what do all of you guys get with your tbi's? i have done a full tune up including plugs, wires, cap, coil, fuel filter, and oxygen sensor. i just did the complete seafoam treatment today and wow it runs smooth now. i squeezed out 16.5 mpg and still had a little bit of fun.

 

what is this seafoam i hear everyone talking about? anyways i have never checked my millage, but all in all i would say its pretty good. i would say about 24 highway and about 18 city. once i get my car up to speed and set the cruise i would say its very efficient. i get much better millage than most people would give it credit for. if you keep these cars stock/mildly modified and not go crazy they are excellent daily drivers. excellent handling, enough power for street use, dependable, and decent fuel millage. a stock/mild 305 or 350 in a third gen is still a practical daily use car. if you go with a 383 stroker or something more exotic then the car is no longer practical for real world daily driving.

 

I HIGHLY disagree with this statement. A properly built 383 with a PRACTICAL head/cam/induction setup is a VERY streetable setup for real world driving.

My current 350 is making 369 RWHP @ 5,800 rpm/ 386 RWTQ @ 3,800 rpm and still gets 18 mpg in daily driving, pulling 5,500 lbs of aerodynamic brick.

 

In fact, a properly built engine with efficency in mind will do better than these stock, 1980's designed engines. You could easily take advantage of a 383's massive torque and nail some pretty impressive numbers if thats your goal.

My near-stock LO3 got about 20mpg combined. If it's straight highway, I'd get about 25mpg or so.

 

Jeez...my car sux...I think I'm getting about 8-10mpg right now. It runs great though. I'm sure it could use a tune-up, but damn I don't think that's going to get an extra 10mpg. Of course I'm not running an LO3 any longer.

 

i also have headers and free flowing exhaust. so that helped me out. i dont get how you can get 18 mpg or better! lol. im thinkin about doing the ultimate tbi mods. maybe that will help a little.

 

I guess I should add that I never "had any fun" with that car. It was just a here-to-there mule. I was always sooo dissapointed when I floored it that I just stopped flooring it.

I doubt the ultimate tbi mods will gain you any milage at all, cause thats not what they are for. They are used to increase airflow through the throttle-body...but unless you've swapped heads or at least the cam, your not gonna need it.

 

combined city and highway driving i get 19-22 and have a little fun every once in awhile . usually once every other time i drive it. overdrive is your friend.

 

yea i get 27 highway and 19 city, and still have some fun, and this is with a 350 tbi

 

Now that I have moved a little further from work the daily commute has more highway time. The 'bird is getting low to mid 20's regularly now when before it was getting upper teens. The wife is driving it since I bought my SS, and I KNOW I get better mpg than her in that car. Our commute is the same.

 

When my car was near stock (cat-back and open element only) I would get no less than 31mpg on the highway. Medium optioned, T5 and stock 3.08 gears with the tiny 15x7 wheels.

 

I get about 28 MPG on the highway with my stock 305 TBI, 5 speed manual and 3.08 rear end.

 

Wow... my RS sucks pretty bad... I only get 9 or 10 city... L03 Auto.

It jumped up from 6-8 when i did the tune-up, but i have only gotten better than 10 about a handful of times in the 7 years ive owned my car.

What's worse, is i dont "have fun" when i drive. Maybe its the California traffic? Or is my car just about to die? It has 200K on it...

Doesnt that just seem a little out of the normal?

-Tim-

 

150K+ L05 in a 92 caprice that weighs somewhere over 2 tons. 3.42 gears and a 700r4. I usually average around 22mpg mostly highway. I have pulled a best of 24 and change.

 

171,000+ miles and I get around 20 mpg combined.

 

i thought 16.5 was pretty good for what i have done to my car. why is almsot everyone elses so much better?

