I have a 1988 fleetwood brougham. i recently replaced the spark plugs, wires, distributor, cap, rotor, O2 sensor, egr valve, air filter, fuel filter, pcv valve, and vacuum lines. I am still only getting 10-12 mpg. if anyone else has an '88 can u tell me what u get, or give me some more ideas on how to get my mileage up. anything will help . thanks

I am in the same boat as you!

I own a '94 Fleetwood, I have been easy on the gas pedal, usually keep speeds of 45-55 MPH, and some how Ive gone 140 miles on half a gallon of gas, which calculates at this point 12-14 MPG for my 5.7 ltr V8.

It feels like a semi starting off while Im doing 4-8 MPH, like Im letting the clutch out and starting off.

Today my engine sputtered while doing 3-4 MPH pulling into a parking spot, I thought I was going to stall. The engine RPM's were dropping and raising back up, then it went up to normal, strange as hell. I have 107,000 miles and I think its time for a tune up, plan on replacing:

PCV valves, the 2 oxygen sensors, spark plugs, cap and rotor, ignition coil, plug wire, and possibly the air filter.

I have a 1988 fleetwood brougham. i recently replaced the spark plugs, wires, distributor, cap, rotor, O2 sensor, egr valve, air filter, fuel filter, pcv valve, and vacuum lines. I am still only getting 10-12 mpg. if anyone else has an '88 can u tell me what u get, or give me some more ideas on how to get my mileage up. anything will help . thanks

i have the olds 5.0L which is does not have enough power to move this car like the LT1 would (140hp vs. 260hp). but when i am easy on the gas i get 10-12mpg, same if i floor it from every stop sign and stoplight. according to carfax, this car has 189,000 miles on the clock, although i highly doubt that given the condition of the car, no rust and the engine runs perfectly. the only problem is its amazing ability to make the gas gauge drop as you drive around town. i usually get about 140 miles to a half tank as you said, and its a 25 GALLON TANK! i have the 200-4r which should give me good mileage considering most speeds are 40+ and the overdrive ratio is .67 or somethin like that. i must have a hole in the gas tank. lol
anyways, what other parts could i replace to help my mileage?

I have the same problems as carguy as far as the sputter and stall, but, my problem seems to be internal engine.

Two totally different engines but both "may" have the same problem. Prior to a complete tune-up, I'd have a mechanic check out the ignition secondary system with a scope to pinpoint any obvious problem(s) (the canister purge valve is a common problem on the 307, and you might have a carburetor problem) then do the tune-up, paying special attention to any components that the scope indicated were bad. If you have an LT1 engine, a "cap/rotor" is a tall order and usually I tend to suggest replacing the entire Opti-Spark distributor, while you're at it, I'd replace the waterpump too. The Olds 307 was a little under-powered I'll agree but it could give you a solid 20MPG highway. The LT1 while being a huge step forward in power, ALSO manages at least 20MPG highway. With stock gearing, 25MPG or so is not uncommon out of a LT1 car. 15MPG or so around town is also reasonable on the LT1 either engine. I recall we got similar mileage out of both engines but the LT1 just gave us way more power while doing it! ;)

I have to say, being one of the leaders in mileage, right behind the leader ssstealth, Cap and rotor become cructial as you rack up mileage. Tune ups are only so good after a while because you burn so much oil and run so inefficiently.

I found a distributer cap/rotor for $129.00 and the ignition coil for $29.00.

Now, along with that, I think I found a distributer for $200.00 or $300.00 bucks, at gmpartsdirect.com, is this accurate???

Why replace the distributer???

Its amazing, I tell kids at school that I have to pull my water pump to get to the items to perform a tune up, and they tell me its no big deal. Just pull the bolts, and then the water pump and your basically in, thats before you drain the system of course.
Two totally different engines but both "may" have the same problem. Prior to a complete tune-up, I'd have a mechanic check out the ignition secondary system with a scope to pinpoint any obvious problem(s) (the canister purge valve is a common problem on the 307, and you might have a carburetor problem) then do the tune-up, paying special attention to any components that the scope indicated were bad. If you have an LT1 engine, a "cap/rotor" is a tall order and usually I tend to suggest replacing the entire Opti-Spark distributor, while you're at it, I'd replace the waterpump too. The Olds 307 was a little under-powered I'll agree but it could give you a solid 20MPG highway. The LT1 while being a huge step forward in power, ALSO manages at least 20MPG highway. With stock gearing, 25MPG or so is not uncommon out of a LT1 car. 15MPG or so around town is also reasonable on the LT1 either engine. I recall we got similar mileage out of both engines but the LT1 just gave us way more power while doing it! ;)

the engine runs like brand new, and burns no oil. anyhow, the other day i was replacing vacuum lines and when i went to run the car, the check engine light came on. i checked the code and it was for the canister purge solenoid. what is this/what does it do? why would it be causing me to get bad mileage? thanks for the replies.

The solenoid controls when the vapor canister is being purged. If it's being purged at the wrong time, the engine will run poorly. It's also possible to have the system pulling raw fuel from the vapor recovery system and that will kill your MPG.
As for the LT1 distributor issue, the cap/rotor are always a good idea but the main problems with the Opti-Spark system are:
1. Corrosion due to vent system failures
2. Optic sensor failure
3. Timing wheel seperation
4. Corrosion of the harness connector due to weatherpack seal failure
None of these issues are touched on by doing the cap/rotor R&R. So since the distributor is NOT extremely easy to R&R, and the replacement price is NOT significantly greater than just doing the cap/rotor, I've always done the distributor instead. BTW, your friend is correct, the water pump IS pretty easy, although on some applications, it requires a little more accessory removal than on others.
I also forgot to mention yesterday that the coil wires are notorious for failing on the LT1's as well, especially on the gen 1 design (pre' 1995 as I recall). When inspecting for this issue, make sure to inspect the coil and cap connections, they tend to fail due to corrosion.

is the canister purge solenoid hard to replace/expensive and where could i pick one up? the local autozone? also, the check engine light will only come on at startup and stay on for a few minutes. the time changes with weather conditions/temperature. does this mean that the solenoid is working part of the time?

To be honest, I'm not sure. I think it's a dealer-only item. The timing of the failure "may" have something to do with the type of failure but I'd bet it's just due to that being the "programmed-in" operating schedule of the solenoid. Oh, and it's a real easy swap.

alright, thanks for the help, the "programmed in" schedule makes sense for the cause of the light turning off. well, so far thats the only problem i've having. i'll go and check out some dealers and look online. and again, thanks for the help.

Is the oil burning notorious in the 307? What can I do to help? A mechanic friend of mine turned me on to an additive called Seafoam. Very good stuff. Cut down on the smoking dramatically! However, at oil change I notice more smoking and I need to pick up some more. By the way, Carquest is the only place I have found this Seafoam for anyone interested.

I always get better mileage when I fill up with premium, but I don't think that would account for mileage that bad. And yeah, 307s love their oil. Use the heavy stuff scottie. I'm running 20-50 and the problem is almost non existent around town and minor on the highway.

well, today i found out that my odometer is off by about 40-50%, so that should help my mileage a little bit. other than that, i checked the oil today and i was a FULL 2 QUARTS LOW. yikes. i am using penzoil 10W-30 should i go thicker or stay with this. i think i am going to replace the valve cover gaskets, so until i do that i guess i'll stick with this oil