Need more range - Aux tanks?

[ComputernerdBD]

Hey everyone. So I have been doing quite a bit of traveling involving the Trailblazer since starting a new role at work, having been on several trips from upstate NY to northern VA (350 miles/6 hours). This truck is great on long trips, very comfortable and the right size vehicle for the job especially putting alot of luggage and parts in it. Right now it has around 68k on it.

My only complaint that normally only becomes an issue on longer trips is gas mileage.... I keep it at speed on interstates so on average I get 14-16 mpg on that long stretch (CAI under the hood, high weight in the back and cargo rack on the back doesn't help), meaning I can only get about 4 hours range safely before it needs to stop for a fillup. Last week I spent most of the day working until 9:30PM and then once I was done drove all but the last 50-60 miles of that virtually nonstop overnight (getting home around 3:30-4AM), making it to a small town in NE PA with only 1/8 of a tank left where most of the gas stations were closed, but I was able to find one, fill up and carry on (with some suspicious activity going on in the store, hence another reason why I hate stopping that hour). It was a nice ride even if it was long. Due to the limited places to stop I wanted to get as far as I can with what I had and the rate the gas gauge decided to move once it hit 1/4 meant I slowed it to 55 and monitored fuel flow, trans gear and vacuum (I have Torque with a ton of gauges on a windshield mounted tablet) to keep the usage as low as I can while maintaining speed.

With these trips being more and more commonplace for me, I really would like to investigate the possibility of some mods to make it possible to get in the car at home and not have to stop at all due to gas until I am in VA, or finish work and not have to get out of the car until I make it back to upstate NY, especially on overnight trips. 6 hours I find is easy, 4 used to be my limit. Seeing all the options available for full size diesel pickup trucks putting aux tanks in the bed or replacing the spare tire with a tank made me a bit disappointed with the lack of options for our trucks.

But I was wondering - Is it theoretically possible to build a kit with one or two small removable tanks (like fuel cells or thick marine fuel tanks), inline filters and fuel pumps with a remote control up front to control the transfer in the back adding up to about 12 additional gallons, secured to the floor (in the storage compartment under the floor would be better), connect it to fittings on the sidewall leading to the fuel filler neck (quick disconnect and valves to a "T") and then for the first 2-3 hours after using about 1/8-1/4 of a tank I just run with those refilling the factory tank at the same time as the truck is using the fuel, giving it about 6-7 hours range nonstop? Almost like ferry tanks on a plane or a built in gas station and I just manage the transfer of gas from the aux tanks to prevent the factory tank from overfilling. Then if it is an overnight trip like this I either get safely where I am going or have reserve if I am in the middle of nowhere to get to a safe area. Future trips might even break 400 miles, still would like to do most of that nonstop.

Thoughts on this as a cheap alternative to a diesel conversion or buying a new truck with tanks the size of a jet? Thanks

 

[Ilikemy3s]

i remember reading a post once of someone replacing their 21 gallon tank with a 25 gallon tank from an XL and it worked. You might also have to replace the fuel pump as well.

The MPG seems low to me as I made several trips with the family from New Jersey to Disney in an Envoy XL and averaged 20 highway.

 

[TollKeeper]

I am wondering what gear ratio he is running, it almost sounds like he is running 4.10. On those type of trips, i get anywhere from 18-22 on my Envoy. But I also have the GU6 gears.

 

[Reprise]

I don't know that I'd want gas tank(s) in the cab / passenger areas of an SUV. But that's 'me'. Just having a thermoplastic gas can in the back of the Voy emits more fumes than I care for (and I have a hard time smelling anything, compared to most people.)

The only company I know of that builds gasoline-approved tanks is www.transferflow.com (all others are supposed to be diesel-only). Even so, they're built for pickup trucks, to mount in-bed.

I've seen a couple of places that sell sidemount 'front-of-wheelwell' tanks (single or pairs). That might be an option for what the OP is looking to do. Again, intended for diesel fuel, and made for pickups.

Even at 14mpg, given a tank that requires 20gal 'to fill' (example only, and talking 'refill' cap, not 'stated tank cap', which is always larger) - that's still 280mi before stopping.

The OP may have to adjust like many of us who tow and get single digit MPG do - fill up more frequently (I start planning my refill at 1/2 tank now, after almost running out earlier this summer.)

I know it's not a solution he wants - but he's seen firsthand what happens when using up most of the tank. Another option would be to swap out to a pickup; there are several options available, from bigger underbody tanks, to in-bed tanks that feed via an automatic pump, etc., etc.

Or - and he mentions this - get a diesel. A DMax should easily yield 22mpg on up, depending on load, and a skilled driver* could probably nudge this closer to 30mpg, in non-tow mode. Problem there is the upfront cost of the diesel, and the maintenance. It takes a lonnnng time to make up the acquisition cost in MPG savings.

A cheap solution would be to get a couple of metal gas cans (e.g.; jerry cans). 5-7 gal each. You'll still have to stop & fill manually, but you'll have the fuel, not have to visit a gas station for it (and not have to smell it while driving). And a pair of work gloves, if you think you'll get the odor on your hands when filling. And / or some hand sanitizer.

* By 'skilled driver', I'll humbly refer to my fill up in OH recently when I was driving WI > PA. Since the DIC shows expected MPG based on past activity, I was pleasantly surprised to see "Range 528 mi" pop up on the DIC (by the time I thought to pull out the phone and snap a pic, it had fallen to '525'.) Usually, my around-town driving shows a range of about 340 (?) or so when I fill up.