 

mines gets about 310 miles from F to E and i have a c91 caprice 350 motor w/ free flow exhaust and cam i guess its accpetable

 

I also have a Caprice sedan (93 model, 70k miles) and right now the LO3 engine (identical to a 3rdgen LO3) is 100% factory. On the prior fill-up I went 529 miles and avg'd 27.2 mpg. Today's fill-up was 532 miles and 27.9 mpg. The driving is mostly 40-50 mph over 60 miles per day during the week. And yes, I fill the tank each time until the pump does an autostop. So anyone here that claims 28+ mpg in a 3rdgen Fcar will get no doubts from me, because they're some 500+ lb lighter and has a smaller frontal area. So driven conservatively on the highway, over 30 mpg would not surprise me.

Things to remember: the engine in my car has relatively low miles and it's in very good shape. The trans is obviously a 4L60 and the rear end is (gasp) 2.56. I have never taken the car to the track.... but there is little point given the engine and rear end. It should run low 17s. I use 100% synthetic oil, and I change it (plus filter) typically every 4000 to 6000 miles. The EGR is functioning properly so lean cruise works.

I'm being rather careful about tracking the mileage so that I can note any changes (hopefully positive) after I alter the air cleaner to one of these, alter the exhaust (probably to Bcar 94-96 N10 full duals, and a few other things.

To compare, the best I ever got in my 93 Buick RM wagon was 21.6 mpg, which was mostly highway on a 3.23 rear end and a civilian pure factory TBI LO5. The best I ever got in my old 94 Caprice LT1 copcar was 22.7, again on mostly highway driving. FWIW.

 

I get average 21mpg. It did drop to 15 but my EGR went out, and came back up since. I left the beach 214 miles later pulled down driveway, and with half a tank left to go. I figured 15 gal divided by two 7.5, so around 28mpg. Did I figure that right? I not complaining though!!!

 

I average about 25 with 2.73 gears(iirc) with 16's and at 80 miles an hour My math may be a lil fuzzy but I can go roughly 300 miles or so I a tank of regular. Its a 305 tbi turning a total of 273,000 miles. On my rebuild maybe maybe 130,000. Thats freeway. My town driving I can kill a quarter of a tank in like 1 hour or so.

 

The old L03 I had seemed great on gas but honestly gas was 1.00 a gallon when that was in the car! I do have a direct comparison from my TPI 350 and my 4.3 TBI S10 (2980 curb weight, tail gate up, dual exhaust, manual steering and Efan). We took both of these vehicles to IRP from my house, it's a 97 mile trip there and 97 miles back. Not even counting the gas used on the runs at the track, and the offshoots we took to get gas the truck broke 25mpg and the Camaro did a shocking 20.5 with a 3 speed and 3.27's! The truck can do pretty good on milleage especially drafting but the Camaro amazed me I never thought it would do milleage like that running at 2500 to 3000rpm for over an hour. One thing I do do that's contraversial but I recommend everyone try it at least once is I treat my gas with 100% Acetone (2oz per 10 gallons) and try to buy only gas that is NOT blended with Ethanol.

 

I just watched a mythbusters episode this week that showed Acetone actually made the mileage worse on carbed and injected engines. I agree with the ethanol statement. It takes roughly 30% more ethanol to generate the same energy as gasoline. So beware all you E85 folks.

 

Ethanol has less power per unit of mass, so it wont go as far with all other parameters the same. It can tolerate more compression, though, so you could recover some of the lost fuel economy.

I usually manage to do low 20's cruising around. I did manage 28 or so doing straight highway, but with 2.77's and .68 OD, the car doesnt really cruise untill Im doing around 80+.

 

I watched the same Mythbusters and it's so biased to fail that I can't believe it. The ran the cars at a specified throttle position the entire time, and I didn't even see them run the fuel injected car. Mythbusters is a great show, but they don't always get it right. The gain in milleage comes from the part throttle cruise it takes less to keep the vehicle moving, don't believe me, give it a try. They also ran to rich of a mixture of Acetone vs. gasoline. I've also used acetone and low octane gas in place of 89 or 93 in my truck because it actually detonates less pulling hills with the Acetone mix than with the higher octane gas; plus it's cheaper.