Big tank looking to save gas
 

Hey y'all, I got a 1994 Chevy Suburban weighing in at 6500lbs. It has a 350 V8 5.7L engine, and a stock 4spd. .70 4th gear O/D transmission. 3.42 differential gears (looking for 4.10). I live in the mountains/hills of PA. currently im getting 10 city and 15 highway roughly.

Sounds like you're getting exactly as you should... Those vehicles aren't exactly fuel efficient. With the money saved, why don't you just buy another vehicle and use that as the commuter? As for fuel saving ideas, the only thing that I've found unequivocally improves mileage is to air up the tires. I think airing up the tires on an SUV to sidewall pressure has a far more profound effect than on a car, but that's just my experience.

With that said, drive with extra caution as handling characteristics may change and in the case of my truck, I believe I found it to be a bit more tipsy than before but then again, at the speed I was taking some turns, if I did crash I'd most certainly be my fault. It became a non issue when I toned down how fast I was going around certain corners. As for other ideas to improve mileage, check around the site a bit more or go to ecomodder.org and you'll find a laundry list of ideas to improve your mileage like increasing intake temperature, grill block, etc.. Anyhow, the suburban is so heavy and inefficient that it's pretty much a lost cause. Remind me why you can't make do with a car?

well ive considered buying a second vehicle, but at the time I just cant afford two vehicles (insurance, maintenance, etc) maybe after college... anyway, I live on a farm, and do heavy towing and hauling. show me a prius that can tow a 30 foot travel trailer. and I also do landscaping and general handyman jobs. so i need a large amount of cargo area to carry my tools. id love a hybrid ford or something, but its just not practical. and Ive thought about vans, but the vans that will give me the power I need wont give me more than just a 1 or 2 mpg gain. and i wont have the amenities of my suburban

Yeah, sometimes a dedicated FE car doesn't pay for itself. Some people just need a truck to do their work reasonably.

I can understand the OP wanting a vehicle that can tow, but the question is, is that ALL the OP is doing? If 90% of what you're spending your time in the truck is towing, then you're pretty much SOL. But if you spend maybe 30% of the time (which is still quite a bit) doing such things, then you'd be best served with a car for the 70% of tasks you do and the 30% can be for the truck. You'd be surprised at the number of things a Corolla can carry in it so unless you're carrying something like a lawn mower, you could still fit that stuff into a Corolla, so long as it has fold down seats. Maybe you could take a snap shot of all the tools you'll need (not want) for a given job.. I mean I know you're probably carrying all the tools you could possibly need but a lot of the time, people carry more than they need just for the sake of convenience and since that suburban has quite a bit of room in the back, I wouldn't be surprised at that fact.

buying a second car is not an option right now. I cant afford two vehicles. insurance, gas, inspection, etc. I just want to know what I can do with my current beast

Well I already told you, what has been said has been said over a thousand times, no point in making a thread about it.

https://ecomodder.com/forum/fuel-econ...ifications.php
https://ecomodder.com/forum/EM-hyperm...ecodriving.php
https://www.gassavers.org/article.php...ps-to-save-gas

None of these are the "miracle" you're looking for but may be enough to make you happy enough with the mileage you get.. Nobody really hypermiles a suburban on this forum so don't expect to see any crazy suburban modifications that boost mileage.

20.6% above EPA in a Sierra full size pickup, which is a Suburban with a little extra length and no rear roof/windows...and I'm barely even trying anymore. I got 30% back when I was making an effort.

Well if he is towing as much as he says he is, it's not likely that he'll be able to make the gains that you've managed to make. But if he isn't towing all that often with the vehicle, then he should go with another vehicle but he strongly insists that he doesn't have the money for it. The only thing I can think of for a person that drives a Suburban but isn't towing that often is if they're a professional landscaper that carries a lawn mower, weed whacker, trash bin, etc etc. inside which can and does happen. But if he just brings some trimmers, and a weedwhacker, then he doesn't need a suburban for that. I don't see why the OP doesn't get like a $500-$1500 beater. Plus he'll get a discount for having a multicar insurance policy. Hey OP, do you live at home with your parents?

