Horrible Mileage!!! Help!!!

OK so I bought this 1992 olds 88 for $200cdn. I fixed the passkeyII prob for $50 cdn, fixed the whining alternator, got it running on synthetic oil , got an aftermarket 2 stage foam filter, threw in a can of fuel injector cleaner, new plugs and wires, but my fuel economy is still bad. Im getting 350km(210Mi) to the tank on 91 octane. What do I do now? should I get the fuel injectors cleaned by my mechanic?... I am putting in a new fuel filter this week, but I dont think it will do too much. Maybe my engine is gonna go soon. I have 300,000km(180,000mi).

Yes 92 was the worst year for the 3.8 lifewise. Most only make it to 250 ,000 miles if taken care of.

Engine will be alright, I would worry about the transmission.


Lets see.

DO NOT USE BOSCH O2 OR PLUGS. bosch + 3.8L = bad news.


Replace plugs with AC Delco standards
Replace 02 sensor with AC Delco only not bosch, trust me on that one.

If it is lacking power I would look into checking out the cat.

is it showing any codes?

nope.... no codes... I just put a fuel filter in and did a fuel injector cleaning today... I will track mileage this weekend and see if it gets better... It can't get worse.... I hope. My tranny was recently serviced, but yeah it shudders into 4th... not bad though, I'm used to it now, I just ease it in. Maybe Ill add a can of no slip/shudder stuff.