DLV555

iTrader: (1)

I've been seeing a lot of people saying their L03's are worth "25+ mpg" and similar numbers. Are we talking best ever or average? I have had my bird for a little over 3 months and the only time I saw better than 20 or 21 was when I moved from Houston to Atlanta and I averaged around 24. Since moving my fuel economy has dropped to about an 18 mpg average with, I would guess, 50/50 highway/city driving. In the last couple of weeks I have gotten a full tune up (accell plug wires, distributor cap, ignition module, MSD coil, Delco plugs) and added a dual snorkel air cleaner, though it is still missing the scoops and the hoses. I have also now changed my brand of gasoline...I don't know what's left to adjust, but I was definitely hoping for better economy out of a TBI 305 with 2.73 gears. I am still waiting to finish the tank of gas to do the math, but it is looking pretty similar to all my previous tanks. I had a Monte Carlo SS with the L69, 3.73 gears, and a 700-R4 and it was at least this good on gas. Where else should I be looking, or am I trying to squeeze blood from a stone?

vipershark11

iTrader: (6)

hell id give my nuts to get that kind of mileage my heavy foot doesnt help too much but i cant help myself even though these prices are getting rediculous i get way below what everyone else does prob even worse than an L98.

Green89IROC305

i got 19 city from my from my modded 91 rs tbi 2.73 gears. before i modded it i was getting 16-18 city/highway

this translated to 180 miles or so on 12.7 gallons of gas before mods and 24 to the same amount of gs after. roughly from memory or so

Damon

25 would probably be on the highway, not average (and in sharp tune). I suspect they are definitely capable of it. I've owned carbureted LG-4 motors that would push 25 with a 5-speed manual and 2.73s. My 94 Formula with 350 LT-1 would knock down 27 MPGs on the highway but that was with the MASSIVE 6th gear overdrive in the 6 speed manual trans.

robertfrank

iTrader: (27)

With my car I can pull an honest 300 CITY miles out of my car on a full tank.I ONLY use chevron 91 octane.then again I have 3.42 gears and my car weighs 3120 pounds with me in it.So to get around I don't have to put to much of my foot in it to get going.

Fast355

iTrader: (2)

I am getting an honest 500 miles (city) and 650 (highway) out of 30 gallons in my 350 TBI van. I say that a decent driven 305 TBI camaro should get very high teens to low 20s in town and mid to high 20s on the highway.

MJH91RS

Pure highway I get 25-26mpg. Pure city I get around 15-17 depends on how hard I'm layin in it.

I have the T-5 with 3.08 gears.

91ChevyRS

my ver best mileage streak was when I got around 19mpg in the city.

It steadily decreased after that and I am not so sure as to why. I think it may have been the fuel injector cleaner that I had put into the car before, that netted me so good of a gas mileage.

I get like 15-16 mpg in the city now, but I have also been driving my car like ***. I just filled up today, so I am gonna go back to my old driving habits and see if I can get that much again.

I used to average around 17.5-18mpg, I haven't been there in awhile.

If I don't get that same mileage I have been getting previously, I am gonna go ahead and try and find out why the hell its not doing it anymore...

83Chevy_Camaro

Stock 350 TBI from a 1988 Pickup in my 1988 camaro, and I was getting 23 mixed city and highway.. after lifting TB and Injectors, adding open air element, changing the timing to 3*advanced, 8.8mm plug wires.. i think that was it.. 2:73 rear gear and now i get 16-18mpg

r0nin89

I am an all stock LO3 with an open elment and I would say I get around 16-18 city driving like a complete moron. And when i say complete moron I mean flooring it til I'm doing the speedlimit Then letting off.

PS: We'll see what happens to my gas when i add my TB spacer and Injector spacer, I thought it would increase MPG but someone above said it decreased it...

okmaro

I get around 26mpg highway, but around the town I get alot less, I'm pretty lead-footed but when a LO3 can just cruise along they get pretty good mileage.

Treadin' 92

i get 21-22mpg city with the ac on and 24-25 without it
pretty much stock 92 rs, 2.73 a4, only mods are a k&n air filter and flowmaster exhaust
that and i changed the fuel pump, fuel filter, cleaned the injectors and throttle body

is it true that the injector spacer will hurt the fuel economy of the car?

brodyscamaro

I don't know about these #s


However my non locked up, carbed, big cammed 350 pulled 20 on the highway so i dunno, that was with 3.73s too...

Rod Behring

This will sound kind of funny, but switching to lower (higher numerically) rear end gears improved my overall gas mileage. My L03 T-5 with stock 3.08 gears averaged 19-20 MPG out of a tank of gas. This is with about 40% city and 60% highway driving. In all highway driving I got as much as 28 MPG. Now with 3.42 gears the best I get on the highway is 26MPG but my average is 23-24MPG. That is a 4 MPG improvement overall. I think the reason for this is that I'm able to use 5th gear more at lower speeds and I frequently start out in 2nd gear, especially in wet weather. I'm not sure if this would be the same with an automatic though.

