I added a vacuum gage to my daily driver (89 Taurus SHO) to monitor my fuel
economy. If I drive the car at 13" of vacuum at all times or higher, I get
26 miles to the gallon. If I have fun with the car and do things that take
the vacuum to 0, the car gets 25 miles to the gallon. Bottom line, the gage
is neat to watch, but I wouldn't get too tied up on what it displays going
down the highway. Granted, the engine may have more vacuum out of
overdrive, but you're also spinning around the engine 20% faster to get this
higher vacuum reading. You have to fill the cylinders with fuel every other
revolution independent of the vacuum reading. The slower your engine is
going, the better your mileage should be. Use it as a gage for acceleration
ONLY, and you'll probably be better off.
Am I way off base here?
-----Original Message-----
From: owner-oletrucks@autox.team.net
[mailto:owner-oletrucks@autox.team.net]On Behalf Of Don Slaney
Sent: Saturday, March 17, 2001 8:28 PM
To: old-chevy-truck@yahoogroups.com; OLETRUCKS;
6066_GMC_Truck@egroups.com
Subject: [oletrucks] OVERDRIVE/MILEAGE/ECONOMY?
Off Topic! But?
I'm at a loss to a problem I have, not serious, but even General Motors
Canada does not have an answer. But I bet someone on here has one?
I have a vehicle to haul ole trucks home, [ONLY GENERAL MOTORS PRODUCTS]
a 1986 American Chevrolet Caprice wagon.
It has a Fuel economy {vacuum guage} in dash.
When driving on a straight flat highway, in overdrive, it reads just above
1/3 toward the best fuel economy.
When I pull shift lever to ordinary drive, the economy increases by 50% the
needle closes in on maximum economy. Which suggests I am getting better
mileage in ordinary drive than overdrive.
This happens when tow-baring an ole girl home to the collection or plain
highway driving. It has almost 400,000 KMS or 248,560 miles. Motor never
touched, except plugs and a fuel pump. Uses no oil and power to burn.
Any all suggestions, ideas greatly appreciated.
Regards to all, Don. ppm@dlcwest.com
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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