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Fuel Mileage Boosting Tricks and Tips that actually Work!

Polar Bear

Well-Known Member
Messages
83
Location
Montreal
Ok, to start off, this thread will be long and exhaustive and broken into several sections.

I am a Certified GM Mechanic and Technical Trainer and a Certified AM General Tech and Offroad instructor. All of the following tips are from my many years of mechanical experience and a whole lot of trial and error on my own personal vehicles! Some stuff worked and lots of stuff was just a plain waste of time and money and plain SUCKED! :whaa:

My focus will be on H2s but most of the info can directly transfer to H3s and some of it can be useful for H1s. I will try and mention specific upgrades that I know work and work well per model.

Hopefully I will be able to help most of you get your Hummers to be far more economical than they are presently. Some stuff is free and simple but most stuff will cost you money. Most stuff anyone competent with a wrench will be able to do in their own driveway but some stuff will need a shop to help out! I will try and post pics whenever possible and I will try and be as specific as possible with the results of my testing. If something works better. I will tell you why. If something sucked, I will tell you why. I will also try and give you a rough pricing for most things, I might be off a bit since I am in Canada and most of you are USA or Over Seas! So if pricing seems high...it might be in Canadian Dollars!

So for the first post, let's start with the basics that anyone can do.

Tire Pressure is far more critical than most people realize. The recommended pressure on the door sticker is a decent starting point but is useless if you are no longer running the exact factory rubber and if you have added any type of gear to your rig. Inside or Out. There is no way to tell you set your tires at this pressure and it will be perfect, Every Hummer is different, every tire and wheel package is different. Now there are formulas to help you calculate what your pressure should be but there is a FAR more effective and precise way to do it since after all, every tire carcass will flex a tad different from another. So our stock H2 tires are 315/75R17 and had a load capacity of 3195lbs @ 50psi and our recommended pressure was 37psi. I currently run Michelin XML 325/85R16 tires which have a load capacity of 5070lbs @70psi and I run them at 30psi front and 25psi rear.

I determined this pressure by doing the following things;

1. Load your Hummer the way it will ride 80% of the time. Make sure your fuel tank is 50% or greater and if you mostly have a passenger make sure they are with you. This will make sure that you are basing your pressure on the load the tire needs to support the majority of the time.

2. Head to your favorite mall parking lot and be sure to bring a portable air compressor and a digital tire pressure gauge. Once you are there, find the straightest section you can drive at least 500ft without having to turn. Once you have located this spot, take some tire crayon or chalk and mark several lines across the tread of each tire. Make sure to extend to the sidewall so you can easily find your marks.

3. Next drive ahead 500ft in a straight line with light throttle and braking. Then back up and do it again...hopefully you can back up in a straight line as well! Once you have done this at least twice, stop and look at your tread.

4. If your tire pressure is perfectly set on all tires the chalk will be worn off completely from tread edge to tread edge...not likely on your first try but hey it could happen!

5. If the chalk is worn on the edges but not in the center, your tire is under inflated and you need to add air and retest. Add air in no more than 5psi increments. Low tire pressure is great offroad to help the tire to conform to obstacles but greatly increases your rolling resistance on asphalt and will accelerate your tire wear.

6. If the chalk is worn in the center but not on the edges, your tire is overinflated and you need to deflate and retest. Remove air in no more than 5psi increments. Too much tire pressure is just as bad as not enough since the tire can no longer conform to the road surface. This will cause irregular wear which will greatly increase your rolling resistance and affect your fuel economy!

7. Keep adjusting your pressures until you get as much of the chalk worn off the tires as possible. Remember to hone your pressure by working your +/- by going 5, 4,3,2 then 1psi increments. This procedure may take about 1 hour but well worth it.

8. Note you should be checking your pressures at least once a month. And btw, don't waste time and money on Nitrogen gas in your tires. Unless you live in the dessert and the arctic at the same time meaning you see a 120F temp swing everyday...you will never notice even a slight difference. Remember the Air we breath is already 78% Nitrogen anyways!

9. Note, your pressures may be different front side to side and front to back. This could happen since each of our trucks are set up different!


Now, some of you are probably saying, this is stupid, but remember we have to start with the basics and work our way up. If overlook the basics it will affect the bigger steps to come!

Tire Pressure can provide up to a 10% increase in mileage.

Stage 1 complete!

Thanks,

Kev
 

Polar Bear

Well-Known Member
Messages
83
Location
Montreal
To continue the subject. Let's look at maintenance next!

Quite often most of us are under maintaining our Hummers. There are so many key things to keep an eye on that sometimes stuff goes overlooked! And yes I know that many of you will object to some of the things that I say, but remember I am trying to help you save money in the long run and get you better fuel economy…Maintenance is a VERY big key to success in this area!

Let's start with Filters;

Air Filters;
Every Hummer has an Air Filter, but when was the last time you checked yours??? Even if you are running mainly of the street, it is still amazing just how dirty they can get. Normally air filters need to be checked or replaced every 10,000miles or a minimum of 1 a year even if you don't do much mileage. A dirty restricted air filter can cost you up to 20% mileage loss, regardless of filter type or design.
For those of your running a Cold-Air Intake...it is easy as opening the hood. For those of us with the stock air box, you will need to remove the cover and inspect it. If you are using standard paper air filters...stop. While a clean paper filter is better than a dirty filter...there are far superior filter medias to consider. Most of the High Flow filters like K&N, Airaid, AEM, etc will improve the engines ability to inhale and provide a slight 5% increase to fuel economy...but they still need to be maintained. These types of filters work great on the H1 and the H3 but actually have the opposite effect on an H2...they will rob you of power and mileage. This is not due to the filter but due to the OEM Airbox design. If you are using a Cold Air intake system…this does not apply. The best filter for the OEM H2 Airbox is the Donaldson Powercore…I have done loads of testing on this and it is the only one that really allows the engine to breath simply because it keeps all the air flowing in the same direction…straight in-line. The High Flow units all block the direct flow and force it up and over. This causes turbulence in the air box and thus your loss of power. I know some of you might debate me on this, but seeing as I have installed and tested over 7 different systems on my H2, I have found which work and which don’t. As well, since I off-road in lots of deep water and mud an exposed filter in the cold air kits while they do flow better…gave me no safety against ingesting water while offroad.
Best Filters for Mileage Gains;