hell yeah id love to get a little 500 5 speed dodge shadow or something, but I can barely pay insurance for the one vehicle. if i buy another, ill have two insurance policies, two yearly inspections/emissions, two vehicles to maintain, and ill have to find space in the driveway for the second one. It would be great, but its not just a 500 dollar car, pay the 500 and done. yeah I live at home. what wrong with that. I commute to college. its only 20 miles away. so either pay 6 grand a semester for a dorm, 400 a month for an apartment, or live here with free room and board and free food. cant beat that. after college Ill have some money saved for my own place. but until then, im trying to save every penny I can. And I never said I frequently tow. but when I do, its heavy loads. plus the winters here are ridiculous and the township doesnt know what a snowplow is. so unless you got 4WD or AWD, youre screwed til someone with a private plow decides to run down the road.

and I never said i wanted a "miracle" 90MPG Burb, all Im askin for is just a few small tips. other than the obvious: reduce weight, go easy on the throttle, coast to a stop, draft, windows closed, A/C and Defrost off, proper tire PSI. I was hoping yall could enlighten me on a few other lesser known tricks

Weight reduction probably won't help. You'll need to remove 1000 pounds or more from that vehicle before you can begin to measure a FE increase. You can try, though; it can't hurt.

For lesser known tricks, the biggie is Pulse & Glide aka P&G. That's done by accelerating, putting it in neutral until you're going too slow, then accelerating again. It allows you to reduce the quantity of revolutions of the engine over the course of your trip, so less energy is wasted on engine friction and reciprocating loss. It also allows you to operate your engine in a more efficient range where it's producing more work (search for BSFC to understand that a little better).

P&G techniques vary. I've found that if I pulse uphill and glide down, it is most efficient AND reduces any issue of holding up traffic because my speed is more steady. Other people have found that using gravity assist for their pulse and then doing the minimum required to climb the hill works better for them.

Your truck has the 4L60E transmission which is known for premature failure in heavy applications like trucks. Mine has 192,000 miles on it and is still great, knock on wood. I've been using P&G for almost 20,000 miles without incident. I do rev-match when I go from N->D, which may help. That means I step on the gas so that the engine will be at the correct RPM already when the gear engages, rather than making the transmission force the engine up to the correct RPM.

Understand DFCO (Deceleration Fuel Cut Off) and your truck's DFCO behavior. That's when you're off the gas pedal but still in gear, you're engine-braking, and your PCM completely cuts off fuel injection until either you get down to 1000RPM or you step on the gas pedal. Each vehicle has a complicated set of rules for when it will and won't DFCO; my truck has to be engine brkaing for 8 seconds before it will DFCO. It's pretty worthless in mine. Jay's is more cooperative and he tried very hard to use DFCO as much as possible by downshifting, but that may have contributed to his transmission's early failure. OTOH, it's no more work for the transmisison than if it downshifts because you stepped on the gas, so it should be ok but I wouldn't recommend harsh downshifting either way.

DWL (Driving With Load) is another strategy. I haven't seen any theory supporting it but some people have had results. DWL is when you choose a position for your gas pedal and you hold it there, letting your speed change with terrain.

One modification that might help is an extended air dam. If you can reduce how much air gets under the truck, it may be more aerodynamic.

As a side note, you said you do heavy towing; when you do, you should increase your tire pressure for safety regardless of whether or not you want to save gas.

Yes, there was a period where I tried to induce DFCO as much as possible (by downshifting). After a few months my torque converter failed. The truck was 9 years old with about 150,000 miles on it at the time. I am unsure if all that heavy DFCO lead to my torque converter failure, or was it just time to go anyway. Looking on the bright side, because I was extremely aware of the vehicle's "normal" behavior, and I was very strict on keeping up with my maintenance, I was able to detect this problem before it ended up causing the entire transmission to fail. I do not go to that extreme anymore, but I will still DFCO when going down steep hills, or exit ramps off the highway.

My truck is more cooperative than HC's when it comes to DFCO. My truck will enter DFCO after 3 seconds of RPM>1,500 & Throttle Position = 0. It will stay in DFCO until you either press the accelerator, or RPM<1,000.

