Hi, you are all probally bored to tears with my request, but what modifications can I make to a new 2008 Chevy Silverado 2500 HD that will legitimately increase my MPG - even just 1 or 2 MPG.
Please don't get too down on me for my choice of vehicles. My other car is a Subaru. The truck will only be driven when our needs require it. Probally will only put 4-7,000 miles on it any given year. We need a 3/4 ton truck, that is the bottom line. I would have gotten a hybrid 1/2 ton but it will not suffice. A deisel engine is not a good choice for our high altitude, very cold climate (often -34 in winter when starting vehicle, many weeks -20). There is no biodiesel available and pure vegi oil is not a viable option here.
I already employ the basic fuel economy recommendations and I ride my bike almost exclusively. (I can ride my bike to work and to run all my errands). I even have studded snow tires on the bike so I can get to ride in the winter when we have 4-5" of packed on the roads for 5 months of year. (At least for now).
I have been reading and looking at the various aftermarket products that one can add to their vehicle and am interseted in which of these are valid. Any comments, suggetions, advice etc is greatly appreciated.
poof well, when its gonan be that cold and snowy and slippery, i dont think much of anyhting is gonna help FE. pumping the tires up will help, and just driving and accelerating slow will help you the most i would think. is it manual or automatic? if its manual i would say coastign would help alot, auto i dont know if it would be such a good idea to be coasting then dump it into gear while on snow...never tried it so i cant say.
The appropriate mods would depend on the type of driving you do (low speed around town or high speed in rural areas and freeways). For both types of driving; raising tire pressure up to max sidewall pressure (less rollng resistance), use the lowest weight motor and transmission oils allowed by your owner's manual (less engine/transmission friction losses), grill block (less aero drag and faster engine warmup),and employ the hypermiling driving techniques as discussed on this forum and at Cleanmpg.com.
For high speed driving, reducing aero drag is most important. How far you can go with it depends on what you use your truck for. You can start with underbody panelling (which can double as skid plates), smooth hub caps, rear wheel skirts, as these mods can reduce drag without adversely affecting the truck's utility. There are other aero mods (specially shaped bed covers, reshaped front end, etc) you could add to your truck to improve mileage but, depending on what you use the truck for, they could affect its utility to some degree. Take a look at pics of Phil Knox's Toyota T100 for ideas on extreme aero for trucks.
...what modifications can I make to a new 2008 Chevy Silverado 2500 HD that will legitimately increase my MPG - even just 1 or 2 MPG.
A tonneau box cover will give immediate improvement at highway speed. Depending on your road conditions and hauling needs you might be able to use low rolling resistance narrower tires pumped to the side wall max, what tires are on the truck now? When you're not towing or hauling heavy loads you can blank off much of the grill in front of the radiator, or just hanging some screen material in front of the rad to keep bugs from plugging the vanes and to minimize rock damage so that your clutch fan is not kicking in as often helps. You probably don't have an electric radiator fan so you might consider one of those, a speed shop can set you up. If you don't do any towing you can get by with smaller side mirrors for some improvement at highway speeds. Some lightweight aluminum full length skid plates such as for 4x4 use can help smooth out the underside of the truck.
Using OEM specified lubricant grades but of a higher quality with an ester base component in the diff and engine will help, Redline, Amsoil, Motul, etc. If the truck doesn't have an instantaneous mpg readout a Scanguage2 that plugs into the OBD2 port will immediately show what the improvement in fuel economy is when driving 60mph instead of 65, or what the saving is for slow climbing a hill. Talking to a speed shop might give some ideas as they will have things like undersized pulleys for various components running off the fanbelt which can reduce parasitic engine drag, but most of those guys will first try to sell you on expensive intake mods and cat-back exhausts which won't help you at all in terms of economy.
Rather than taking someones word from a forum you'll want to research each improvement that can be done to determine if it will work in your application imo, but for something around a $1000 investment you could get your truck to 25 or better mpg I think, which is only a few percent above EPA ratings. Somewhere I've read that by 2011 OEM's will need to provide 30 mpg gasoline light trucks, but I had a 30 mpg or better truck 40 years ago although not to current emission standards.
Are you towing something heavy all the time with it?
Put 10% taller, but thinner tires on the rear. This will probably set off an error for ABS, but I think it would still work. If you don't want any ABS problem, then put equally taller tires on the front. Inflate as to max safe level.
Obviously you'll need to make sure you have clearance.
This effectively would change the gear ratio by 10%.
Since its a GM, a Hot Air Intake with a cold air flap that would open by pulling a manual choke cable might work to get you power when needed and efficiency when not. Instead of cutting up the original airbox, get an extra one to modify and swap it back to stock when you take it in for any warranty repairs.
When you change fluids, switch to as thin of synthetics you can get away with and keep the oil 1/2 qt low, but with a bigger filter.
As suggested above, reducing wind drag in the bed somehow should be up on your list.
I'm fairly sure that the 2500 HD is a 4x4 so you would need to keep the tires the same size on each corner, but as Bob says you may be able to go a size taller, look for LRR tires that have less revolutions per mile, the ones you have on now are likely about 685 revs/mile look for about 635 to 650. Several other things you could do is if it has automatic front hubs change those to manual, install air deflectors in front of each tire and modify the springs to lower the body from 2 to 4 inches. You could also look for the lightest weight LRR tires, lighter aluminum wheels if yours are steel and an aluminum rear drive shaft for some weight savings.
Have your dealership check the alignment as that can often be incorrect from the factory, and have them check for abnormal brake drag at the same time. Depending on your hauling needs you might even be able to source a factory look lightweight fiberglass box to replace the factory steel, as well as an aluminum rear bumper for some good weight savings. You might also look at the need to carry a spare tire.
You might even look at an electronic fuel cut-off governor to force you to keep the speed under a set limit, depending on hills in your drive.
Just reread your original post, definitely look at Motul Gear 300 75W90 differential oil, good to about -55C, I'd do some UOA's to confirm iron wear but if you have limited slip diffs you'll need to use thicker synthetic gear oils, Mobil 1, etc.