  1. A Clean Air Filter!
  2. A mandrel bent or smooth formed intake tube with a high flow filter.
  3. Stock air box with either a high flow filter or Donaldson Powercore WITH a Snorkel.
I will expand on this way more in the future…but at least this will get you thinking!

Fuel Filters;
Not every Hummer has a Fuel Filter!
All Hummer H1s have a Fuel Filter…some are easy to replace…the Alphas are a pain in the butt!
Only 2003 Hummer H2s have a Fuel Filter.
All 2004-2009 H2s and All 2006-2010 H3s only use the filter sock in the fuel tank.
All engines need clean fuel to work properly and to provide good fuel economy. What most people don’t realize is that fuel filters need to be replaced on the same interval as the air filters, they need to be replaced every 10,000miles or a minimum of 1 a year even if you don't do much mileage. A dirty or blocked fuel filter can cost you 20% loss to fuel economy. The H1s normally tell you when the filter is beyond done…power drops and black smoke starts! So keep that filter clean! It will save you money in fuel and repairs!
Now for those of you that have Hummers that don’t have fuel filters…while you may be thinking, great one less thing to maintain…not quite! I would greatly encourage you to install an inline filter just before your fuel rail. Remember the In-tank filter on the base of the fuel pump is more of a strainer than it is a filter. It is simply designed to prevent larger particles from passing into the fuel pump. It is there to protect your fuel pump NOT your engine. So you might be saying then why don’t the manufacturers install the fuel filters then??? Simple, Cost Down! Remember if you remove every fuel filter off the assembly line that equals a major cost savings, when you also factor in the time to install it and the fuel lines…manufacturers have a major incentive. Every single manufacturer is doing this…Remember they care more about their bottom line than the longevity of your engine. So without a fuel filter…where do all the particles end up…sadly in your fuel injectors! If the fuel injector spray pattern is affected, so is your mileage and performance. Our engines need a fuel mist/vapor for proper combustion, so remember to keep your fuel clean! The fuel pump socks in the fuel tank will eventually crud up and cause reduced fuel pressure and will strain your fuel pump…at least you automatically get a new one when you replace your pump!

Engine Oil and Transmission Filters

Hopefully everyone knows to replace the engine oil filter at every oil change! I have seen many a Honda manual say to replace it only every other oil change…that is stupid! You need to replace it every time you change your engine oil! Otherwise, the old oil in the filter will degrade the new oil you just put in and worse yet, if the oil filter is blocked…the bypass valve opens and then NONE of your oil is filtered!
Don’t buy cheap 2 dollar oil filters…the filter media quite often does not filter fine enough and frequently tears under pressure. Stick with High Quality oil filters, like K&N etc. Dirty oil robs you of power and mileage and increases the wear in your engine!!
Transmission filters need to be replaced every 60,000miles when you replace your transmission oil. If your transmission oil filter is starting to be restricted your transmission pressure drops…and then eventually so will your transmission! So keep it Clean!


So in other words Change Your Filters and keep the systems they are attached to Happy and Efficient!
 
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SuperBuickGuy

Well-Known Member
Messages
3,403
Location
Woodinville, WA
Tire pressure - I've played the tire pressure game and running 5 psi more than what's recommended tends to get you better mileage. The rub, though, is it wears tires faster so the .1 mpg better economy you get is completely erased because you have to buy tires more often. I ride bicycles, and the incremental game is one we play - a lot. Example, I put ceramic bearings on my bike. Manufacturer said 3-5% less rolling resistance (and of course they don't rust). I had plenty of baselines because I ride with a GPS bike computer and ride the same routes. I got a 5% faster time. Tire pressure, I did the same thing - I went to tubeless, clincher tires. Manufacturer recommended coming down from the 120 psi that I normally run to 90 psi. I lost time. However, I went up to 98 psi and got the same time - point is, what you're saying about tire pressure has validity; but the incremental nature of it all, and air resistance, make gains pretty minimal.

I have utterly the worst possible commute - 10 miles, all in-town (less than 40 mph), stop and go, if I'm not going up, I'm going down so my mpg is what it is (sucky). The best thing I could do for economy is to move to the midwest - but I'm going to do that ;)

What I have found, though, is burning the lowest alcohol content fuel nets me the best gains - even though it means going several miles out of my way to get the fuel.
 

CaseyS

Well-Known Member
Messages
731
Location
Louisiana
You can check rolling resistance on a fixed course. Start at a known speed around 30-40 mph. When you get to a landmark, shift to neutral and coast all the way to a stop. Mark this point. Make changes and repeat the test. You may have to do this at night where there is no traffic to impede. The further you can get your coast, the lower your resistance. This works for aero mods too if you start at a higher speed. Aero mods on a hummer is an oxymoron though.

I played around with hyper miling for awhile and was able to get over 18 in the h3 in stop and go city driving with very disciplined driving and a lot of neutral coasting.
 
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