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you & your car

2008 Jeep Wrangler Unlimited.

I own a 2008 Jeep Wrangler Unlimited and it is using a lot of oil. Can you please look into the excessive oil consumption of the Jeep Wrangler 3.8L engines starting in 2007/2008 models? Chrysler is saying that one litre per 750 miles is normal? It doesn't seem right. – Rudy

Consuming one litre of oil every 1,000 km or so is within generally accepted engineering standards for a high-mileage engine.

You do not say what the mileage is on your Jeep or whether the consumption has been steady or increasing. If the latter, there may be cause for concern.

Originally produced in 3.3-litre form in 1990, the 3.8-litre engine was the result of a longer stroke and bigger bore and first appeared beneath the hoods of the 1991 Chrysler New Yorker and Imperial. It remained in production for 20 years and was used in a wide variety of Chrysler, Dodge, Jeep and even Volkswagen Routan vehicles. Produced in Michigan, the engine was installed in millions of minivans alone until it was replaced in 2011 with the new 3.7-litre Pentastar V-6.

The 3.8 is generally considered a reliable and long-lived engine. As is the case with anything produced in such vast quantities, there are bound to be some that are on the outer edge of acceptable production tolerances. If only one per cent of all the 3.8s produced had a problem, that would be an enviable record by any engineering standard – but it would still mean there are at least 10,000 engines with a problem. That may be why you will find some reports of "excessive" oil consumption problems, even hundreds of them – but that is out of a body of more than one million engines.

But that does not address your particular situation. Some of the more common factors that can contribute to oil consumption are a clogged PCV or EGR valve or air filter or an excessively rich fuel mixture – often caused by a clogged air filter. Driving style, maintenance and how much work (towing etc.) the engine is subjected to can also contribute to increased wear and oil consumption.

One other factor that may be at play here is the way the engine was treated during the first few hundred kilometres of its life. With tighter production tolerances and higher quality lubricant,s we forget that properly breaking in a new engine and changing the filter after the first few hundred critical kilometres to get rid of any minute abrasive particles created during production, assembly or first use can make a difference in its life.

Door light

I read your response to the reader whose interior light would not come on when he opened the car door, but it worked when using the switch on the dash. You said the problem is with a small switch on the door post of the car that operates the light. I have a Lexus RX300 and it does not have a visible switch for the interior light on any door. My interior light only goes on when I open either rear door but neither front door. How can I fix this? – Dave

The answer is the same, the location and visibility of the switch is the difference. You have to find the switch or sensor that tells the control module a door is open. In some vehicles, this sensor/signal activates a warning light on the instrument panel. Look for this light when operating all four doors and the hatch individually to see if one or more do not function. It sounds like the rear doors and hatch systems are working, so you will need to locate and replace or perhaps lubricate those for the front doors.

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