I have a 89 V1500 burb that I bought new and now has 180K. I just put
600 miles on it last week (a 250 miles trip and a 350 miles trip) and
got 18.2 when I checked it. I know that engine really well. If you are
serious about better MPG you can do a few things. First keep tires
stock and with smooth tread and near max pressure with load range "C"
tires. Next, reset timing to about to 8 degrees BTDC rather than stock
TDC (easy to do on this TBI engine) and FORGET about using 87 octane
fuel! I use 93 most of the time but in cooler weather I will use 90 or
so when I can find it. If you are addicted to the though of 87 octane
there is not much you can do. THat generation engine responds well to
advanced timing and better fuel where as the newer VorTec engine are
much more difficult to have timing reset as it is all electronic while
TBI are mechanical and electric hybrid. My vehical runs great. I have
gotten as high as 19 MPG on long trips (it has a 40 gallon tank) and
in urban driving it will do around 15 or so and it will turn in 17 MPG
even pushing 70 to 75 with AC on. When it was new and using stock
timing and 87 octane, I was doing good to get 14 on highway with A/C
and it wa a slug at times. BTW even if MPG was not better with 93
(though it is) I would still use it in it because with timing reset
and 93 octane it is a different engine and runs smoothly and pulls
strong from the lightest throttle input. Nice and crisp.
Try the timing trick with better gas it works. Those TBI engine used a
combination of mechanical /centrifical advance and 20 degrees of
electronic advance used for knock control This design could not
retard spark to more than base line timing plus centrifical advance
where the Vortec can run timing anywhere in the 40 BTDC to 40 ATDC at
any time ECM commands it to. Because of the TBI's timing design you
can force timing to a more advance curve and together with better fuel
gain MPG and power/responce. As it sits the timing curve it pretty
retarded from factory to tolerate 87 octane. (modern VorTecs retard
spark and performance without you even knowing it) One word of caution
though if you do this timing mod, DO NOT run 87 in it anymore because
knock control will not be able to retard spark below the advanded
baseline timing and it will knock big time.
Hey, snoman sorry but I'm new to this truck and know nothing about it.
What do you mean by btdc? is this retard or advance? how could I do this
without a timing gun? also I live in utah and preminem is only 93 oct. out
here plus and reg. are 87 and 85 oct. I mean if it's going to do better in
fuel then I will pay but I will need more help with how to do the
BTDC: Before Top Dead Center. With increased octane you can have a more
advanced (15 vs 11 degrees btdc) ignition timing. On a much older truck
which did not have computer controlled ignition timing I set this having the
brake on HARD, tranny in drive or reverse, and increased the RPM a bit and
advanced until it started knocking and then backed it off a few degrees. I
cant get much more specific as this was only about 6 vehicles and 20 years
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