Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's, Olds 98 91-96, Buick Lesabres and Park Avenue 91-96. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.
Post Reply
BumpinBonneville17
SLE Member
SLE Member
Posts: 51
Joined: Thu May 22, 2008 4:14 pm
Year and Trim: 1996 Pontiac Bonneville SE

Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by BumpinBonneville17 »

Hey guys,

For a long time I was getting like 16 mpg and everytime I started it she bogged and spit and sputtered and blew smoke for a few seconds until I gaver her some throttle and cleared the cylinders. The codes read crank sensor input so we replaced the crank sensor. That did nothing and we kept getting that *dang* crank sensor input code. So I bought a used PCM from the same year and trim car and slapped that in and now it starts fine and I'm getting like 5 miles per gallon better but still not the 25-30 which I figure I should be getting. I have not gotten a code yet since I installed the new PCM and everything is cherry except for the gas mileage. The last time I calculated it I got 21.5 mpg but I wasn't babying it while driving during that tank so this next time I calculate mileage I'm gonna baby it to see if its just my driving.

What do you think? :???:

Thanks,
Bumpin'
1996 Bonneville SE
Image
-20,000 miles on Brand New motor, 140,000 on car, Black Leather,
-Clear Corner lights, Gutted Airbox, Xenon High/low beams & Fog bulbs (all of em)
-2 12" Volfenhag Aluminum cone 500 watts RMS a piece DVC subs, 1000 Watt RMS Ultra Linear Amplifier, 3.0 Farad Capacitor, cooling fan for the amp, Kenwood Deck & 6x9's
User avatar
Wes
Posts like a Northstar
Posts like a Northstar
Posts: 2363
Joined: Thu May 22, 2008 8:09 pm
Year and Trim: 2002 Buick Park Ave
Location: Michigan

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by Wes »

Is that mixed, city, or highway?
Image
92 Olds 98. L67, Gen 3 M62, 2.55 pulley, FWI, PLIM, 1.8 YTs.
yourgrandma wrote:High
wjcollier07
Certified Bonneville Nut
Certified Bonneville Nut
Posts: 5647
Joined: Thu May 22, 2008 7:08 pm
Year and Trim: ____

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by wjcollier07 »

Well if you're drivin around with the 3.06:1, you're not SUPER gentle on it, and that is combined mileage, you're probably fine. I averaged between 21-24 in all three of my Bonnevilles, LN3, L27 and L36.
John
Now: '15 Toyota Prius III | 134 hp 2ZR-FXE | Silver | 36k
Now: '03 Honda CR-V AWD | Slow 4-Cylinder | Dirt | 180k

Then: '07 Ford Fusion SEL | 221hp Gen I VVT Duratec 3.0 V6 | Tungsten Silver | 150k
Then: '99 Toyota Avalon XL | 200hp 1MZ-FE 3.0 V6 | Diamond White | 189k | Sold: July 2015
Then: '11 Ford Fusion SEL | 240hp Gen II VVT Duratec 3.0 V6 | Ingot Silver | 84k | Totaled: Oct 23 '14 (Rear-Ended)
Then: '96 Buick Park Avenue Ultra | 240hp Series II L67 | Medium Dark Lichen | Bought: JAN 11 @ 135k | Accident: FEB 3 '12 | Crushed: MAR 1 '13 @ 153K
Then: '98 Pontiac Bonneville SSE | 205hp Series II 3800 L36 | Topaz Firemist | Bought: NOV '09 @ 74k | Accident: MAY 28 '10 | Crushed: MAR 15 '11 @ 84k
Then: '93 Pontiac Bonneville SE | 170hp Series I 3800 L27 | Dark Yellow Green | Bought: JULY '07 @ 92k | Sold: JULY '12 @ 118k
Then: '89 Pontiac Bonneville LE | 165hp 3800 LN3 | Medium Garnet Red | Bought: JAN '05 @ 117k | Sold: SEP 30 '07 @ 152k
freneticburn
Posts like an LN3
Posts like an LN3
Posts: 439
Joined: Tue May 27, 2008 10:23 am
Year and Trim: 1998 Bonneville SE?
Location: Maple Grove, Minnesota

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by freneticburn »

that's about what I get in my 98 SE (3.05 gears) mixed city and freeway miles, though mostly city miles with A LOT of stop signs and lights.
User avatar
Bugsi
Resident Gearhead
Resident Gearhead
Posts: 2405
Joined: Wed May 21, 2008 7:36 pm
Year and Trim: (RIP 10/31/15) 1997 SE
05 Mercedes S500 4Matic
Location: Sunnyvale, CA

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by Bugsi »

What final drive ratio do you have? (Check RPO codes in TechInfo to find out.) My car has the 3.06 and I don't get any better gas mileage than you do. With mostly highway going to work and back each week, I consistently get right around 21 to 22 MPG. On the drive up to WCBF, 10 hours of 100% highway driving, I managed 26 MPG and later 24 MPG. But I've never gotten more than around 22 on regular drive to work weeks. 19 MPG is common for me when they have winter blend gasoline, or if I'm not driving mostly highway.
PontiacDad at WCBF `08: "By any chance, was his name. . .Radomir?"

R.I.P. 10/31/15: 1997 SE: "Silver Shadow"
`05 Mercedes S500
BumpinBonneville17
SLE Member
SLE Member
Posts: 51
Joined: Thu May 22, 2008 4:14 pm
Year and Trim: 1996 Pontiac Bonneville SE

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by BumpinBonneville17 »

Wes wrote:Is that mixed, city, or highway?
Almost all city miles but a few 6 mile trips on the freeway here and there. I was just curious as to what I should be getting because I have seen numerous bonnevilles for sale claiming 30mpg and close to that. Also My brothers 1997 Grand Prix SE (3.8) gets around 27mpg although I'm not 100% positive on that number.
1996 Bonneville SE
Image
-20,000 miles on Brand New motor, 140,000 on car, Black Leather,
-Clear Corner lights, Gutted Airbox, Xenon High/low beams & Fog bulbs (all of em)
-2 12" Volfenhag Aluminum cone 500 watts RMS a piece DVC subs, 1000 Watt RMS Ultra Linear Amplifier, 3.0 Farad Capacitor, cooling fan for the amp, Kenwood Deck & 6x9's
User avatar
92BonneSE
Posts like an L67
Posts like an L67
Posts: 1385
Joined: Thu May 22, 2008 9:32 pm
Year and Trim: 2008 Aura XE
Location: Michigan
Contact:

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by 92BonneSE »

FWIW the fuel economy is "supposed" to be 19/city 30/highway

I average anywhere from 17-25 in the city. You just have to learn self control and stay out of the throttle, which is hard to do by the way. :twisted:
Image
2017 Cruze RS
2008 Aura - Totaled
Sold but never forgotten:
1998 Bonneville SE
1992 Bonneville SE
User avatar
Wes
Posts like a Northstar
Posts like a Northstar
Posts: 2363
Joined: Thu May 22, 2008 8:09 pm
Year and Trim: 2002 Buick Park Ave
Location: Michigan

Re: Getting only 21.5 miles per gallon on a 1996 Bonneville SE

Post by Wes »

yeah, if thats all city, then you're fine.
Image
92 Olds 98. L67, Gen 3 M62, 2.55 pulley, FWI, PLIM, 1.8 YTs.
yourgrandma wrote:High
Post Reply