The 4.0L engine is likely the best known of all the Jeep engines ever produced. By the time it was discontinued in 2006 more than 7 million units had been sold worldwide and many owners have reported driving more than 300,000 miles without having to rebuild their 4.0L Jeep engines.Click to see full answer. Also know, which Jeep is most reliable? 10 Best Jeeps of all Time 2018 Jeep Grand Cherokee Trackhawk. We’ll start with a Jeep you can currently own – The Grand Cherokee Trackhawk. 2007 Jeep Wrangler Unlimited JK. 1997 – 2007 Jeep Wrangler TJ. 1993 Jeep Grand Cherokee. 1984 – 2001 Jeep Cherokee. 1976 – 1986 Jeep CJ-7. 1966 – 1971 Jeepster Commando. 1963 – 1991 Jeep Wagoneer. what year Jeep Wrangler is the most reliable? 2007 Also asked, are Jeep engines reliable? In conclusion, Jeep is not classed as a dependable brand. They were once very reliable, but this is no longer the case for a number of reasons. If you want a Jeep, the chances are you will buy a Jeep. And if you want a car that comes with as much history as that, then you can’t go wrong.Is the Jeep 3.6 a good engine?In general, the engine has been around for a long time and used in a lot of vehicles, so it has been well tested. Despite that they had some issues early on, the 3.6L V6 Pentastar is a great engine, one of the most reliable engines available on the market right now.