Short trips=rich running and over time the oil absorbs blow-by hydrocarbons. Crankcase ventilation system sucks them into the intake air which can lead to excessive HC during testing at idle (high vacuum). I always had to have fresh oil and crank up the idle to the max they allowed (1100 rpm IIRC) to pass, but that testing ended in Seattle for vehicles over 25 years old.

Stuart

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of David Beierl
Sent: Saturday, September 23, 2017 1:30 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Emissions Test Failure

When I was first putting my '89 on the road, I went from hydrocarbons "too
high to test" to a clean pass by changing the oil.

Yrs,
d

On Fri, Sep 22, 2017 at 7:24 PM, Mike <mwmiller6@att.net> wrote:

> I've also been told an oil change helps. Don't know how though.
>