1995 GMC Safari HWY Beast! But poor fuel mileage..

[95SafariRunner]

Alright, I'll be completely honest here, I'm terrible with forums formatting, but I'm going to give it a shot!

I have a 1995 GMC Safari, Hightop, RWD, OBD1, 167k miles, and many more to go!

I travel a lot, as often as I can, I'll take the van. Very comfortable, spacious, and etc. The 4.3L v6 has been more then reliable! Its amazing! Buttttttt I can only seem to squeeze 19mpg out of her! At 65mph.. I live in a state where people constantly run 80 and over, so I'd like to pull 75mph, but my fuel mileage just tanks... I've read a lot on this forum, from the shadows, I've seen people brag about 23mpg, running 70-80mph. How!?? Now I understand, that clearly my aerodynamics are a bit... different from a standard Safari, i.e. the high top. But! I actually used to get WORSE fuel mileage before I smacked the hightop on!

So I'm here asking for advice, to get the best MPG and best HWY cruising speed. As previously stated, I get 19mpg HWY,
Cruise control set at 65mph,
Tires at 35PSI,
87 octane in the tank,
And only carry about 300lbs of cargo (Myself included)

What would y'all say to change for better MPGs?

Also side note, I busted a bolt off the stock cast iron exhaust manifold, and I'm replacing them with a lighter, cheap pair of headers, and maybe a cat delete. Hoping that will improve performance on the 4.3L? Maybe? Better air flow?

[Bigforkg]

Nice Safari you have there. Far as milage I would say that's about it. Do you know the rear end ratio? Those saying 23 mpg+ I find that hard to believe. If your already going to put the headers on then free up the rest of the exhaust system as well. Have you replaced cap and rotor, plug wires, plugs, air and fuel filters?

[zzimmer3]

I'd say that's going to be your gas mileage. That's about average for these vans. But, more importantly I'd like to ask more specifics on that push bumper you have there. Please.

[SheldonYoung]

Our SurFari only goes from Boston to Daytona, and we're lucky to squeeze 21mpg at best, with an empty load.

That's not bad for a vehicle like that.

I sold my Work Astro and replaced it with a Ford F150 Van, which gets half that mileage!

(Did you install the Bull Bar? I love it!)

[02GMC]

We have a 2002 with 200K on it, had a 1998 prior. This thing went from OK to FL 21 years in a row plus Pacific NW, CO many times etc. NEVER broke 19 mpg anywhere, usually 18-ish on lengthy hwy trips. 65mph or 85 mph didn't seem to matter. If driven in town that number was about 14. 3.42 axle ratio, I have a 3.73 I pulled from a salvage and if this one ever has issues I'll swap. Not for mpg but a little better performance.

[Leeann_93]

With my AWD vans, the absolute best mileage I ever saw, with 89 octane, no cargo or third row seat, flat roads and 75 mph highway driving, was 20.1. Once. In my '02.

I generally get 17.5-19.2 on all-highway runs. All mine have 3.42 gears and get better mileage at 75 than anywhere between 55-70 - and have better power, too.

I used to get 20-21.5 mpg in my '93 Olds Bravada, same engine and AWD system as my '93 Astro, with 3.73 gears and G80. But that's a smaller, more aerodynamic vehicle than the Astro and a little bit lighter.

[95SafariRunner]

Nice Safari you have there. Far as milage I would say that's about it. Do you know the rear end ratio? Those saying 23 mpg+ I find that hard to believe. If your already going to put the headers on then free up the rest of the exhaust system as well. Have you replaced cap and rotor, plug wires, plugs, air and fuel filters?

Honestly I have no idea what the rear end gearing is, but yeah a cheap pair of headers should improve it a bittt, we'll see! Also yes, when I first got the van, I did a full tune up, except a fuel filter!! I only recently learned about those honestly..

[95SafariRunner]

I'd say that's going to be your gas mileage. That's about average for these vans. But, more importantly I'd like to ask more specifics on that push bumper you have there. Please.

As for everyone asking about the bullbar! Thank you for noticing, not much I can say about it though, I picked it up for $50 on facebook marketplace.. supposed to fit an early 90's dodge, but I'm a welder with too much time, and made it fit!

[MI_Ghost]

I'm one of those that can document 24-25 mpg. @ 65 mph of course!
The biggest change I noticed was when the distance driven changed. I went from a 22 mile drive to 87 mile drive and my mpg changed from the normal 19 mpg to 24 mpg.

One thing you will find is idling and acceleration are your 2 biggest mpg killers. Followed closely by weight.

Some of the changes I have made.
Handling: No more drunken sailor!
KYB Gas shocks.
Front & Rear sway bars. This very noticeably helps the handling allowing me to carry more speed on some ramps that I used to slow down considerably for. I have a couple long sweeping ramps that were 45-50 mph ramps that I do not kick the cruise off for anymore. End result is less hard acceleration to get back up to speed.

Engine upgrades done as maintenance/durability improvements
High power ignition coil - MSD 40K volts compared to stock 20K volts
Aluminum distributor
Upgraded injector - 03-05 real injector

Still planning on adding the MSD ignition box

Driving style as much mechanical modifications will affect your mpg.

[AstroWill]

So I'm here asking for advice, to get the best MPG and best HWY cruising speed. As previously stated, I get 19mpg HWY,
What would y'all say to change for better MPGs?

That is decent mileage for our bricksvans. There are so many factors that affect fuel mileage. Technique is probably the biggest factor and it's free to change. Keeping up on maintenance(filters/plugs/sensors/etc), lowering, ground effects/air dam, tires(size, type and brand), terrain, high tops, weight, roof racks, gearing, speed, smart use of A/C, etc all make a slight difference.

Also side note, I busted a bolt off the stock cast iron exhaust manifold, and I'm replacing them with a lighter, cheap pair of headers, and maybe a cat delete. Hoping that will improve performance on the 4.3L? Maybe? Better air flow?

Engine is an air pump, anything that improves flow will help a little. Removing/changing your cat isn't going to give you noticeable gains unless it's plugged. There are cheap universal high flow cats that can easily be welded in place.

[Ironsides]

Welcome.
That's good mileage, I used to get 20-24 empty before lift and larger tires at 65-55. I'm always loaded anymore and 15mpg isn't bad, it's the lift, headwinds, hills and trailer killing me, down to 10 at times but I'm always 65-75.
I like your grille guard too.

[95SafariRunner]

Welcome.
That's good mileage, I used to get 20-24 empty before lift and larger tires at 65-55. I'm always loaded anymore and 15mpg isn't bad, it's the lift, headwinds, hills and trailer killing me, down to 10 at times but I'm always 65-75.
I like your grille guard too.

I wont lie, the van is more of a 10 footer!
Looks real good from 10ft away
Also see I'd like to just break 20mpg... atleast, I dont know..



Another side note, does anyone on here know how to tune an OBD1 system? I cant find any information on the subject.. I have vehicles that are OB2, and you can just plugin and tune with the right computer software, but, again, my van is a 95, on OBD1

[AstroWill]

I wont lie, the van is more of a 10 footer!
Looks real good from 10ft away
Also see I'd like to just break 20mpg... atleast, I dont know..

Just make sure all of your trips are downhill

Another side note, does anyone on here know how to tune an OBD1 system? I cant find any information on the subject.. I have vehicles that are OB2, and you can just plugin and tune with the right computer software, but, again, my van is a 95, on OBD1

You have to burn chips for it as they didn't have re-programmable chips. There used to be a bunch of sites that were really good, but everyone has kinda moved on.