re. factory instrumentation accuracy & mpg

Brett Dikeman brett at
Sun Jan 26 13:10:56 EST 2003

At 12:24 PM -0500 1/26/03, ben swann wrote:
>Yes - peeve # 2 on the new aquisition of the '91 200 20v tq avant.  Has
>SJM chip with 2.5 bar pressure transducer AFAIK.  Gas mileage abysmal
>on the way home - 20MPG and no I was not easy on the gas and probably
>averageing over 70.  My '87 5000 tq would get an easy 28 mpg under the
>same conditions.  I thought Motronic was supposed to be superior at
>engine management, including economy, over CIS (CIS/motronic).
>What's up with that?

-wider(and different) tires
-several hundred pounds heavier
-flares probably don't help with airflow
-higher valvetrain resistance(probably negligible, but...)
-oil different viscosity, perhaps, that what you run?
-oh yes, and with the chip, did I mention "a lot more HP"?
Accelerating onto the highway full throttle can influence average
economy considerably if you have a chip.

Cruising on the empty highway, leaving it set on cruise control, on
the hakka Q's, I'll get about 24 tops at 75-80 indicated.  My old
5000 would do about 2mpg more, usually, same speeds.

Off cruise control, traffic for passing?  More like 22 or worse.

Keep in mind tires can play a factor here, and not just tire
pressure.  The MXV4 "Energy" for example gets a few(very few) more
MPG than the regular MXV4.  Let's also not forget elevations, wind...

"They that give up essential liberty to obtain temporary
safety deserve neither liberty nor safety." - Ben Franklin

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