Fuel Question

[Clod_King]

Okay, so i am going to be taking in my suburban for the final stages of my E-test, and I want fresh fuel in there. The truck has like a quarter tank in it, and I bought a bottle of Octane booster, but will that even revive it?? Or should I drain it, and put new fuel in it??

Also, would dumping the octane booster in a fresh tank of gas be a bad idea?? I've buying high octane fuel is bad for engines that do not need it??

And will a higher octane reated fuel help the truck to test better, or will the TBI compensate for the higher octane level, and it will do poop for me.

I already bought the bottle, so i don't want to waste it.

 

[dyeager535]

Higher octane will only hurt you...higher octane is more resistant to burn, the opposite of what you want for an e-test. (which is why alcohol helps)

Octane boost in a can does minimal good, ESPECIALLY on a full tank. IIRC it works out to something like 1 octane "point" is the max it will raise an entire tank of gas. Hardly worth it.

Run what the engine was designed for, 87 octane.

 

[Clod_King]

what about on a quarter tank? I don't have a jerry can or anything, so I can bring fuel to my truck, I have to bring my truck to fuel. hahaha.

Is it a bad idea to just run the fuel dry??

 

[dyeager535]

I don't like running it out of gas. You run the possibility of pulling all the crud at the bottom of the tank to the sock filter, not to mention that is how the fuel pump cools itself.

If it's bad gas, I'd pump it out. Easiest I've found is remove the fuel filter and run the pump with the wire hanging off of the fuel pump relay. This of course, if your gauge is accurate.

How bad is the gas? Is it really a problem, or you are trying to get the best possible? If it's ok to drive, and you have time, go fill it up, burn that tank up, and fill again.

 

[4by4bygod]

Okay, so i am going to be taking in my suburban for the final stages of my E-test, and I want fresh fuel in there. The truck has like a quarter tank in it, and I bought a bottle of Octane booster, but will that even revive it?? Or should I drain it, and put new fuel in it??

Also, would dumping the octane booster in a fresh tank of gas be a bad idea?? I've buying high octane fuel is bad for engines that do not need it??

And will a higher octane reated fuel help the truck to test better, or will the TBI compensate for the higher octane level, and it will do poop for me.

I already bought the bottle, so i don't want to waste it.

Octane boosters like 0 -60, outlaw, etc are just kerosene mixed with metallic additives that really only serve to build up more carbon upon combustion..not what you want for an emissions test.

For emissions tests, having clean oil in there ( and new plugs/wires/cap/rotor) is more important than what fuel you are using.

As to your other questions, remember, octane level describes the fuels ability to reisist detonation.. octane is not a value that denotes a power level ( the power output of a given fuel is determined by the btu, or "thermal energy" contained in that fuel, and that is affected by the composition of the fuel itself and how it's refined)

As for a truck being "designed to run" on 87, it's more accurate to say that modern vehicles are "designed to compensate" for 87 octane via the knock sensor pulling out ( retarding) timing when it senses detonation..this leads to reduced power and mileage..

A higher octane fuel might produce the opposite effect ( more power and mileage), but only if it has a high motor octane number in the RM/2 equation.. not all do. A high research octane number in the equation can give a higher total octane number, while performing no better than 87.. that's why you can use 91 pump gas and still hammer like a woodpecker.

your best bet is to find a brand of fuel and an octane level the truck runs best at and stick with it, and recognize that advertised octane levels are just that, and the performance will vary depending on atmosphere, engine, and fuel composition..


Tom

 

[dyeager535]

As for a truck being "designed to run" on 87, it's more accurate to say that modern vehicles are "designed to compensate" for 87 octane via the knock sensor pulling out ( retarding) timing when it senses detonation..this leads to reduced power and mileage..

That's not really true at all. GM sets the timing and fueling maps based on the type of fuel the engine is designed for. If the ECM is retarding timing based on detonation, something is wrong and outside of the parameters of correct engine operation. Timing is "static" based on the PROM settings, only when the engine is not running correctly is timing no longer based on the timing maps. It cannot "compensate" for higher octane, only attempt to prevent engine damage if it's detonating.

Fuel is most certainly one of the factors in GM determing the timing maps, along with the entire engine setup.

Putting 91 in a truck designed for 87 will accomplish nothing. Sure, you can bump the timing, but that doesn't mean you are actually getting more power out of it. Possible? Yes. Always? No.

Putting 87 in a vehicle designed for 91 will certainly reduce power and mileage. The engine will detonate (higher compression, fuel not resistant to detonation equals combustion before intended/best time) and if computerized, will theoretically retard timing.

