The SSEi gets ~24 highway, 18 city.
The GTP gets ~16 City, 35 Highway.

Yeah, I was suprised too.

I never get worse than about 25Mpg on my 97 SSEi, and thats around town in cold weather. I commute 70 miles to work each way, and its almost all highway miles, and I constantly get 30Mpg. I have the cruise set on 70Mph most of the way.

My 92 SSE only gets 25 on the highway. I know it has serious problems though, it used to get a lot better.

I'd say if you have a Bonnie and are getting less than 27 on the highway, I'd be looking at a tuneup, or at the least, a new O2 Sensor.

Cheers,

Andrew

Well until I have started playing with my mods, I WAS getting 20-30 (city/highway) WITH my ankle in the TB...

Now...about 17-27.....still with the ankle in the TB\


All in All....still happy....better than my T/A used to get....(8-12)

Hmmm....I wonder about those higher reported numbers, too. The stickers on my 2 Bonnevilles ('92 and '93) said 16 MPG city, 26 MPG highway, and that'* roughly what they get.

Are some of you guys using the "new math" ?
Or are you calculating the MPG without filling the tank completely for the trip starting and ending measurements, i.e. are you letting the fuel nozzle shut off automatically so you know that the tank is full?

My '93 SSEi has only gotten around 16 MPG in city driving since I bought it 4 1/2 years ago. It'* had tune-ups and several other new parts, and has a brand new Delco oxygen sensor. It always starts right up, runs smooth, and has plenty of power. Why is the MPG so much lower than some of yours? My wife drives this car, and she drives like I do - smooth starts and stops, nothing erratic.

And my '92 SSE */c gets around 18 MPG under the same conditions, but I suspect that might be because its engine was rebuilt 50k miles ago at 100k miles...although this car drinks oil but the '93 doesn't, and I think that the engine on the '93 has never been rebuilt and it has 142k miles.

I understand what you are saying about the fuel shutoff. I fill mine till it shuts off, then round up to the next dollar. I have been doing about 700 miles every week for the last 6 months, and i always average 30Mpg. Some times its 29, sometimes its 31. Thats the SSEi too.

>I understand what you are saying about the fuel shutoff. I fill mine till it shuts off, then >round up to the next dollar. I have been doing about 700 miles every week for the last 6 >months, and i always average 30Mpg. Some times its 29, sometimes its 31. Thats the >SSEi too.

Now I really feel left out...wanna trade cars? Just kidding.

So why does our fuel ecomony vary so much? Anybody have any suggestions on what I can do to get better fuel economy on both of mine?

If I knew what was causing my 92 to get worse, then I would fix it. I changed a few things, including the O2 sensor and they didnt do anything.

The only thing right now that I can guess at is the thought that the transmission in my 92 is slipping, and causing more gas to be burnt. But I really dont know. I cant imagine 6 or 8 Mpg difference from tranny slippage, especially when its not very bad.

See, even mixed driving, 50/50 city and highway I get about 26 in my SSEi. I cant explain it, but I do like it.

Can anyone shed light on what could cause fuel economy to go bad, aside from the obvious like tuneup and O2 sensors ?

Cheers,

Andrew

The best I ever get with my 92 SC is 24 on the highway, probably 17 city. With ACDelco plugs & wires, as well as with Iridium plugs MSD wires and same O2. When I first bought it, it was 20 no matter how or where I drove.

BTW, my 92 SSE has done 135k miles and my 97 SSEi has done 92k miles. Both on original engines and trannies.

I cant be the only person who gets great economy out of their bonnie can i ?

THis is what our cars (previous and now got)
1988 LeSabre Vin C N/A 25 mixed driving, 27 highway
1992 Bonneville Vin L N/A 26 Mixed 30 highway
1995 Bonneville Vin K N/A 28 Mixed 32 highway
2000 Bonneville Vin 1 */C 24.5 Mixed 28 highway (D.I.C. reported)
1997 Riviera Vin 1 */C 26 Mixed 29 highway