[V6-12v] High Mileage 100S

Elliott Potter mailinglist at eep.burdell.org
Mon Jun 28 09:42:05 EDT 2004

On Mon, 28 Jun 2004 James4ihl at aol.com wrote:

> That may be because your commute is so short.
> [...]
> the fuel economy for the first few minutes is frighteningly poor <17mpg
> for the  first few minutes/miles, then it gradually leans out as the
> engine warms up.
> [...]

I'll vote for this one as well - the ECU stays in "open loop" mode until
the O2 sensors warm up to operating temperature, which takes a couple of
minutes.  Then it runs somewhat inefficiently until the engine coolant
reaches operating temperature, which can take several more depending on
the weather and whatnot.

The other thing to point out is that when you take so many short trips,
you have lots of gunk build up in the engine that would normally get
cooked and blown out; the EGR valve is especially bad about that.

In addition to the oxygen sensors, you might try putting a bottle of
Techron in the last tank of gas before you change the oil, and give the
car an Italian tuneup.

> In a message dated 28/6/04 5:06:36 am, cdniederst at comcast.net writes:
> > Geeze...I only have 113k on my '92 100S. My commute is <15 miles per day
> > (that's total), so I don't chalk up the miles like you guys. In terms of gas
> > mileage, I never see the numbers Jon is getting. I generally get ~18 mpg
> > around the city, maybe ~23 mpg on the highway. I always run 93 octane gas,
> > change the plugs at 30k intervals (with the OEM ones), changed the O2
> > sensors at 75k, plus air and fuel filters every 15k, and never really see
> > any difference. Car runs just fine, just wish I'd see the better gas
> > mileage.
> >
> > Craig
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