Here's A Challenge for Ya
 

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. selling the truck is not an option (live on a farm, landscaper, handyman) the truck is a necessary tool. but I really want to get better MPG. any tips please? I want to keep the truck functional as well. and Im a college student, so money is tight. thanks!

Welcome. There's a few of us here with similar vehicles. Jay has a 1998 GMC Sierra 1500 and I have a 2002. Is 6500 pounds the GVWR of your truck or the curb weight? If that's the curb weight it must be a 2500 or 3500.

Mainly we get some decent FE (fuel economy) from adjusting our driving techniques. There are few modifications that can help and almost none that will ever pay for themselves. The first and easiest you can start with is tire inflation. GM probably specified 35psi if it's a 1500. You can definitely go way higher than that without causing a rough ride, bad handling, or bad tire wear. However, on the farm's mud higher pressure would make it more likely to get stuck.

After that it's all about driving style. You may want to keep your 3.42 gears. Putting in new gears is expensive even if you DIY; you may or may not save gas at all, but they almost certainly won't pay off. Usually taller gears will save gas but in your case, living in the mountains, it could go either way.

What kind of driving do you usually do - highway or local?

-BC

I do mostly town driving. short (30 miles or less) trips. many hills. I have my tires a 35PSI. and I drive with very easy accelerations and decellerations. I dont know the exact curb weight of my truck. I was told it was 6500. the door sticker is worn, so until I get a new one printed, I do not know. its a 1500 4WD. I dont carry around much extra weight either

Hi Countryboy,
- If there's one modification that most likely will pay off for itself:
an engine block heater.
It's especially interesting if you do a lot of short distance driving (like you do) and if your average wintertemps are really low.
But all depends on the price you pay a block heater for your car (if one exists at all, I don't know).
- Worth a trial in wintertime: (partial) grill block.
Succes !

6500 is probably your Gross Vehicle Weight Rating, then; that's as much as it can legally weigh when fully loaded. Curb weight is how much it weighs unloaded; that's probably closer to 5000.

You may want to try accelerating a little bit more aggressively. Both Jay's and my truck do better if we don't baby the acceleration too much.

For deceleration, it doesn't matter how hard you brake; the important part is that you should have just gone slower in the first place so you would not have needed to brake at all. Obviously that kind of planning is only possible sometimes. However, as soon as you know you'll need to slow or stop, you should get off the gas pedal - there's no sense continuing to burn gas when you know you'll need to stop anyway.

If you see a red light off in the distance and you know that slowing down from 40mph to 20mph means you can cruise through at 20mph, do so. Having to accelerate from 0 to 40 uses a whole lot more gas than from 20 to 40.

What size are your tires? My truck has 245-75-16. I run 70 or more PSI. My ride is comfortable, my handling is great, and my tire wear is almost perfect (definitely better than it was at 35). My truck is probably a little lighter than yours. If your tires are a similar size or smaller and load range E rated, you can probably go to 70psi or more. If they're a little larger you're probably still good for 50 or 60.

same size tires as yours. I already coast to stops as much as possible. Im leaving the tires at 35. the handling is fine. and at 40 or more, i noticed more wear in the center bar. not risking having to replace my tires before theyre totally used

HC has made some good points. If you drive one of these trucks like there's an egg behind the accelerator you actually get worse mileage. I have the same engine in my truck, and 90% of my driving is short trip city. I've tried mods, the only one that I had marginal success with was a grille block, but then I had to watch my temperatures closely. The grille block is currently removed, but I think I will eventually replace it with a warm air intake. I have E rated tires on my truck, and I love that I can haul more in the truck, but as far as increased mileage, I don't think so.

As far as driving goes, when I'm working my hardest to boost my mileage I shut the truck off at traffic lights, and when I accelerate I go about 20% - 40% throttle, and get to a higher gear quicker. Coast up to stops as much as possible. The really good news about having a 350 is that the air conditioning has a negligible effect on mileage. The truck gets better mileage with the A/C on, then A/C off with the windows down.

Wait! Nobody has done a required post in this situation!

*deep breath*
Don't drive the truck at all buy a beater econobox and drive that you shouldn't ever be driving that except on the rare drives where you actually are hauling something that requires the capacity or better yet rent a truck when you need the hauling capacity yadda yadda yadda we don't like your kind around here on gas-savers.org!
*pant pant*


Okay. Now that that's over with...

With the stock gearset in that, if you're unable to go through the mountains without constantly popping in and out of overdrive, why not just put it in drive in that situation?

I know that darn near everyone I've talked to or read about who's put in 4.10 gears has talked about "Acceleration is amazing, but it killed my mileage, but who cares? It's so much faster!"

Every one has mentioned killing their mileage, so probably not the best idea. Leave it out of overdrive when you're in the mountains, (But only in the ones bad enough it wants to cycle in and out of overdrive anyway) that way when you're on more level ground, you can take advantage of the lower rpm.

how bout A/C off, windows closed? lol. ill have to try to crush the egg this time. just filled up a few days ago, so I can check my mileage with using your tips. now as for warm air intake, I just flipped the air cleaner lid to allow more air in, and I removed the hose that goes from the fender intake to the snorkel. that way its surrounded my engine heated air. is that an ok intake? or can I do better?