I just ordered a JL Rubicon and have been looking at the recommendations and warnings concerning fluids, additives, and cleaners. Will my 3.6L really puke its internals if I use anything not labeled Mopar? And I’m concerned about 0W-20 oil in a Rubicon. Some forums are recommending going to 5W-30. As for fuel additives, will they really damage my fuel system? Will an engine cleaner used before an oil change really destroy the engine? I realize the goal for Jeep is to make money, but what’s best for my vehicle?
Mopar would like you to believe that using anything other than Mopar branded stuff will wreak havoc and void your warranty, but your right to use whatever brand of fluid you choose as long as it meets the specifications is protected by federal law. This is the same law that prevents an OEM from voiding the warranty when a customer uses aftermarket replacement parts rather than dealer parts, and even protects many aftermarket modifications. In short, you’re free to use whatever brand you wish; just make sure whatever you use meets the required specs. Everyone seems to have a preference for a particular brand, but any recognized name brand that meets specs will work.
Running zero-weight oil seems frightening to most gearheads, but it’s the direct result of manufacturers trying to meet stringent fuel economy standards. The lighter the weight, the less drag on rotating parts, so fuel economy improves. But more importantly, the engine and its tolerances were designed around that oil weight, so we’d stand behind their recommended specs. Mopar has spent way more time durability-testing the 3.6L Pentastar than all of the forum and social media jockeys combined. Stepping up to 5W-30 would only make sense if you’re running fully loaded in extremely hot conditions all the time. If that’s not the case, just stick with the recommended weight.
As for fuel additives and engine cleaners, we’d be leery. There are a few decent products out there, but many are just snake oil and won’t do anything, and a few can even cause damage. We’ve had very limited success with using fuel additives and engine cleaners, as they’re often Band-Aids that just mask deeper problems for a while. They also are typically intended (and usually more beneficial) for older, high-mileage engines where tolerances are getting loose and prolonged use has caused the buildup of various deposits. In one or two cases we were able to clean up a random misfire or a noisy lifter with additives and cleaning products, but most of the time we’ve just ended up out the money and still had a problem.
The best thing you can do to keep your fuel system clean is to stay on top of the filter service, stay away from sketchy off-brand gas stations, and don’t let your Jeep sit for months without running it. The best thing you can do to keep engine internals clean and healthy is stay on top of oil changes and follow all other recommended service intervals. Sure, Jeep is in business to make money, but so are all those engine and fuel system additive companies.