The Bonneville that will.

[Phantom]

It has been some time since I was wanting to create this post but I have been busy finishing school.

I purchased an Emerald Green 1998 Bonneville SSE in January with 87,500mi on it and in good condition just needed some maintenance work. The car has a Series II Buick 3800 with the 4t65e transmission running the taller gearing (will add gear ratio when I remember). Features Heads Up Display, heated mirrors, auto dim rear, tire inflater, tinted windows, leather, and ride height leveling.
This car replaced my 03 GrandPrix that the fiancée is now driving to replace her Ranger.

My goals for the car are as follows:
(Completed)
Beat the avg mpg of the GP (23.6mpg)
Beat the best tank mpg of the GP (29.15mpg)
Beat the best tank distance of the GP (446.2mi)
30mpg tank (7/23/11)
Life time average 25mpg(9/8/11)

Goals to meet:
32.5mpg tank
500mi tank
35mpg tank or 621.4mi tank (1k km)
1000mi tank (If this happens I must have added an electric motor because I'm getting 55.55mpg!)


So far so good the car has no real mods just a few basic things:
Custom tune
Mild DIY shift kit w/ Dextron 6
Front poly end links
Gutted air box
Tires at 37psi (max sidewall is 40 and is slightly cracked)

Needed changes:
Replace worn/broken motor mounts
Fix AC clutch slightly drags when off
Add LEDs to display gear on dash and fan status
Mount Ultra-Gauge to dash and not window
Replace rear end links

Performance and fun
L26 UIM & Ported LIM w/ blocked TB coolant (5hp)
HV3 (20-30hp)
L67 TB no MAF post (5hp)

[Phantom]

Progress I had my best tank to date when on vacation a few weeks ago getting an average of 30.18mpg. This tank included city and mountain driving in Ashville NC for the first 80mi, then the first leg of the drive home with speed limits between 55-70mph mostly at 70. The average speed was 47mph. Also before I filled the tank the car rolled over 100,000mi what a way to celebrate.

I had not made any changes to the car that have not been on all other tanks before it. (airbox and tires at 37psi)

Now I have replaced my tires with "Bridgestone Potenza G 019 Grid" they allow for higher psi and have better handling than the old Michelin tires. So now I have about 47psi in the new tires and have achieved a tank at 29.88mpg both times I did this well I still had 3.5 gallons left in the tank.

If I get time I now need to start doing a few mods.

[grwulff@gmail.com]

I love the old Bonnevilles, great cars. I'm currently driving an Olds Alero with the 3.4 in it. It's pretty surprising how economical these old GMs are, eh.

[Phantom]

Just a quick update I have finally made it past 25mpg lifetime and over the last several weeks I have been getting ~27.x mpg per tank. On this last tank I only got 28mpg but almost reached the goal of 500mi on a tank only being 25.4mi short and having about one gal left. I need to put the factory belly pan back on and still have not modded it yet.

[99LeCouch]

Bumping this. I used to have a 1999 Buick LeSabre, and that car always got insane fuel economy for a large car. One incredible tank it got 39 mpg over 614 miles. That was a long, slow drive up I-95...

With the 2.86 gearing in it, its sweet spot for MPG was right around 55-57 mph. Your SSE with its 3.05 gearing is slightly slower.

That belly pan will help out nicely with mileage since otherwise a LOT of air is hitting the oil pan. Also, the L26 UIM is mainly cosmetic, and doesn't do anything a revised L36 UIM will do.

Enjoy your rolling sofa! I quite enjoyed mine the time I had it.

[Phantom]

I just filled today for 29.74mpg and was 0.7 mi short of 500mi and still had over a gallon left in the tank. There are a few changes on the L26 namely the material it is built of aluminum preventing the coolant leaking issues. Also It has a longer inlet with a round opening instead of the butterfly opening and a slight taper to increase velocity. There is a user test on this and it shows that the VE is increased a bit with the new upper intake. So if I am porting the Lower intake to remove casting flaws I might as well change the upper and add a less restricting Throttle body that matches the inlet opening.

To note I had the LIM from my 03 GP and purchased the UIM and new TB for ~$20 each shipped, the biggest difference I noticed when installing them was better throttle response. Also the reason for going with the L26 UIM is I purchased the HV3 (intake insert) for my GrandPrix with the L26 UIM and I want to put that in the Bonnie.

I like my FE but it is fun to press the Loud peddle.

[roosterk0031]

I'd went around the block a few times to hit 500, had my first 550 tank with the Stratus few weeks ago, had to go to station 1/4 mile out of way that morning to make it.