Reader Question: Sir,
I have a 2001 Jeep Wrangler with a 4.0-liter engine (5 speed Manual transmission). It has 93,000 miles and runs great! It has always gotten about 14 MPG on the highway. The repair manual says to replace the spark plugs every 30,000 miles.
Most of my shade tree mechanic friends say it is unnecessary to get a tune-up every 30,000 miles. Is that true with today’s car? It seems dealers try to make their money on “unnecessary services” these days.
Also, what is your opinion on oil changes. Is 3,000 miles to soon with today’s oil/cars?
I think 30,000 miles is a little premature to replace spark plugs. I would recommend a tune up about every 60,000 miles unless there is a problem that warrants doing so earlier. 14 MPG on the highway is pretty low for that vehicle though. I would expect to get 18 MPG at least.
Replacing the fuel filter, air filter, spark plugs and spark plug wires MIGHT help to improve that mileage number some…maybe! Maintaining proper tire pressure and using the correct weight engine oil could also help improve fuel mileage.
If this engine is equipped with a distributor I would have your mechanic check the ignition timing and advance or increase the timing a bit if he can to help improve overall performance.
Checking the ignition timing used to be part of a tune up, but these days a tune up usually means just replacing the spark plugs. Most cars are completely computer controlled and you cannot manually adjust ignition timing like you used to.
For lack of argument, because there is always a lot of argument about oil change intervals, I still prefer to change the oil and the filter every 3,000 miles. You can read ALL about motor oil and the reasons why you do not need to change your oil that often (if this really interests you) from this link and there is an ebook, which you can download.