Wow, it sounds like I have some work left to do! I am lucky to get an
indicated 24-25mpg at 55mph. My average has been about 15mpg for city
driving, but I do have a bit of a heavy foot. Are there any main causes of
poor fuel economy specific to the EFI cars? I thought the plugs might be the
issue, but although it runs much better, fuel economy doesn't appear to have
jumped dramatically. All the old plugs I removed were a nice tan colour, so
I am not concerned about internal engine condition or oil fouling. Maybe a
vacuum leak? Leaking fuel in HSA? How about an O2 sensor? It runs so very
nice that I don't see it being something major. Oh, and I suppose I should
change the air filter...
William
----- Original Message -----
From: "Dick Benjamin" <dickb@xxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Friday, May 02, 2003 10:06 AM
Subject: Re: IML: 83 EFi spark plugs, MPG update...
> Yes, the original tire size was 205/75/R15, as the door sticker states.
If
> you use the original tire, you will get better acceleration, and better
> "indicated" fuel mileage, but lower actual fuel mileage. If you use the
> larger tires, you will get longer tire life, better actual fuel mileage,
and
> slightly poorer acceleration. I have run both sizes on the 4 '81-82's I
> have owned, and have decided that next time I "retire", I will go back to
> the original size, although I certainly won't do it until I wear out the
> 215/75/R15 Michelins that are on it now - which will probably take as long
> as I am able to drive.
>
> According to the dash readout, I am getting about 28 MPG at a steady
> (indicated) 55 MPH on a flat,level road with no headwind or tail wind. If
I
> were running the original tire size, this would read about 10% higher due
to
> the odometer correction, plus some additional correction because I would
be
> going through air resistance about 10% slower, so I'd estimate the readout
> would be 32 MPG or so.
>
> According to careful measurements on our most common trip, which just
> happens to be almost exactly 500 miles (Temecula California to Lake Tahoe
> California) I get about 25 MPG average on the trip. I drive between 75
and
> 80 on the trip about 2/3 of the way, the rest is mountain driving on windy
> roads, so I probably average about 60.
>
> This number is the result of dividing the known actual mileage by the
total
> gas consumed, determined by a brim full fill-up before and after each
trip.
> Note that this 1000 mile round trip involves about 30% driving in very
high
> altitudes (8000-9000 feet) and some very long hills (11 mile, 6% grades
in
> two places). We make this trip once or twice per year, and have every
year
> since I have owned the current '81 (since 1987), and the results are quite
> consistent.
>
> For around town use, I average about 18 MPG (ours is not a very congested
> town, by eastern standards!)
>
> For those who question the wisdom of taking these cars on trips, I can
> report that we have driven these cars all this time without ever having to
> call the man with the hook to get us home (although a failing fuel pump
made
> me worry a bit on a trip to Boise one time in 1989, but we did make it
under
> our own power!).
>
> Dick Benjamin
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