The reason why I asked if you were living at home is because then it'll allow me to ask the next question... are you on the same policy as your parents? If you've got auto insurance and you're completely freestanding, expect to pay a lot more especially if you're young than if you just went under the umbrella of your parent's insurance policy. I don't know if you're already doing this but if you're not, you can save a bundle on insurance. Very heavy vehicles have high liability insurance as well because they're a bigger threat to others on the road. If the suburban is not yours, you could maybe assign the vehicle to your parents and then just get yourself your own car while still being able to drive the suburban from time to time. How much are you paying per month, per quarter or per 6 months?

thank you cow for all the tips. ill try it. the truck has a new transmission as of 10k miles ago. truck is under my moms name and on her policy. I changed my plan a bit, so ill have to wait for my next statement to see what exactly it is now. space in the driveway is a huge issue in me getting a spare smaller car. after the weather gets better, they offered to let me drive the Camry. Unfortunately, I dont know how much longer that thing will last. im definitely getting a second vehicle when I get my own place. might try to air dam.

hey, would a slight wind deflector over the rear hatch help any? maybe divert the wind drag a little?

Here's a tricky one, which works best on roads you travel frequently.

Try to get a feel for the timing cycle of each light. Then if you see one turn yellow/red, hit the brakes as soon as quickly as you can to slow as much as possible, so that you:
1) Get to the light exactly when it turns green, and
2) maintain as many MPH as possible.

If you wait too long to brake, you'll have to slow down more, or even stop - but if you hit the brakes early you can hopefully maintain 20-25 MPH when the light turns green.

Obviously this is harder to do when you are not familiar with a traffic light.

-Bob C.

No, but what may work is if you were to fashion a kammback for the rear. That is something on my list of things I would like to eventually do, but I've never gotten around to it.

how would I fashion a kammback? it would render the liftglass useless. when its opened, the glass is above the roof line. got any ideas?

My thoughts were to fashion one that attached to the frame of the rear glass. Last winter my truck was parked nose into the wind during a blizzard. The resulting accumulation of snow on the back glass was a perfect kammback. I wanted to take photos, but my camera was in the back of the truck. I wished I could have taken many pictures & measurements so I could have replicated it.

one idea could be to open the glass to a 10 degree angle (10 degrees down from level) and you could use a piece of 1x1 to hold it in place. you could measure it, cut it, and hold it in place with cotter pins or something. maybe have one on either side for stability.

the down side would be that you may get crap in the bed of the truck because now you have an opening.

all this is assuming you are speaking of a camper shell. you could have the pieces of wood completely removable so you could slide them on the top of the side rails when not in use. I don't know if they are all this way but my dad's old camper shell on his truck had a lip on the side rail so you could put stuff there and it wouldn't fall off (too easily). we used to ride to the beach in the back of the truck when we were little. that is before they came out with the whole "IT MIGHT KILL YOU" thing. and we never had seatbelts back their either. we used to pile up on bean bags. 1 truck + 6 people (mom, dad, 4 kids) = fun and cheap vacation transportation

my truck is a Suburban. not a pickup. didnt think of attaching it to the glass frame. may be interesting. anyone good with photoshop? I think it would look hideous. but who knows, I might be wrong. anyone got any ideas? also, would the kammback help for short hilly driving? or is it mostly a highway mod?

sorry for the confusion.

if yours isn't the one with the barn doors in the back, you could just use some plexiglass and bend your own, use some double sided tape to attach it to the glass and call it a day.

though this isn't a great example, here is one on a metro (but made of coroplast). it is similar to what I am talking about.

https://www.gassavers.org/garage/view/272
https://www.gassavers.org/garage_imag...3zvrib86q.jpeg

if you used plexiglass and used a heat gun to bend it into shape, you could make a similar design and it should be a lot sturdier and a little more eye pleasing.

you could make it out of these materials to start with as they are cheaper (sometimes free) and you could get an idea of the angle and what not.

it does do more with higher speed. the aerodynamics become a large factor at speeds over 55 (as a rule of thumb)

ok, well ill try to draw up a removable design. that way, if I cant stand the look, or if it gets in the way, I can leave it in the barn til I do a long highway trip. ill price some plexiglass or look for some around here