MPG help

JSEsterly

JSEsterly

New Member
Joined
Jun 30, 2005
Location
Jacksonville
Just got my "new" 86 burb.. it gets about 7-10 mpg (350).. wondering what kind of things will actually help that...Not looking for "Product X" says it gets.. more looking for "I added a K&N and it gave me +2 mpg and 5 HP" I dont really care if I add HP, but I dont want to loose any, more intrested in MPG. Thanks~!
 
Will help to know more. What gears? what tire size and type. What aspiration, everything there and stock? What exaust? how recent a tune up? what plugs? What ignition? Driving style? What Octane do you use?

Many things to concider.
 
Chip good point.. I just read the K&N post, and it made me think about this 350. Dont know what gears..yet, guy says he thinks they were changed out.. have to open it up and look. Its got 33s on it, dual exhaust, and dont know last tune-up/plugs ex.. plan on doing that all this weekend. Course thats why I made this post.. Trying not to buy into the "splitfire" plugs are the best/K&N thing.. Driving style.. not a lot of hot rodding..its a burb afterall.. right now using 87.
 
Do the tune up with the recommended plugs, wires, etc. No snake oil. Make sure you have no vacuum leaks. Make sure your tires are inflated properly and evenly (side to side). Take the 300 lbs of crap that always accumulates in the back of a vehicle out, and drive like there is an egg between your foot and the gas pedal.
 
If your 86 Burb is a 3/4-ton, it probably has 4.10 gears. Plus it probably has the TH400 trans, so no overdrive, right? If that's the case, then that's definitely a part of your gas mileage problem. Are you correcting for your tire size? If your speedometer is off, then your odometer is not recording the true amount of miles you're driving, so you can't calculate MPG accurately.

My dad has a 1991 Burb with good running 350, TH700R4 with overdrive, K&N stock replacement filter, dual exhausts with one cat on each side, 3.42 gears, 33-inch tires. It is lifted 2 inches. He is getting freakin 19MPG, mostly highway driving, and it is honestly did it - I did the calculation and corrected for his speedo error from the bigger tires. Even without the speedo correction, the calcs show 17 mpg.

I've got a 1990 K5 Blazer with tired 350, TH700R4 with overdrive, aftermarket cat and muffler on single exhaust, 33's, and 3.73 gears. No lift. I get at least 14 mpg, but can't touch the 19 my dad gets.
 
IIRC '86 or '87 was the last year for a carb.
It isn't going to get the mileage of an FI motor.
I have an 88 3/4 P/U 350 FI gets around 17-19 MPG.



When I can keep the 700 R4 in it long enough to check MPG that is!!! :mad:



Never had a truck with a carb'd 350 that got that good.


In addition to what has already been said -


All the fancy stuff (Split fire, purple wires, fru fru cap & rotor) does little.
A good tune-up with the factory spec parts - use quality brand name stuff, not brand X - will do you as well as anything.


A few T/U things to check.


When you have the rotor off - make sure the advance weights are free and rotate the rotor mtg part of the shaft when you pull them out from centre.
And that they return on their own when released.


Pay attention to ign timing.



If you have a vac pump (MightyVac) make sure the vac advance is working.


Make sure the EGR is working correctly so you can keep the timing up where it belongs.


Check the hot air riser valve in the air cleaner assy to make sure it opens once warmed up.


Check cold air intake hose - make sure it is clear and in a place where the air flow is not blocked.


You do know it has a fuel filter in the carb - right ?
Cheap filter may not have the check valve in it.


Carb bowl vent line. make sure it is clear.
Check to make sure the carbon canister purge valve is not putting any vacuum to that vent. It can & will suck gas out of the vent.



Not tune-up, but something to check.

Check the fan clutch.
If it is frozen or if it has been replaced with a solid fan, it can actually rob some HP & MPG. If it is loose, it is dangerous.
You want a working fan clutch or quality flex fan on there.


HTH
 
A simple approach that will help you alot:

Easy on the skinny pedal.

Let your vehicle pick up speed going down hill and let it slow down going up hill, this can make a tremendous difference.

Let off the gas just as you are cresting a hill.

Remember, whatever position your gas pedal is in, that is the amount of gas you are using. Your speed at that point determines your gas mileage. So if down-shifting nets you more speed with your foot in the same spot, then you will get better mileage. Lugging an engine gives you horrible mileage.
 
87 was the first year for TBI. Best thing Chevy did since they built the first 350. My dad's 87 1/2 ton with 3.73s, 700r4, and 31's got 17mpg most of it's life. City, highway, didn't matter. 17 mpg. Towing brought it down to about 14-15. Now, at 210k miles, it's mine. It's tired, I think the cam is completely round! It still gets 12-14mpg, and I'm not easy on it.


In other words, switch to TBI for a fairly cheap mpg boost.
 
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