was in the stuff (and never tried to drink it).

It gets pretty good reviews, Amazon.com: Customer Reviews: CRC 05063 Guaranteed To Pass Emissions Test Formula - 12 Fl Oz.