1991 chevy suburban, What kind of fuel milage do you get?

What kind of fuel milage are you getting with your 5.7L? What if anything can you do to get better milage? I just got suburban and it's got 117,300 miles on it and was wondering if this is good for a suburban that
is 15 years old? Please if you know of a way to make btter fuel milage drop me a line and let me know.
Thank you Shane
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
thehawk93 wrote:

My 1990 V1500 gets around 11 to 12 MPG. I just bought it a few weeks ago, so have not had time to get a tune-up or do much to try to improve it.
-Michael
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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. ----------------- TheSnoMan.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Our 87 1500, 4X4 gets around 14 on the road. It's all stock, no mods.
Al
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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. ----------------- TheSnoMan.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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....
Thank You Shane
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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 ago.
Mike D.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.