Tried Acetone and a Tune Up - No Change In Gas Mileage...

I have a 97 with a 4.3 L. I have owned it for about 2 months. I bought it at 67k and it now has 70K miles on it. I noticed I was getting around 14.5-15 mpg with town driving and 19-19.5 mpg when on the highway. I did a tune up for good measure. New K&N filter, plugs, PCV valve, and fuel line filter just to be safe. I also started adding acetone to my gas at 3oz/10 gallons and my tire pressure is good as well.

Since doing all of this I have not seen any real increase in my mileage. Today it was still 19 on the highway. I don't drive hard and on the highway I travel from 65-68 mph @ 22-2300 RPM. I guess this mileage isn't bad but after seeing some of the others on here who are getting 17 in town and 23-24 on the highway I thought I may be able to get close to that as well. Does anyone have any other ideas to try?

You can expect your Bravada to get a little worse gas mileage than Blazers, due to your AWD. The specified fuel economy for yours is 16 city and 21 highway.

Have you replaced the cap and rotor?
Where does your temperature gauge read when the engine is warmed up?

Switching to synthetic oils in the crankcase and differentials will net you a few extra MPG/per tank. Also make sure that your fuel filter is changed often (Every two years at the most) and that your fuel injection system is up to snuff. In anotehr thread, I advised someone to try an SUV sized bottle of Techron about 500 miles before your next oil change. Keeping injectors, valves and your engine clean goes a long way to getting optimal mileage. Make sure that when you do a tune up, it also includes new OEM wires, properly gapped plugs (.065 I think is what you need for your truck - someone will correct me I am sure), new distributor cap and rotor too.

Come on Wolfox you have the 28mpg blazer you should be able to give him a recipe so he can have 24 in the awd bravada.

Alas, I also had an AWD Subaru that all I could get out of it was about 35MPG. AWD systems present a small amount of calibrated drag on the driveline. This is done by slightly differing gear ratios from front to rear drive axles. At least, this is how it worked in my Subaru. Usually, in perfectly dry conditions, the torque split was 90-10 from front to rear, making it drive like a FWD car almost all of the time. However, the slight bit of drag that eats into the fuel economy brings the viscous clutch fluids in the center differential up to an "operating temperature". When the wheels slip on either side of that differental, fluid temperature rises and then "locks" the differential so the torque split changes, engaging rather than letting the center differential "slip". This makes it work like a 4x4 at that point, spliting the torque nearly evenly from front to rear. However, this process and the very nature of the system makes the rear wheels essentially "drag" just a little bit on these cars/AWD systems, and there is where the fuel economy hit happens. So we're working against, IMO, an engineered in "loss" that we may not be able to easily overcome.

Sticking to quality synthetics wherever possible helps very much in saving every last scrap of fuel econony, keeping tires inflated, brakes inspected (for dragging shoes or pads) and also, as in my case, doctoring the fuel a little and keeping the injectors, intake, EGR, PCV, exhaust and intake all moving properly. And if something breaks or wears out, it's upgraded when possible, rather than just replaced. :) It also helps to know a little about engineering and a few other disciplines to literally "tune" intake and exhaust to meet a range, or ideal "almost always operating within this range/piston firing frequency" rig-up that will maximize every drop of fuel that gets into the system. IMO, *shrug* High performance also means high efficiency. I'll post a little anectodal story that's just too good to put here in the off-topic thread in a minute. Tonight while coming back from a store across town - I had just a little too much fun. :evillol:

wolfox;
I've been using 2 ounces of acetone for every 10 gallons of gas for the last 6 months, and almost doubling my economy.

However I'm just wondering if you would care to share any of your other doctoring the fuel tips, to help us all out?

