Not really sure if my car is considered poor in this department so thought I'de compare it to your guys and see if something needs to be done. Going to start by saying the long block is a 1990 L-98 with LO-3 injection stuff, I never got around to putting 350 specific electronic parts and injectors in it. I am using a stock TPI exhaust system for a 350 car. I'm also using a TPI fuel pump. The car has a 5 speed manual with 373 gears.

I've never done a pure freeway MPG check I'm basing mine on being stuck in traffic, driving around town on the weekends and light traffic. after a a fill up it is averaging between 16 and 20 mpg it's usually in the mid 17's though.

my car passed california emmisions test with ease so I doubt it is running on the rich side at all since all it's reading were well below averages on everything. My car does seem to lack power that it should have under loads but I figure that to be the lack of 350 specific stuff.

Sorry 305 guys but this is for the 350 guys only. can't compare a 305 to mine

 

Ive got a 92 caprice 9c1 probably weighs around 4,000 lbs. Its got the L05 350, auto and a 3.42 posi. I get 19-20 MPG in about 70% highway 30% city driving.

 

Just got back from Presidio in my 1983 G20. Pulled a 1987 GMC Jimmy on a trailer there and the empty trailer on the way back. I averaged 16 MPG for the trip with my 350 TBI/4L60/3.07 gears, I was doing 70 pretty much the whole way.

 

thanks guys

Sounds like mine is in the general vacinity of what it should be getting then 40 miles of my commute is pretty much gridlock almost so it's probably doing okay as far as fuel mileage goes maybe a switch to freeway friendlier gears would help it out alot.

 

my 95 silverado with 3.73s and many mods gets 15mpg in the city if I really behave myself. Have not done a highway mpg check yet.

Brian

 

mine got 23 on the highway and around 15-17 in the city with 3.73's
bone stock 350TBI engine and 700r4

 

20+ mpg highway in a 93 Buick Roadmaster wagon, 148k miles, 4500+ lb with bone stock LO5 (peanut cam) and 3.23 GU5.

 

18city/24hwy on 84 Corvette Crossfire with ZF-6 and 3.45 Dana 44.

 

15 city with a heavy foot, haven't ever really done any serious highway tests but the EBL reads 25 average highway with a light foot. 3.42's in a 4500 pound car.

 

10-12 mpg city and I REALLY beat the **** out of it. Every time I fill up I say "Okay, I'm going to baby this whole tank and see what my mileage is." After about 50 miles I say **** it and start flooring it left and right. I'm going to baby my next tank, I'll post up my results!