DLV555

iTrader: (1)

Well, since I made this post I remembered that sometimes you have to fix the driver. I made serious changes to my driving habits. I've been super light on the throttle coming out of stops. And pulled my foot out of it in other situations too and my fuel economy has gone up a little bit. I am now starting to average 19-20 MPG even up to 21 MPG in my normal daily driving. And on a recent trip to North Carolina it was up to 26-27 MPG. I think the highway mileage was more due to the ignition and induction upgrades than the change in driving habits. This was much more of what I was expecting when I bought this car.

83Chevy_Camaro

How is your Catalytic convertor? I was getting around 18mpg, then i gutted the cat. and put in a 160*F thermostat, Tranny fluid cooler, Changed timing to 8-9* advanced and run nothing but super, and 108octane from the local dragstrip.. and doing 50-55 everyever possible, i Now get 25mpg, last calculated was 308miles on 12 gallons of gas.


Higher octane is something you need if you have any pinging in higher rpms, if you have no pinging or knocking higher octane wont help very much, Until you change you timing. If you can get your hand on a timing light, change the timing in little increments, such as 3* 6* 9* advanced, go for a few days on each setting, and remember anything after 3*advanced with swirl port heads will sometimes require higher octane, Premium mixed with the cheap stuff was plenty, i would get premuim one day get regular the next or whatever.. and never hand pinging, until i ran pure regular..

Try that, and check your cat, hit it with a wrench tell us the noise you hear, and we or i can tell you if its plugged or clear..

Nick

83Chevy_Camaro

Oh yea, If you cant or dont wanna screw with the timing.. Fill the car with gas, and reset your odometer, and for that whole tank of gas, dont let the engine see more than 3500rpms and then calculate you mpg..

Jason E

My RS gets 16-17 in nothing but stop and go, and 25-26 on highway trips. Considering the original EPA ratings on the window sticker were 17/26, and the car is 15 years old with almost 110k miles, I'm pretty damn happy with that It gets better mileage than my old, mint condition A4/2.8/3.42 geared '89 RS!!!

JustinSane

well as promised to day i took a 8 hour trip and i took the camaro, The car is a bone stock 91 rs 305 with 2 degrees timing and a truck air cleaner base plumbed for cold air and a gutted cat. Its a auto with 2.73 gears. The trip was in 100% humidity with alot of rain. The route was threw PA across 80 which if you dont know isnt very flat. So i stopped and topped of the tank and set the cruise to 75 MPH which is 1700 rpms about 2 hours later i stopped and topped off again and did the math. It came out to 30 MPG and i know i could have done better hadnt it been for the hills and bad weather. plus my tires are bald and that little extra height of new tires coulda helped squeeze out a bit more. This car does about as good as my 92 saturn and only 5 mpg less then my 87 escort GT.

Black85sport

Just out of curiousity, how do you know that you had the same amount of fuel in the tank the second time you "topped off" your car? By "topping it off," do you mean filling it until the nozzle clicks, or pumping gas until you believe it is topped off?

The only way to accurately check fuel mileage is to fill the car until the nozzle clicks, drive it, then fill it again until the nozzle clicks, then do your math. I'm not saying this is a 100% true, dead on way to calculate fuel mileage, it is alot more reliable than "guessing" how much fuel is in the tank when it has been "topped off"

There is no way you got 30mpg, especially with an auto.

JustinSane

Double Posted by mistake.

JustinSane

I know how to check MPG And no matter if you believe me or not I got 30 mpg you only look silly trying to tell me that i didnt get what i got. And I am sure i could have got better if the cruise hadnt had to keep kicking in for all the hills. and for your information a 700R4 has a lock up converter and with OD and 2.73 gears you would be hard pressed to find a 5 speed that can do better then 1700 RPM at 75 MPH in a 91 3rd gen
but incase you want to check here is our data
miles at top off 37894
miles at second top off 38043 toped of in the exact same way as first top off
gallons took to top off 4.97 now im no math teacher but that comes out to 29.9798
with good tires and less flat highway this car could get 31 32 MPG no doubt. but what do i know i only spent 13 years feeding my family as a ASE Tech.
I have no idea what MPG the car got bone stock since the last owner had the cat gutted and i changed the aircleaner as soon as i saw that pathetic snorkle.

sprojam

there is a company called ethos check it out i have a hotroded 86 z and like the other guy have a heavy foot but seen a 10% gain on the First tank and 20% on second sence then has been bouncein between there you can find them at ethosfr.com worked for me anyways

JustinSane

neat stuff, but i cant wait untill i get headers and exhaust frm what i read here my MPG will get a little better then. that should put me in low 30's then when i put slightly lower gears in it that should put me right back to where i am and as long as im pulling 30 on highway im pleased as can be. I even put my escort in the paper this week lol i dont need it with this car getting almost as good of MPG.