If you do thanks, and if you don't I can understand why

Thanks

Pick up a bottle of Castrol Super outboard oil. Use it at a rate of 2 Oz. to 10 gallons of gas. Premix it in a 1 to 5 gallon lawnmower tank and shake it up good before you dump it down the filler neck. People will look at you wierd, but screw 'em. You're doing good for the truck with a 500:1 ratio of lube in the gas. This does good for the fuel pump (As there is much lubricants that used to be in gasoline now missing these days) and it does a great job of keeping rings free, valve seats lubed, etc. This also helps reduce the "overhead" in horsepower needed to pop the valves off the seats, as they experience temperatures though they are hardened; that over time simply wears them out. A little lube in the gas acting as a "Top end lubricant" will go a long way to scavanging longevity, a few horses, and if done right, will not foul the plugs or adversly affect efficiency. However, be mindful of too much - stick to a 500:1 ratio and the acetone together and give that a shot. If you use or can only get Castrol Full Synthetic Super Outboard oil, dump the acetone into the car/truck's tank first to give it a chance to bond to the gasoline *first*. THen go to the back of the truck, pour out your measure of the oil into a gas can, fill and shake before dumping into the truck's tank. There is an organic ester in the synthetic formulation that percipitates out as a solid, ocre colored sludge if it's exposed to pure acetone. But once it touches gas, it dissolves. Safer to mix and pour them in one at a time instead of trying to mix it up in one batch for this reason. Party on! Oh, and if you are really brave, you can try "indexing" your plugs too. This is an old motorcycle racer's trick as old as the sport. On a bike it can get you a few extra horses, but it's a little more on a truck/car engine. Mark the side of the plug that has the open face of the electrode. You may have to try it a few times and possibly use washers to create a little back-spacing, but you want the open side facing the intake port. This sets up a pretty wicked flame-front in the combustion chamber that burns pretty even and forcefully. Trying this with Platinum or other precious metal plugs works well. I am going to experiement with a set of Denso U-Channel Iridium plugs when money comes back my way again.

A few final thoughts on fuel:

Try to shop a top teir gasoline retailer. These distributors have proven quality over all of their gasoline formulations. Once you have one you like, stick with them so you can get consistent results. Among these distributors are the likes of :

QuikTrip
Chevron
Conoco
Phillips
76
Shell
Entec Stations
MFA Oil Company
Kwik Trip/Kwik Star
The Somerset Refinery, Inc.
Chevron-Canada (B.C. only)

These fuel have consistent quality and have proven to contain detergency and fuel system cleaning agents in excess of minimum federal standards. These fuel will help keep the engine clean and reduce your dependancy on shock dose, fuel treatment products. And the biggest by-product is of course an engine that just runs great all the time once you get it cleaned up and lubed with the concoction I outlined above. Let us know what happens after you try mixing in the 2-Stroke oil. ;) I got my roomate trying it out on his Minivan and so far - he's tracked over 125 miles on less than a 1/4 tank of fuel in a utility vehicle that carries a 20 gallon tank. (17 gallons visible on the gage)

Thanks, wolfox;

I know that another trick that I can use is to gap the plugs as wide as they'll go without arcing to the side, or causing any missing.

It basicly does the same as indexing your plugs, giving a bigger flame.

Hold on guys.

Do NOT put 2 stroke outboard oil in a fuel injected vehicle. Never EVER EVER.......

This might have worked with standard CARB engines and mechanical pumps, but not on fuel injected engine with a cat convertor and an electric fuel pump. This will gum up the cat pretty quickly, foul the plugs and probably coat the O2 sensors with carbon which will cause them to take improper readings.

The whole point is to get the gas burning properly, not put oil in it which will hinder the burn when compared to standard fuel.

Bravada 97 needs to change his cap and rotor and he is probably due for new O2 sensors. They will wear out at about 100,000 miles.

I have a 97 with a 4.3 L. I have owned it for about 2 months. I bought it at 67k and it now has 70K miles on it. I noticed I was getting around 14.5-15 mpg with town driving and 19-19.5 mpg when on the highway. I did a tune up for good measure. New K&N filter, plugs, PCV valve, and fuel line filter just to be safe. I also started adding acetone to my gas at 3oz/10 gallons and my tire pressure is good as well.

Since doing all of this I have not seen any real increase in my mileage. Today it was still 19 on the highway. I don't drive hard and on the highway I travel from 65-68 mph @ 22-2300 RPM. I guess this mileage isn't bad but after seeing some of the others on here who are getting 17 in town and 23-24 on the highway I thought I may be able to get close to that as well. Does anyone have any other ideas to try?

BTW, isn't the Bravada AWD? That will affect the mileage a bit.

BTW, isn't the Bravada AWD? That will affect the mileage a bit.

It is AWD. The specs say it should get 21 mpg on the highway but that number was probably reached at 55 mph average speed.

You can expect your Bravada to get a little worse gas mileage than Blazers, due to your AWD. The specified fuel economy for yours is 16 city and 21 highway.

Have you replaced the cap and rotor?
Where does your temperature gauge read when the engine is warmed up?

On the gauge it is exactly half way between 100-210 degrees. I am not sure exactly what that is as the calibration on the gauge is odd. My gauge goes from 100-260 degrees.

