Guys that have a L98 5.7 350 just seeing what gas mileage they get. I heard its 25 freeway 17 highway but i wanted to hear it from actually 350 owners what they get.

I have a v6 in my 91 camaro and i drive 60 miles a day to and from work. I just got a 350 to swap in after it gets rebuilt.

 

When I had my '87 Iroc (l98), I got around 15 city, 22 highway on 100% highway. It had some quirks which might have been the reason for losing some highway mpg, but my 2.8 got worse gas mileage then my Iroc so I couldn't justify driving the less enjoyable car..

 

205,000 miles, 5.7, 700R4, 3.27 rear.....I get 15/16mpg city, 21mpg highway.

And I can still light up the 315s!

 

I have an 87 305 TPI and I get around 16 mpg mixed. But I do have a heavy foot, and I really only drive the IROC on the weekends. Sort of a weakend warrior with it, so I'm not really in it for the MPG, I have a honda for that,...

 

Foot up or foot down?

 

should i rebuild my V6 or i found a l98 for 1500$ comes with everything still need to rebuild it tho.

 

i got 22 mpg highway on my last trip, no idea on city never have calculated, but 1500 seems expensive if you still have to rebuild, better off finding a donor car, and transferring everything over, engine, harness, tranny even rear end

 

Unless it's got a 6 speed bolted to it, it's not worth $1500 while needing a rebuild. I just picked up a 5.7L LT1 that doesn't need a rebuild with a 4l60 4-speed automatic, complete from front to back including radiator and fans for less than $1,000, so thats excessive for a L98

 

Mine gets 26 highway... that would be a place you can keep a steady pace, not LA. Around here, I was getting 21-22.

 

I can eek out 23-24 mpg on the highway if I cruise at a steady 65-70 mph. Around town, if I drive normally (which is like, never) I can get 14-15.

 

I never got more than maybe 16-17mpg and that was with a pretty light foot on cruise, 100% highway (60-70mph). Kinda jealous of the 24+mpg crowd here (especially with gas around $9 a gallon) I have the same combo as a couple above, 350, 700R4, 3.27s 9 bolt. No codes or weird issues, ran silky smooth only 70K miles on it.

 

thanks for the help everyone, im going to offer the guy 1100$ for his l98 5.7 its comes with everything needed for the swap he wants 1500$ so your saying 1500 is way too much because it wont even run so 1100$ or 1000$ would be fair??

 

Whut they are sayin is to stay away from that deal, due to it bein' too much of a headache an pain for an engine that does not work.

You can find one for cheaper and that actually runs for less in some instances. There are times you can find one with the tranny piggybacked to it...

Basically, why spend good money for somethin' that doesn't work?

Good Luck
Adrian

 

To swap a v8 into a v6 car, you don't want an engine, look for a cheap v8 car. You don't care about the body, but you want all of the brackets and bits that come with the engine install. There is very little in the v6 car that can be used with a v8. You will also need the v8 springs for the front suspension. If you look for a v8 car that needs body work, you should be able to find a complete car for less than $1000.00, maybe less than $500.00 if it is bad enough. You could even look for one with no registration and save a bundle because of the penalties the state puts on cars that haven't been registered. Since you will just strip the car and and junk what is left over, you won't be registering it anyway.

 

Wow I must have problems with my car, I am only getting about 10 mpg in town. 89 Trans am GTA

 

I'm willing to bet the problem with your car is heavy foot syndrom..

 

Not necessarily, an automatic tranny will use more gas, and if you are trying to drive in a big city, think the 10 biggest cities in the U.S., you may spend more time idling at lights than actually moving.

 

I am only getting about 8 mpg in the city when I romp on it and even still I am only getting about 10 mpg in the city when I drive normally. I know something is wrong with my car but I dont know what is wrong with it. Any possibilities on what it is? I can't check codes because right now my car is all tarped up for winter and it just snowed so any possibilities on what it could be?

 

Are you using an auto or t-5? Ive heard the autos kinda rev high at higher speed, and with a 2.73 0r 3.08, they have to downshift and unlock the tc alot. I have 4.10s and a t-5 behind my l98, and the thing revs at 1900@ 60, seems to be the same mpgs as my 2.8 was when it had 4.10s. I can shift into 5th @ 40 mph, and that thing climbs hills like nothing, i never really have to downshift, even to pass. so that works in my favor

 

I have the 700R4 with the 3:27 gears and when I am driving around town I never really hit any lights either so most of the time it stays in third or fourth. I get really good mileage on the highway (in the 22-24 range) because in forth gear at 75 mph it only revs to about 2500 RPMs.

 

I know this thread is kinda old but Im bored so, I just did a 280 mile round trip with about 20% in town and I averaged barely under 20mpg. On the highway it was on CC at 75mph. stock tuned up L98 with rebuilt trans and 3.27s. Im hoping injectors improve that some. I would love to get 24mpg on the same drive after that.

 

I tend to get 14-15 mpg city and 23 mpg on 100% hwy 70-80 mph. 700R4 with 3.23 rear gears.

 

Mileage is only a concern with cars that are not fun to drive.

 

I haven't checked yet, I have a L98,T-5 with a 10 bolt 3:08. Got a 9 bolt 3:27 in the final stages of a rebuild. Gas prices may have an effect on how long the 10 bolt stays on the car. Anyone have a guesstimate on my MPG with the 3:08? I can't drive mine right now due to a complete suspension upgrade.

 

You need a parts car for this swap a v6 car has different brake hard lines up front its more than just a motor swap to put in a v8 save some headache and buy a parts car.