NONE of the above...
Do a good tune up with new AC Delco Rapid-fire or Platinum plugs
(whichever you have) replace the plug wires/cap/rotor as required, do an
oil/filter change and use a good oil (Synthetic/crude your choice), Lube
all fittings and check/change the rear gear lube, transfer case lube,
and trans fluid. Change the air filter (use a quality filter like Wix
or Baldwin) Check all belts and hoses for wear/damage. Check the clutch
on the fan to make sure it is operating properly. Check the tires for
wear and damage and air pressure. Make sure the brakes are in good shape
and the parking brake is releasing fully.
Then just use good driving skills to lessen the amount of
starting/stopping. The 5.7 has never been a high MPG engine, usual range
runs from 9 - 18 MPG depending on the vehicle and it's wind resistance
and the driver. The Yukon is NOT a good vehicle for mileage since that
is not what it was built for anyway. Sorry but that's the facts.
As for the gimmicks and crap that claim to increase mileage they should
be sold right next to tickets for the Cardiff Giant....
All of what Steve said is good concrete advise. One thing that I might add
is have a 4 wheel alignment done to the truck. Talk to the alignment
technician and ask him about the least amount of toe in that he thinks you
can get by with and still drive safely. Two things this will do for you, one
the tires will last longer and two less rolling resistance.
Interesting observations--thanks, I am just curious about
improving mileage--I've overheard others debating the subject. I knew
when I bought this truck that the mileage would be lousy, but the way I
look at it is the truck is just an added insurance policy when involved in
a accident and used for a couple times a year of hunting and off roading..
Thanks again for the advice--I will not be buying any of those things
I would recommend a Jacobs high energy ignition system with Mileage Master.
I have it installed on an 88 K1500 ext. cab, long bed with the 5.7L. I can
get 20mpg on the highway. I also have a good free flow exhaust system and a
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