 

[4by4bygod]

That's not really true at all. GM sets the timing and fueling maps based on the type of fuel the engine is designed for. If the ECM is retarding timing based on detonation, something is wrong and outside of the parameters of correct engine operation. Timing is "static" based on the PROM settings, only when the engine is not running correctly is timing no longer based on the timing maps. It cannot "compensate" for higher octane, only attempt to prevent engine damage if it's detonating.

Fuel is most certainly one of the factors in GM determing the timing maps, along with the entire engine setup.

Putting 91 in a truck designed for 87 will accomplish nothing. Sure, you can bump the timing, but that doesn't mean you are actually getting more power out of it. Possible? Yes. Always? No.

Putting 87 in a vehicle designed for 91 will certainly reduce power and mileage. The engine will detonate (higher compression, fuel not resistant to detonation equals combustion before intended/best time) and if computerized, will theoretically retard timing.

Hi Dorian, Thanks for weighing in..

I don't know that we really disagree ... My point is that not all 87 octane fuels are created equally..I've seen one too many fuel analysis printouts come back where the measured octane ( or cetane) values differ wildly from what is advertised on the pump.

today's engine management systems will compensate so that if you get a fuel that acts more like an 85 octane (thanks to a higher research octane ), the computer will retard the timing (within given parameters, as you pointed out)so knocking is prevented, thus leading to the conclusion that advertised 87 octane is the optimum fuel, when it may not be the case.

since the engine management systems are adpative, it makes sense to at least play with various octane levels to see what the vehicle likes.. of course, realizing that the computer parameters will let you go only so far.

And yes, if someone gets to the point where a higher octane fuel isn't netting a performance benfit, and they are still buying the more expensive fuel, then they are wasting money for no reason.

Tom

 

[4xcrazy]

I don't like running it out of gas. You run the possibility of pulling all the crud at the bottom of the tank to the sock filter, not to mention that is how the fuel pump cools itself.

.

pulled many fuel pumps out lately? the fuel pickup is at the bottom of the tank ALL the time anyways, doesn't ride with the float.....

 

[Clod_King]

My pump, and sender are brand new, and are waiting to go into the tank today. I geuss I will just pump it all out, and buy a jerry can, then dump gas into her.

I am not worried about sucking up crud, because I ran my last truck until the needle sat at the bottom of the gauge then i filled up. I like to keep my fuel all the same age.

The stuff in the truck right now is a year old (did I already say this??) but it runs.... when the gas tank is up, and has fuel lines, hahaha.

What is a good octane level to start at. you guys scared me now with all of that information. ignorance is bliss, you know?

 

[dyeager535]

Nop, but with an empty tank of gas, you are certainly drawing all the crud that has settled AWAY from the pickup towards it. The bottom of the tank is a huge area compared to the amount of suction the pump has, and since the tank bottom is essentially flat, anything that falls into the tank (rust, stuff from fuel) can stay right where it is without heading straight to the sock filter.

Not only that, any water that is in there you are more likely to pull through the sock filter (which is designed to prevent that) if the tank is run empty. Then it's in the rest of your fuel system.

I've pulled plenty of tanks, and the grit that was in the tank was evenly spread about the bottom.

 

[dyeager535]

Stock truck, run it on 87. You can do as suggested and play around with the fuel quality, but I've done back to back testing as scientific as possible, never noticed any performance or mileage gains going higher.

Fuel quality is probably fairly spotty if you get real precise in analyzing it anyway, but I've NEVER had a bad tank of gas. Knock on wood. I know it happens, just hasn't happened to me yet.

 

[Clod_King]

I used to buy that 91 stuff for my stock '79 pick up. I thought I noticed a difference, but I think I was just huffing to many fumes because of my leaky carb. hahaha


I'll stick with 87, and fiddle around a litle bit. So do different gas stations have different types of fuel?? like an 87 octane at Sunoco, would be different then the 87 at Petro??

thanks again guys, this information is priceless.

 

[4xcrazy]

I've pulled plenty of tanks, and the grit that was in the tank was evenly spread about the bottom.

because the sock was doing it's job, and keeping it OUT of the rest of the fuel system...... you don't think stuff at the bottom of the tank doesn't move around, with even HALF tank level? fuel sloshes around, moving everything in there..

this is old timer thinking here with the "picking up crud when you run empty"

maybe the old style setups, and i mean OLD.
I hear this about Diesel trucks as well,,,,again, the pickup is at the bottom all the time, and i know for a fact that fuel sloshes around keeping ANY debris in movement until everything stops....like when removing a fuel tank....come on now



More for what the question that needs answered, how old exactly IS the fuel currently in the tank??? It CAN sit for some time, may not be the best stuff, but if you simply run MORE clean fuel in it, it's NOT going to hurt anything, or cause a major issue with emissions.......

