Chevy & GMC Vans

On a recent trip I got 16.97 miles per gal with my 1994 LT without towing anything.Is that normal for my model van?.Should it be more?.What could I do to improve it?.Plugs/wires/ injectors are a little over a yr old.The van has 165,000 miles on it.Did a oil change before the trip using a Wex oil filter.Has a new air filter.Has a new ERG screen gasket.I am going to sell this van(hopefully)this spring proving Old Yellar's V8 conversion is done.I find the LT somewhat of a gutless on the hills where in cruise control it slows down requiring me to step on the gas to maintain the set speed.

I seem to recall my '94 doing better. Maybe fresh oxygen sensors? Clean the MAF sensor?

Sounds kinda normal, Gary. The Smilievan gets 12 around town and 17-18 on the highway. 168,000 on the ODO. I do carry all of my balloon equipment in the van. That's probably 800-900 lbs. I wish it got better but I'm happy with it. It runs flawlessly and serves it's purpose perfectly.

Gary, I got close to 20-21 on the highway in my 95 before larger tires. After tires and 4.10 gears, mileage still stayed around 18. I know from reading on AS that people get anywhere from 15/16 to 21-23 on highway, not sure why.

My '99 'Stro AWD went from 20MPG hwy to 16MPG after the lift and the bigger tires.

Sure would love to get it to 20 mpg without breaking the bank.Wonder where is the biggest bang for my buck for that?.

GEJ wrote:Sure would love to get it to 20 mpg without breaking the bank.Wonder where is the biggest bang for my buck for that?.

Rear end gears are the best bang for the buck. My old 95 2WD that skippy has now can easily get 20 mpg on the highway with 4.10's where it had a hard time getting 16-18 before. When I drove it back and forth to work, hammering on it and banging through the gears, it would get 15 mpg day in day out.

I get about 16 17 MPG in The Van, and I know I need new O sensors. And I need to do the exhaust. The Van is stock by the way. What about the air filter, would it help to move to a cold air intake, or just increasing the airflow through the airbox?

LiftedAWDAstro wrote:

GEJ wrote:Sure would love to get it to 20 mpg without breaking the bank.Wonder where is the biggest bang for my buck for that?.

Rear end gears are the best bang for the buck. My old 95 2WD that skippy has now can easily get 20 mpg on the highway with 4.10's where it had a hard time getting 16-18 before. When I drove it back and forth to work, hammering on it and banging through the gears, it would get 15 mpg day in day out.

Dean,
Remember this one has a posi rear end in it.We looked at the codes at the house.What you think the costs would be for a conversion to 4.10's or 3.73's?.


Thanks all for your replies.

It would be between $500 and $750 to do the gear swap depending on the shop doing it and what they charge for labor. Gears are around $150. Master install kit is around $100 and the rest is labor/misc.

Well my um.. 2004 Astro, stock, carrying nothing but it's own weight manages about 14-16mpg.
freaking crap: my '86 Astro, even before the resto-mod, got 18-20.
2004......1986... and it's this much worse? o.0

mazade wrote:Well my um.. 2004 Astro, stock, carrying nothing but it's own weight manages about 14-16mpg.
freaking crap: my '86 Astro, even before the resto-mod, got 18-20.
2004......1986... and it's this much worse? o.0

The difference is that your 1986 was about 1,000 lbs lighter!

Yes,the 1994 LT is over 4,000lbs and I don't know the wt for the Ole Yellar 1985 Astro high top because Tn where I got it doesn't include wt's in there titles.NYS assigned a wt for it where I had it tiled in my name.

From what I read the MPG's vary greatly for even the same yr and mileage vans.Now that is kind of weird.Don't think the driver could effect it that much because I do think most of us are just D.D. normal drivers.

Gary, my 305 equipped 89 Astro has 3.23 gears in the differential and it consistently gets 15 mpg. It has done this whether it was EFI or carbureted. Unfortunately, it also requires better than 87 octane (it runs best with 93) or the engine will rattle itself to death.
There isn't much I can do about its octane requirements, but I'm wondering if installing 3.43 gears wouldn't help with the fuel use. As it is now, the engine turns 1700 rpm at 60 mph and it feels to me like I'm giving it a lot of throttle pedal. Is it possible that I'd be using less gas pedal if I had steeper gears in the differential? I do know that the engine is practically lugging now at 60 mph.
Since I need to use higher octane fuel, I've begun to 'custom' mix E85 with 89 octane gasoline. The E85 has an octane of 105, so the 305 would thrive on it if the carb was jetted bigger and its internals, the fuel regulator and the pump, could withstand the solvent action of the ethanol. Presently, I run the tank low and then fill up with approximately 20 gallons of gasoline and 4 gallons of E85. I'm not sure just what resulting octane is in the tank, but I find that I can up the ignition timing beyond what just 89 octane can run.
I've got a well-worn 1984 Chevy 350 sitting in storage that might just get reborn as a strictly ethanol fueled engine and then find itself powering my Astro. I need to do a lot of research on alcohol fueled engines before I rebuild the 350 into one, though.

Safari Rob sounds liek a good project and one that I would be very interested in. make sure to post it if you do it.