suburban gas mileage

[freighttrain50]

i have a 99 suburban and if the gas mileage is bad enough it seems to be going down. i used to get around 18-20 on the highway and now that has dropped to around 15 or so. what can i do to get it back into the upper teens? i have heard of changing air filters to a K&N filter, heard that is supposed to help. Also i have heard of changing spark plugs and changing to a hotter burning one like the Bosch Platinum +4. Anybody use these? If i put in hotter burning plugs will it damage anything because of the hotter temps. anything would help, i can get anything for real cheap because of the fact i work at the Napa Distibution Center a few days a week when i'm not at school. THanks for the help.

Train

[rangr]

Freight, before trying to much, everybodys gas milage drops a little in the winter. Gas has alot more additives in it in the winter not to mention water in the gas from condensation. A k&n air filter certianly cant hurt your fuel milage but for what they cost I dont think it would pay for it self anytime soon. I have a work truck that is a diesel that get alot of miles in the winter I may lose as much as 5 miles to the gallon.

[upnorth]

I wouldn't put hotter plugs in it unless it is not firing well, you could scorch the tops of your pistons. I would try new plugs and plug wires though. I got 2 or 3 more mpg when I did that on my ranger.

[freighttrain50]

thanks for the info guys. you would be amazed at the markup on parts though. i just put in new brake pads on the suburban that would normally cost around 93 bucks where as i got them for a third of that for working there. i'm sure that air filter can't be that much with my little discount.

[Jeremy airjer W]

How many miles do you have on the suburban?

If you put the Bosh Platinums in I gaurantee it wont start in the cold.in fact they don't work well in Gm's, Ford's, and Chrysler's in general. Stick with the O.E. A/c delco platnums (I think they are platnums). You will get the best performance/mileage with them. If the Bosch plugs were better they would come straight from the factory with them. The Manufacturers want there cars to run the best on the showroom floor, right? I always like making the phone calls to tell the customers that those nice new Bosch plugs that they spent a couple hours replacing, not to mention paying a premium at the counter for, are the reason why there vehicle won't start!

by the way my truck gets 26-27 in the summer and 22-23 in the winter.

[Macgyver55]

freighttrain50,

You haven't said anything about how many miles it has or if you have done anything to it yet. Any vehicle will lose some mileage due to wear and tear and age of parts over time, but a significant drop can indicate a problem. Also winter will take a toll on mileage and you can expect to gain some back when it warms up. Fluids are thicker in the gear train, grease is thicker in wheel bearings and pretty much everything is more stiff in the cold.

Aside from that, if it has 100,000 miles or more it should have had plugs, plug wires and a cap and rotor by now. (If it is a 5.7) A 5.3 wont have cap and rotor. In addition you should make sure it has a clean fuel filter. A fuel pressure regulator can cause a change in mileage but there would be other indicators like increased cranking when starting, but is not an uncommon problem on this type vehicle.

Most of the aftermarket items for increasing mileage will give minimal increases at best. Many times the increases could probably be attributed to changing driving habits because you are paying attention to mileage. Stick with OEM parts whenever possible. More times than not they will give you the best return on your money in terms of performance and longevity.

The easiest way to get somewhat better mileage is to keep your tires up to pressure (the most commonly overlooked) avoid fast starts, use cruise control when possible and avoid long warmups before driving. A few minutes is all thats necessary but lots of people run vehicles 10 minutes or more in the winter to get heat before driving. This uses a lot of fuel that doesn't get accounted for in mileage keeping.

[gspman]

I could also be that your injectors aren't functioning as well anymore. I had a service technician (that'd be a mechanic in the old days) who did some work on my '99 Suburban tell me that for those engines GM recommends adding an injector cleaner to your gas every 3,000 miles. He said they recommended something called Chevron Techron. I used this and it seemed to up my mileage a bit. I got just over 15 the last time I checked which is good for my kind of driving in the winter. Also this guy did not sell this stuff at his shop so he wasn't trying to make money off me. It's worth a try.

[freighttrain50]

thanks for the help guys. there's about 82,000 on it.

[Jeremy airjer W]

Wasting money on snake oil gspman!

[gspman]

Airjer,

So is all that fuel tank additive stuff junk or just some stuff? Is there anything to keep your injectors working or do they just slowly wear out no matter what you do? One thing I ain't is an engine expert. But if there's anything I can do to make things last longer on my engine and it doesn't cost too much then I'm willing to try it.

gspman

[Macgyver55]

Oxygenated fuel has been shown to cause more deposits and build up on injectors than non-oxygenated fuel. Although I don't think it is necessary to regularly run injector cleaner in vehicles, a clogged or dirty injector can, and many times will respond to cleaning. Even if you don't have an injector problem now, running a can of cleaner through a couple or even a few times a year may prevent a future problem and certainly won't hurt, and Techron is a good one.

[ChuckN]

I disagree airjr. gspman, I think your mechanic knows something.

My friend is the best car mechanic I have ever dealt seen. He found this GM Techron additive has saved many GM cars from coming to his shop in the last 6 months. The most issues have been with the 3.8L V6 model engines being the most sensitive, popular in the Buick Park Avenues, etc..

There is something goofy with the fuel these days that is messing with the injectors and sending lots of "check engine" alarms to the drivers. The Techron bottle to a gas tank has cured almost every issue and he recommends using it every oil change too.