 

[4by4bygod]

I'll stick with 87, and fiddle around a litle bit. So do different gas stations have different types of fuel?? like an 87 octane at Sunoco, would be different then the 87 at Petro??

thanks again guys, this information is priceless.

Well, the quality can vary between sunoco and petro ( petrocanada?) because each refiner may get crude from differing sources, and subject it to many different procedures through the refining process, adding their own chemicals as they go.

For example, The USEPA says the refiners here have to drastically reduce the amount of sulfur in gasoline, just like diesel.. the "desulfurization" process ( in addition to reducing sulfur) diminishes a fuels ability to resist detonation ( IE: results in a lower octane value), so it has to be additized by the refiner to boost it back up..how they do that can vary.. for example:

here in the states, we have a mandated ban on the oxygenate MTBE,(which was the lead substitute used to boost octane) so we have a 10% ethanol blend as a replacement.. ethanol claims a high octane rating, sure, but it has lower thermal energy, so the net result is a bit less mileage and power.. there's always a tradeoff. Plus, ethanol comes from different sources, and there isn't a renewable fuels quality standard, so each drum of it has differing qualities producing different results.

so, one company's 87 can be different from another, just based on the amount and type of oxygenate that is blended..factor in your driving habits, your vehicles characteristics, plus the different btu content, detergents, aromatics, vapor pressures, and everything else mandated by the clean air nazi's, you can see how a fuels performance from one company to the next can be different.

Gasoline is put together like a recipie for grandmas chicken soup.. you have the recipie, but each batch has some variations in it, depending on the cook, and the individual ingredients..

Tom

 

[4by4bygod]

Dorian

With the tanks you've pulled.. have you ever noticed the nylon sock to "eaten away"?

I have heard that octane boosters containing MMT ( and other metallics )like 0 -60, outlaw, etc. like to eat that sock.. I've never seen it myself , only read about it. Interested to know what you've seen.

Tom

 

[dyeager535]

I've seen the "socks" worn out, but it seems to me to be more because of abrasion against the bottom of the tank.

The sock is actually supposed to keep out dirt AND water.

Fuel may slosh, but the crud is heavier and tends to stay in place. Put some sand in a bowl and add a bit of water. Slosh it. Does the sand tend to stay in place or move in concert with the water? Same principle. Probably even less likely to be a problem on a fuel injected rig since the pickup is in a sump that does not have "direct" access to the fuel in the tank.

Pump cooling alone is enough for me to not want to run my tank dry.

 

[Clod_King]

Yeah I didn't know that the pump cooled itself by the fuel. Hell I didn't even think about that before! hahaha.

Yeah I am talking about Petro Canada.

Hey 4by4bygod,

How do have so much knowledge on gasoline anyways?? Did you research it?? Or does your work have to deal with it??

Oh and by the way, I pumped my tank semi dry (maybe a pop cans worth left in the corner), and then dumped the fuel down the filler tube of my dads, and brothers cars, hahaha.

And I ponied up the dough for a jerry can too. Best 15 bucks I have spent in about 12 hours. hahaha. I bought my fuel sender unit yesterday, and that is obviously a better buy.....


And a question that you guys may, or may not know the answer too. The steel braided hose linking the sender to the hard line has an o-ring on the sender end. It isn't the normal flare. I want to know if the braided lines coming from the engine have the same kind of "unions". Thanks a gazillion guys.

 

[dyeager535]

Same connectors, called "Saginaw". Real pain since they aren't a "standard" fitting. Work good, but when you have to adapt to them, yuck.

 

[Clod_King]

d@mn!t

I hate those things. Gotta go back to the hydraulics place then.

Thanks man. Now it won't be a rude suprise when I take the line off.

 

[4by4bygod]

Hey 4by4bygod,

How do have so much knowledge on gasoline anyways?? Did you research it?? Or does your work have to deal with it??

Yes to both.. I work for American Clean Energy Systems, ( you can check my vendor thread in my sig to learn more about them), and all we do is help our fleet customers overcome the EPA - mandated changes to gasoline, diesel fuel, and motor oil. I have to keep up on this stuff, so I can be a good resource for everyone.. I am lucky that I have good teachers, and I have also gotten a lot of help here, which is why I sprang for a vendor membership..I wanted to support the site, and also make folks aware of issues and solutions they might otherwise never hear about..

Tom