On the gauge it is exactly half way between 100-210 degrees. I am not sure exactly what that is as the calibration on the gauge is odd. My gauge goes from 100-260 degrees.
That's what I figured that you would say. I would suspect a stuck thermostat, because it is the most common cause, however there have been a few people recently that have had the same problem after replacing the stat.. It should be one line left of 210. When mine was stuck the temp stayed right between 100 - 210. When the thermostats stick open a little, the engine doesn't reach operating temperature. When the engine doesn't reach operating temperature, the computer stays in open loop and doesn't go into closed loop. In open loop the computer uses default settings for the air/fuel mixture. These settings are usually a little rich and cause excess fuel consumption. While in closed loop, the computer monitors the O2 sensors and adjusts the air/fuel mixture accordingly, thus giving you better gas mileage.

Hold on guys.

Do NOT put 2 stroke outboard oil in a fuel injected vehicle. Never EVER EVER.......

This might have worked with standard CARB engines and mechanical pumps, but not on fuel injected engine with a cat convertor and an electric fuel pump. This will gum up the cat pretty quickly, foul the plugs and probably coat the O2 sensors with carbon which will cause them to take improper readings.

Mmmmmkay. But this is why I said to keep it to a 500:1 ratio. Any higher nets no real benefit and *could* lead to what you are saying if you use an organic based formulation. Newer formulations must meet or exceed NMMA TC-W3 which is also a low-to no smoke and ashless standard. Any old 2-stroke will not do. Dropping your plain old mix that you would use to say, run your Sthill chainsaw at a 50:1 ratio would screw things up like you describe for certain. My old carburetted V-8's got a really sensitive O2 sensor on it and I never got into any trouble sticking to this regimen on organic based 2-stroke mix held at a 500:1 ratio. I *doubt* O2 sensors have changed that much in all of the years they have been made.

The whole point is to get the gas burning properly, not put oil in it which will hinder the burn when compared to standard fuel.

2-stroke mix *lowers* octane, making it more prone to ignition. Adding a little "dope" of acetone mitigates this problem and keeps things clean too. Again, the reason why I stated the balance I stated above. What I have managed to find out is that this stuff really is no different than say, Lucas' product. It's merely refined oil, a few aromatic hydrocarbons...and a fancy label that cost more than the contents of the bottle to produce. If you follow my mix, you're duplicating it for a mere fraction of the cost. If you use the ashless Castrol Synthetic Super Outboard, it has the side benefit of dying your gasoline blue, just like aviation gas. :D

Bravada 97 needs to change his cap and rotor and he is probably due for new O2 sensors. They will wear out at about 100,000 miles.

This is true. The origional BOSCH OEM part that these trucks left the factory floor with are only good to 100k, maybe 150k miles if you are *lucky*. Keeping these sensors in good shape will keep acurate fuel trims and the ECM flying stright, maximizing fuel economy. Your truck's fuel economy will take a dump upwards of 25% loss if a sensor is slow or possibly not reaching operating temps fast enough when the heater inside of it quits with age. I didn't think about that BlazerLT. I always assume someone's already taken good care of the vehicle and evrything else is up to snuff. Teaches me to assume much. ;)

On the gauge it is exactly half way between 100-210 degrees. I am not sure exactly what that is as the calibration on the gauge is odd. My gauge goes from 100-260 degrees.

Yea, I think your thermostat is stuck open a bit. It should be between the 1/4 and 1/2 mark most of the time. A new thermostat should helpyour engine get up to temperature a bit better. You might be actually warm enough to be in closed loop, but not by much.

New thermostat and cap and rotor and you should be seeing some improvements.

Would the computer just retune the engine when you add acetone?

I recently did a complete brake job on my 1998 Bravada (66k). This did bump up the MPG's by 2.5. Found two stuck caliper pistons. Hopeful the rebulit units are better than the factory units. The overhead console also displays the wrong MPG's, do the math at the pump. My display read 13.8 MPG
currently averaging 16MPG (short trips).

I will check the thermostat and plan to change the cap and wires soon.

Doa full tuneup with the cap and rotor and wires, plugs, PCV valve, fuel filter anda new air filter.

Might want to clean the throttle body and the MAF too. Just some other stuff to include in routine maintenance.

Did anybody ask him what his gear ratios are? Just having a different gear ratio will account for a difference in gas mileage. 373 or 240 BIG BIG DIFFERENCE!

Did anybody ask him what his gear ratios are? Just having a different gear ratio will account for a difference in gas mileage. 373 or 240 BIG BIG DIFFERENCE!

220, 221 whatever it takes :evillol: