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Gas milage question.


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5 replies to this topic

#1 Dominic g

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  • Year: 1993
  • Make: Pontiac Firebird
  • Model: Trans am
  • Engine: Lt1 v8
  • Transmission: Auto 4 speed

Posted A week ago

Hey guys, i was wondering how many miles the 1993 trans am will go to empty. I want to see if my gas gauge is correct. I would like a rough estimate on how far people have gone until empty. I dont trust my gas gauge on my car since i dont know how much is left in the tank from full to 1/4 on the gauge. Does empty mean empty on the gauge? Some cars have gas left in the tank just enough to get you to a pump to refill. Id rather be safe than sorry so id like to know how many miles i can go approximately from full to empty. Thanks guys :)

#2 Injuneer

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Posted A week ago

The gas gauge in the 4th Gens is notoriously inaccurate, and the there is nothing you can do about it.  If you are down to 1/4 tank, you may have as little as 1 or 2 gallons left.

 

Shoebox has a good description of the problem:

 

http://shbox.com/1/4...html#fuel_gauge


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FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
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#3 Dominic g

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  • Year: 1993
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  • Model: Trans am
  • Engine: Lt1 v8
  • Transmission: Auto 4 speed

Posted A week ago

Well then. Good to know. I had 1.1 gallons left at the 1/4 mark on my gague. Very in accurate indeed.

#4 ZumpTA

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Posted A week ago

Everybody's fuel economy is different.  For example, even if we drove the exact same way with identical cars, I live in Florida where the terrain is flat, so my engine isn't working like yours. 

 

Injuneer pointed out the fuel gauge issue, and that is important to know for sure.  ...but economy?  That is for you to find out. 

 

Fill  your tank, drive 100 miles, fill your tank again to the same level.  Divide your miles driven (100) by the number of gallons you drove.   If you put in 5.8 gallons in and went 100 miles, that is 100 divided by 5.8 which gives you 17.24MPG.  Now, multiply 17x14 and you get 238 miles.  That is how far you can expect to stretch a tank of fuel.  YES, you could multiply 17.24 by the actual tank size and get a higher number, but, with changing environmental factors, changing moods, and maybe needing "just one more gallon to get me there", it's better to underestimate by that .25MPG and forget about that last gallon or so of the tank. E means Empty in these cars if the fuel level sending unit is still accurate.

 

The biggie in my book was Ethanol blended fuel (E10).  I was pulling between 18 and 24MPG city in my T/A.  Eventually, my pump became E10, and my fuel economy fell dramatically.  I chased every issue of "lost fuel economy" and found nothing wrong with my engine or it's systems.  I gave up and accepted 16MPG *at best*, after all that is all I was expecting when I got it.  A couple years later, the under hood fuel lines started developing pin-holes and shooting fuel across my engine compartment or onto my exhaust manifolds.  That is when I suspected Ethanol might be an issue.  Learned my car is old enough that Ethanol isn't the best thing for it and should be avoided.  Found an Ethanol free (E0) pump, filled my tank, drove it out, filled again, and on the next fill-up checked my fuel economy again.  19.3MPG.  I have reached as high as 21 city since, but I'm a "spirited" driver and 18-19MPG is where I most often found myself before the Ethanol fiasco. 

 

Now, I not only have better fuel economy on E0 fuel, my fuel lines haven't sprung a leak since going back to it 6 years ago. I am pretty sure I can feel the difference between the two as well, but "seat of the pants" is often wrong and certainly isn't scientific.  All I do know for a fact is in my T/A, a 10% blend of ethanol with the gasoline means a 30% (+/-)  reduction in fuel economy.   The difference in price is worth it to me not only in recovered economy, but also in the fact my fuel system is no longer being eaten away, and more importantly, when my car sits for a month or three, I don't have to worry about ethanol collecting water or separating from the fuel and occupying the bottom of the tank then getting sucked up into the engine on first restart.  If 10% ethanol is bad, imagine 100%.   Ethanol isn't good at sitting stabilized or not.  The stuff is EVIL.  There is a YouTube channel called Project Farm, he's done a couple videos on Ethanol.  In one of them, he tested ethanol-v-regular after they had been sitting for a couple months or something.  Even "stabilized", the ethanol fuel would not combust in his "see thru head" lawnmower, the regular fuel was a "hard start", but the engine did start, and it ran just fine.

 

But, back on point. we have different vehicles.  Although they were mostly the same when they left the factory (mine's a 6-spd) they have had vastly different lives and upkeep. Mechanical condition impacts fuel and oil economy. As such, me saying I know for a fact my friends T/A gets 18MPG city doesn't translate to you, because again, "Florida".  Also, I can't give you a mileage estimate either.  I think my 1993 is 15 gallons (or maybe just shy of 15), some were 15.5, some ended up with nearly 17 gallon tanks.  Capacity was increased over the 9 year production run, and the LS engine was introduced in 1998.

 

So, fill it up, drive a little, fill it up, and check *your* economy.  Use that number to estimate how far a tank of fuel will carry you.   

 

...and if you haven't already done so, find an E0 pump and stick with it.  Around here, every other WAWA and Shell have E0 as do numerous small "mom and pop" stations.  Major stations (although not every one) will have at least 1 E0 pump because of Boats and small gas engines.  It might be easier for me as there are a lot of boats and landscaping companies in this state, but boats and lawnmowers are everywhere, so you should be able to locate at least 1 within 10 miles of your residence.


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#5 Dominic g

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  • Year: 1993
  • Make: Pontiac Firebird
  • Model: Trans am
  • Engine: Lt1 v8
  • Transmission: Auto 4 speed

Posted A week ago

the Ethanol thing you mentioned are interesting. Thank you for the information. I did a little math and found out an approximate amount of miles i can go both on the freeway and in the city. Thanks guys for the help.

Edited by Dominic g, A week ago.


#6 Injuneer

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  • Engine: 381ci LT1 stroker
  • Transmission: TH400 + GV O/D

Posted A week ago

I would strongly recommend you fill it as soon as the gauge drops below 1/2.  On my 94, when the needle was on 1/2, I had used 10 gallons and only had 5.5 gallons left.  Running out of fuel seems to be the cause of many fuel pump failures, based on feedback from people on sites like this, over the past 20+ years I've been following these cars.

 

To clarify, GM used the same 15.5-gallon steel fuel tank from 1982-1998.  In 1999, second year of the LS1, GM switched to a 16.8-gallon plastic tank.

 

To further clarify:

- E10 has been in use since 1979.

- the 1993 Owner's Manual indicates "Properly-blended fuel that is no more the 10% ethanol is fine for your vehicle"

- the parts in the 1993 (and newer) LT1 were selected based on E10 - example, the nylon fuel lines (which everyone calls "cheap plastic" and criticizes).  Nylon is highly resistant to ethanol

 

The problem comes when, as described above, the vehicle is allowed to sit for extended periods of time without a fuel stabilizer.  In regular daily use you should not have problems with E10.  These cars are now 25+ years old.  In the course of helping people on sites like this for 20+ years, specifically dealing with the 1993-1997 LT1 cars, I have not seen an abundance of people having issues with E10 fuel.  The problems definitely crop up when the vehicle is allowed to sit for 6 months or more.

 

E10 availability varies significantly by state.  Go to this site to determine the location of E10 fuel availability in your area:

 

https://www.pure-gas.org

 

In FL they show over 1,000 locations.  In WA there are 300+ locations.  But here in NJ we only have 12.  5 of those are airports, 2 of them are marinas, and 3 of them are VP Fuel distributors.  VP Fuels are only sold in containers, ranging from 5 - 54 gallons.  I used their highly leaded C16 ( (R+M)/2 = 118 octane) in my Formula for racing, and it's currently $20/gallon.

 

A 30% loss of fuel economy with E10 vs. straight gasoline is unusual.  EPA indicates the loss is 3%.  Magazines like Road and Track report similar numbers, but do indicate some readers report losses of 6-10%.  Organizations that promote the use of ethanol, like the American Coalition For Ethanol offer test data indicating 1.5% loss, but of course that is probably a bunch of corn farmers who make money selling corn to make ethanol.

 

I would agree that E10 fuel in small engines - snow blowers, weed wackers, pressure washers, etc. that do not get used regularly - causes major problems.  Sunoco, VP Fuels and others sell non-ethanol fuels specifically blended for small engines in 5-gallon pails for $12-14/gallon.

 

 






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