The owner of this 1998 Oldsmobile Eighty Eight LS has some concerns about what maintenance he should do to his 200,000 mile car.
This weekly Q&A session answers your questions about cars and trucks. This week explores maintenance tips, plenums, and additives for a high-mileage 1988 Oldsmobile LS.
Question: 1998 Oldsmobile Eighty Eight LS
Hello Vincent:
I have almost 200,000 miles on my car. Fortunately, I have an excellent mechanic from the old school who is up to date on things and doesn't rip me off. The car runs excellent:
- Are there any specific maintenance tips or things that should be checked on a car with this many miles on it? If there are some specifics, I could share them with my mechanic. I change the oil every 3,000 miles, change the transmission fluid every 30,000 miles, etc.
- I almost thought I would need to get a new car. The Plenum went bad and radiator fluid got into the engine recently. At about 100,000 miles before, the same thing happened. The mechanic replaced it and the engine was fine. Now, with close to 200,000 miles on the car, the mechanic was hesitant about replacing the plenum because he couldn't predict the damage to the engine.However, after checking the compression and knowing I took very good care of the car, the mechanic went out on a limb and changed the plenum and predicted that the engine would be okay. After 2 weeks, he replaced the oil again and used Marvel's Mystery Oil. It paid off. There appears to be no damage to the engine and the car runs excellent.What exactly is the Plenum? I understand on these cars, the Plenum has a tendency to go bad
- What do you think of B-12 Chemtool as an additive? Are there any additives that you would recommend I add to the gas tank?
Thank you,
John
Answer:
The best thing to do, John, is to stick with the mechanic you have. He seems to know what he's doing and is honest. As long as he does right by you, you won't have any problems.
- As for maintenance, you seem to be on top of it. As it gets older in age, keep an eye on the brake and fuel lines that run under the car for rust. Also rust in general. If you find any, fix it quick since once it starts, it gets worse fast. More so in the "salt belt" of the northern portions of the country.
- If you have a GM 3.1 or 3.8 liter V-6, you will have to replace the intake manifold gaskets. See GM Intake Manifold Leaks and GM Plastic Intake Manifolds It's a fact that GM is having a lot of problems with them. In fact I have been hired as an expert in a class action lawsuit against GM for this. Reading these 2 articles will explain what a plenum in. Basically it's the technical name for the intake manifold. This a 2-piece manifold, upper and lower, that has gaskets between the 2 pieces and cylinder heads that fail quite often.I just did the intake manifold gaskets on my girlfriend's 1997 Buick Lasabre with 125,000 miles and I'm in the process of writing an article outlining the damage done when they fail.
- I'm not a big fan of additives. I have found very few that work or do as they claim. I have used the BG line of products and have found they generally do a good job, especially their fuel treatment. But basically use a good quality fuel, change the oil and transmission fluid as you have, and you won't need any additives.
That’s all for this week. Feel free to browse the archives for past topics.
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