The 35mpg Suburban - Fuel Economy, Hypermiling, EcoModding News and Forum

5EFE · 10-14-2009, 05:32 AM

Wasn't sure where to put this. I suppose Fossil Fuel Free works since it would be running pure vegetable oil.....

I believe it is possible to get not only good, but fantastic mileage out of a Chevrolet Suburban. Last year I bought a 1990 GMC 'Burb with 4WD, a 3 speed TH400 and a 6.2 diesel. Despite being automatic, lifted, massive, heavy and as aerodynamic as a semi, it returned about 20mpg, not bad for three tons of American steel. I've heard of owners getting 22-24mpg. I like the 6.2 because it sounds great, and was built for economy rather than power (only 130hp/240tq). Unfortunately that truck caught fire and was sold for scrap, putting my dream of a WVO burner on hold for a year.

Anyways....... one day I would like to get another and: install 5 speed (a rare factory option) lower it as much as possible, change rear axle to lowest availible ratio, make a full belly pan, gut interior completely, remove 40 gallon fuel tank and replace with internal plastic 35 gallon tank, headers, maybe a Banks turbo (another factory option). With these mods and the other usuals I don't think that 35mpg is out of reach, who knows maybe even 45 could be done on a long stretch of Utah road.

Does anyone here have any hypermilling success stories with the 6.2 or any other V8?

CoastRider · 10-14-2009, 09:05 AM

I dont think that is unreasonable. My F150 crept up to 30 mpg on a recent trip.

shovel · 10-14-2009, 10:42 AM

er...

if you're going to lower, regear, and gut a suburban... it's not really a suburban anymore so much as a suburban-shaped, suburban-sized little crappy car.

So just start with a crappy little car and then you won't have to do any work at all to see 35+ mpg.

roflwaffle · 10-14-2009, 04:33 PM

Quote:

Originally Posted by shovel

er...

if you're going to lower, regear, and gut a suburban... it's not really a suburban anymore so much as a suburban-shaped, suburban-sized little crappy car.

That can tow/haul way more than any little crappy car ever could...

Edit - This should probably be in ot-tech, since a conversion should still use diesel for start-up. VO needs to be heated before safe use.

4more · 10-14-2009, 05:23 PM

i like the idea, a friend of mine has a newer 2wd dually w/ duramax and 5 speed he can get over 20 highway pulling a 24 foot enclosed trailer and just the truck has been real close to 30. he is another example that mpg hobbest or what ever we are called can drive a big truck too he drives for a living so every cent he saves is a good thing

rmay635703 · 10-14-2009, 06:03 PM

I drove 6.2's all my life until recently.

Anyway with 2.73 gears and a crappy 700r4 I was topping 26mph driving around 60-70mph in an 89 diesel sub Sadly that transmission cannot handle those gears and that truck is just sitting out at the repo depot waiting for me to find a blasted diesel bell housing and NV3500 5sp.

My fathers 350 93 Suburban has gotten over 24mpg with a generator off the back and loaded to the ceiling with crafts. Sadly that motor had a mishap at 180k, and despite being fixed gets crap MPG now but it was good for years typically in the 18-22mpg area.

And my old favorite 82 diesel sub w/ a 3sp auto always delivered 20mpg even in the winter in town or highway. Sadly that one rusted to pieces to the point the doors wouldn't work anymore.

The best place to get info on what you want is to visit the diesel place forums and the diesel page forums, both have a wealth of info on just exactly what you want to accomplish.

A word of warning though, you better be able to install everything yourself since no one is willing to install a manual into an auto these days and finding the blasted diesel bell housing up here in Wisconsin seems to be impossible for some reason.

Good Luck
Ryan

5EFE · 10-17-2009, 03:13 AM

Quote:

Originally Posted by rmay635703

no one is willing to install a manual into an auto these days

Why is that? I figured I would need to educate myself on conversions first anyway to save money and make sure it was done right.

vpoppv · 10-17-2009, 12:27 PM

Quote:

Originally Posted by 5EFE

Why is that? I figured I would need to educate myself on conversions first anyway to save money and make sure it was done right.

I know nothing about Suburbans, but the topic comes up frequently in the Geo Metro forums. The problems associated with installing a manual into a car setup for auto are difficult. You need to make the motor mounts work, you need to add the pedals, and the ecm needs to be changed out. Not a task for the faint of heart. Personally, I'd rather convert to electric than putting a 5-speed in an auto

.....

rmay635703 · 10-18-2009, 03:12 PM

Quote:

Originally Posted by vpoppv

I know nothing about Suburbans, but the topic comes up frequently in the Geo Metro forums. The problems associated with installing a manual into a car setup for auto are difficult. You need to make the motor mounts work, you need to add the pedals, and the ecm needs to be changed out. Not a task for the faint of heart. Personally, I'd rather convert to electric than putting a 5-speed in an auto

.....

It really isn't THAT difficult, on a suburban (at least the 6.2's) didn't have an ECM, they didn't have to have the motor mounts changed, even the driveshaft didn't have to be touched since an NV3500 is a drop in replacement for the 700r4 that most have. Mechs just aren't interested in doing any real work anymore, they want a 15 minute job like changing glowplugs on the jetta then charge $900 for it saying it took so long.

The issues with the suburban to manual swap are with 1 crossmember (only on certain years) and with getting the pedal & shifter/link to fit which are machining issues.