I've read countless research of how these oil companies are making gazilions of dollars turning less demanded heavier crude oil into gasoline (buying cheap and selling high). I honestly feel our fuel is not as good in quality compared to over a year ago with our fuel issues around the world.

Just my $.02

[Valv]

Absolutely not true about Bosch plugs. I had a '99 Dodge Ram, which while in warranty with 10,000 miles kept fouling stock plugs. I finally replaced them myself with standard Bosch Platinum and never had any problem since I sold truck at 115,000 miles. I also gained 2 to 3 mpg on fuel economy.

I run them on my Jimmy 4.3, Jeep Grand Cherokee, and Camaro, and I definitely improved mileage and performance on all 3 cars.

Dealers have to install parts that agree with warranty contracts from manufacturers, and they don't want to spend $ 2.50 on a plug when they can get away with a $.75.

Get injectors cleaned professionally, a new good set of plugs and tune up ignition, it will do a lot of good to your truck. Neglect is the largest problem on vehicles.

[ice_shack]

I've got an old friend that worked on cars for more than 40 years. He was one of the best Cadillac mechanics in the twin cities. He swears by Seafoam, use it twice a year. Works good in small engines to.

[rmh2o]

First of all with cold weather,vehicle idleing,stop and go driving in the city 15 mpg isnt far out of line.Here is a few things I would check or do first.Replace air filter if dirty (myself wouldnt spend the money on K@N)Make sure tires are properly inflated.Open hood at night and see if you see any archs off plug wires if so you will need plug wires.With that mileage a new set of plugs would be a good idea (I would replace with same plugs)and a gas filter would also be a good idea.I am also a believer in sea foam and use it in everything and run a can to a tank of gas 2-3 times a year.Usually if you have an injector problem it is very noticable,engine missing or running rough.GM does make good injector cleaner that is spendy and has to be pressurized threw the system not dumped in the tank but if your vehicle starts and runs fine I dont think this is your problem.

[Jeremy airjer W]

Valv, Absolutely true about the Bosch plugs. Specifically the platnum plus 4. I've replaced thousands of these for numorous driveability complaints, including the famous crank no start. Next time your in for service (at real garage not a rapid lube) ask them what they think of the Bosch platnums. More than likely they will tell you they are junk.

If my brand new truck was fouling plugs at 10,000 miles and they couldn't fix it, I'd have a different brand new truck siting in my driveway. They obviously had to be missing something!

If you drive a GM use the a/c delco's, Ford-motorcraft/autolites, Dodge-champions, Japanese-ngk, European-bosch. Your vehicles are the exeption as well as others that do run great on them, but why take the chance. It would be great to find out after spending $150 - $200 dollars on a tow and diagnostic charges that your new plugs are the reason your vehicle won't start.

Chuckn, If that was the case wouldn't you think that you would be seeing injector problems on all vehicles made. GM in general has a terrible history with injector failures starting with the first throttle body injectors, then the 2.8 and 3.1 litres then the quad4's then the famous CPI units on the 4.3's then the 3.3 litres (not as common)and then with the new 3.1 and 3.4 litre. I think there might be an engineering issue here. Why don't you see this kind of frequent injector failure with ford (less the mercury villager/nissan quest which are well known for failures)or chrysler, yeah I know the intrepids had leaking injectors and you do see an occasional minivan with a bad one. I cant recall changing any in honda's or toyota's. Every once and a while you will see a honda leaking.

My point is none of the other Manufacturers seem to have the injector problems GM does. I think its poor engineering or build it as cheap as we can rather than the gas in the tanks! I agree that the gas today stinks but I just don't think its the problem!

[BK19]

i use anything but ac delco in my chevy 350 in fact in my race motors i use autolite 145's and they are the best for me

[Wishin2BFishin]

If your truck came with AC Delco parts then that's what you should use for replacment parts. If you are warming the truck up before you drive it then that's most likely where your 3 to 5 MPG are going. Look at your tail pipe, if it's black then your running too rich and something is wrong with the engine or the gas your getting is sub quality. If it's nice and clean then the engine is running correctly and nothing you do is going to make it run better. Air filters were a common cause of bad MPG when engines were carburated. With fuel injected engines a clogged air filter really does not make much of a difference with MPG. Spending big money on these fancy air filters won't help you much. Save your money for some nice new fishing equipment!

[Jeremy airjer W]

Wishin2bfishin, I have something for you to try. Put a brand new air filter in your vehicle and record your MPG after a tank of gas. Then using duct tape, block off a little more than half of the filter (make sure to put the tape on the outside or pleated side of the filter so it doesn't get sucked into the engine). With simular weather and driving conditions I think you might be surprised at how much a dirty filter can change fuel economy, even in a late model fuel injected vehicle.

[lawdog]

Anybody tried those tornadoes? They are supposed to increase gas mileage via better air flow...

For what its worth, I don't buy that Bosch plugs are no good at all! I've run em with decent luck.

[Jeremy airjer W]

lawdog, NO THEY DON'T!Pual Bran (autotalk host 1500 KSTP) gets this question every once in a while and I agree with his Position. Auto manufacturers do everything possible to get every little bit of fuel economy possible out of there vehicles. If they could get 3-5 MPG by using one of these they would be stock on every vehicle made. I think I've also seen a deal on the news where the guy buys stuff to see if it works and it didn't.