DubyaSsixTA

I drive 50/50 highway roughly and usualy get around 22-23. This last tank I used the cruise and stayed out of traffic as much (I work weird hours) with more cruising and got 25.9. The one trip I took was bringing it home and it got 25.4, which could have been better had we not had to pull over for some unexpected severe weather.

JustinSane

very nice. i recently installed the cat back set up from edelbrock RPM series and that with my larger aircleaner snorkle and running 2+ degrees timing took me from high 16,s in the 1/4 to a best of 15.4. still getting the same economy on highway 29-31. i never bothered testing around town but its great i can go forever on a tank of fuel in this baby. Soon i will be considering a gear swap and im thinking around 3.55's i dont want to get any worse then 25 highway but i do race on weekends and these 2.73's just dont cut it.

kdrolt

In my 4100 lb 93 Caprice (LO3 TBI, presently bone stock) I routinely avg 22 mpg mixed driving; the best I have observed is 26.6 mpg that was 80% highway. That was on what were probably the original plugs/wires (old guy car from Florida with only 46k miles), so I expect that a full tune up and tire inflation check would get me 27+ highway, and 23+ city.

A 3rdgen Fcar that weighs 600+ lbs less than my Caprice and it has a smaller frontal area (for less drag), so a 3rdgen Fcar should beat my figures by at least 2-3 mpg so long as the driver doesn't have a heavy foot, and the engine is in good shape. And FWIW my old car was a 94 LT1 copcar Caprice, and the best it ever did was 22.7 highway; it avgd 16-17 city and 20-21 highway. So I'm not surprised by how thrifty the LO3 is.

ezysk

My plain jane 86 Carbureted Firebird runs 20-21 MPG Combo driving.
I have measured it carefully using the trip for about 3 months.

The car is stock, except headers and 3" Flowmasters with Cat delete.
Still have the 20 year old, in big need of a rebuild Carb and oxy sensor disconnected.

What I am really surprised at, is not that all our cars get this gas mileage.
It is that 20 years later, the average current car does not do a hell of a lot better.
And before someone says it, I am saying the average car, not the high efficiency econo cars. There are always exceptions to the rule.
And before someone says, well my buddies Mini Van gets 40MPG, check it out on the dealers site, I bet it doesn't.
Note: The first And for exceptions to the rules.

Fast355

iTrader: (2)

My stock 175 HP LE9 305 carbed Chevy Van with a 700r4 and 3.08 gears would pull down 15 city/20 highway(lookup the EPA ratings for like a 1985 (same van, same engine, same carb, same trans, same rear) if you don't believe me) and averaged about 17 mpg overall. I converted the still stock 305 to TBI fuel injection. With the stock 305 caprice prom and stock 350 61 lb/hr injectors that were in the TBI, it would pull down 22-23 MPG highway and I was averaging about 18-19 between fill-ups. I too believe in the frugalness of the L03.

MonteCarSlow

Stock 89 L03 w/A4 in a 4000+lb Jaguar with 2.88 gears. Always averaged 20-21 mpg (mixed - mostly highway), and easily 26-27 purely highway (55mph). The only thing non-factory was the rams horn exhaust manifolds and true dual exhaust with cats and mufflers.

beatercoprice

92 caprice cop car, L05 350, 700r4, 3.42 posi, slight exuast manifold leak. 20 mpg in mixed driving.

gray89vert

iTrader: (3)

just a guess i get around 13. check the sig for mods...i just can't keep my foot off the floor i guess

91black5spd

Here is what I get, I have Stock L03 w/ T5 Tranny, fresh tune up, catback exhaust and K&N filter:
18-19 City
26-28 Pure Highway ~70mph

89stroker

if i keep mine < or = to 75 i can get over 18 mpg with my truck.

UnderCover89TBI

iTrader: (25)

my 305 got great mileage

Cadillac

Best Ever: SF to LA, 26 MPG. Avg speed 85 mpg. Tall 2.73 gears and highway mode.

In and around the Bay Area, 15 mpg or about 225 miles per tank (15 gallons).

101 sucks.

snflupigus

bill used to get 300 miles out of tank in the car I now have... I get about 210.

My truck gets 13 combined. overhead says 2 when i floor it.

Rossi

Yep.

copperhead110

When my 88 lo3 was new, it would get high 20's. 27/28 mpg
Over the years it crept down to about 25/26 mpg.

A tune up at the dealship made the mileage jump back up to 28 mpg.
I don't recall what the did. One thing they replaced was the EGR.
they replaced my autozone one with a GM one. This was on highway trips from Dallas to Kansas City and back.

I also had a drop in mileage when I bought cheaper tires. the milaged dropped 2 mpg. Back then the car was about 3 years old. After switching back to eagle GTs the mileage went back up. This was 90% highway.

now its only getting 21 on the highway.

Personal record was 30 mpg.