Yes, I have an XL / EXT with the 25gal tank (real-world, I doubt I can get more than 22gal in), but you get the idea. And I've got the 5.3L and 3.73 gear to go with that 'big' tank. (*and* I have a Limeswap tune in it, as well.)

Guessing someone may call 'BS' on that, so here's the pic (not trying to do a 'humble brag')


Keep your speed to the limit (65mph or lower), learn to adjust your pedal pressure, and keep out of the pedal when climbing smaller hills, and you should see benefits, mpg-wise - especially on the interstate. (Yes, this all goes out the window when towing.)

 

[littleblazer]

I've put 21.5 gallons in my 22 gallon tank... I really push it though.

What year is the truck 02s and some 03s only had a ~19 gallon tank so...

 

[Mooseman]

It may be possible to install an EXT tank but will likely encounter a few issues like the fuel and evap lines to be extended, repositioning of the filler hose, wiring, straps, removal of the spare if it's in the way.

Gearing certainly does affect mileage. Check the options sticker in the glove box. 3.42 would be best for highway, 3.73 so-so but 4.10 would be a killer.
Gearing RPO codes

And the CAI, depending on which one, may actually hurt MPG if it's sucking in hot air. Some little things might help like removing the roof rack cross bars. And it sounds like you're hauling quite a bit of cargo so that doesn't help.

 

[mrrsm]

As frustrating as this problem can be... making any Non-OEM Fuel System Modifications could automatically invalidate your Vehicle Insurance and Black Ball you with other Insurance Agencies if God Forbid... anything went sideways and an accident were to occur... with or without any fire being involved. I'm 100% with @Reprise on the sound idea of just getting 2-3 NATO Approved Steel "Gerry Cans" (NOT any Cans that sport a White Cross formed into the cans ...as those are STRICTLY made for transporting Water).

Amazon offered these a few years ago and I have them Moth-Balled in the Garage for anything that happens around here and we have to bail from Florida in a Non-Stop effort to leave the state. This is the Link that might persuade you to use "The KISS Principle" and save yourself from a cascade of grief by having these on hand and topped off-sealed up just before you leave. You can always refuel at a Rest Stop by parking well away from the new arrivals and then head right back out onto the highway with peace of mind that your Gas Tank will not be on Fumes:

https://www.amazon.com/dp/B011AJF0PE/?tag=gmtnation-20



One Last Safety Suggestion:

When Gasoline Fumes get exposed to ambient air... the octanes will not only easily evaporate... but release a substantial amount of Carbon Monoxide (CO) into the Air ...WITHOUT the necessity of being Burned or accidentally getting ignited by sparks, lighters, lit cigarettes or short circuits inside of the vehicle. This obvious hazard would strongly suggest in NOT using any Cheap, Unapproved Lawn Mower Style Gasoline Containers... or traveling a long distance with all of the vehicle windows rolled up tight.

Having a functional, tested CO Monitor inside of the Cab of the Truck or SUV is a MUST and will alert the occupants to the presence of any CO and prevent them from falling asleep while driving... or dying from CO Suffocation in a Parked, Running Vehicle with the windows closed for Cold Weather.... while "Resting".

I have investigated enough of these kinds of deaths first hand to know that everyone looks peacefully sound asleep inside of these places using Kerosene Heaters and in vehicles as decribed... all showing the tell-tale signs of CO Suffcoation: Reddish- Pink Noses, Ears and Cheeks... all caused by inhaling enough CO to cause their Hemoglobin to grab the CO Molecules instead of useful O2... and turning their complexions a "Deathly Pink" ...never to wake up again.

 

[Mike534x]

Yes, I have an XL / EXT with the 25gal tank (real-world, I doubt I can get more than 22gal in), but you get the idea. And I've got the 5.3L and 3.73 gear to go with that 'big' tank. (*and* I have a Limeswap tune in it, as well.)

Guessing someone may call 'BS' on that, so here's the pic (not trying to do a 'humble brag')
View attachment 86515

Keep your speed to the limit (65mph or lower), learn to adjust your pedal pressure, and keep out of the pedal when climbing smaller hills, and you should see benefits, mpg-wise - especially on the interstate. (Yes, this all goes out the window when towing.)

You have my old TB Ext with the 5.3 w/3.73 gears beat by 22 miles, I would always get about 503 on fill up after long distance highway driving, and that was with DoD active. Usually did 65, minus giving it gas to get around "slow" drivers hogging the lane. On a good day, I can get about 325 on the Envoy, while other days I can get about 373 to 425 at fill up. Lately with all the city driving I'm doing I see about 240.

When I had my 02 Envoy, it would consistently get 232 miles on fill up, even after doing highway driving (did the math and got about 19-20 mpg). I "think" it may have had the 19 gal tank, almost positive it was 22 but my memory is sketchy. It definitely was one of the "first" batches with a March/April 01 build date.

 

[HARDTRAILZ]

I would definitely just go the jerry can route, but I have ditched all the metal ones. Get some of the modern plastic military or knockoff military ones. Ethanol in modern fuel kills the lining in metal ones and contaminates the fuel. Also you eventually deal with rust. I do not use any nozzle with mine though and use a shaker siphon so its simple and effective
https://www.amazon.com/dp/B072LN1T1W/?tag=gmtnation-20