Break-in Your New Car the Right Way

News from Detroit says that Chrysler Group sold 25% more vehicles in 2011 than in 2010. Good news for our brand and good news for the people buying new cars and trucks. Since auto sales are up across the board, it seems as good a time as any to talk about one of my pet subjects, breaking in a new vehicle. I first learned about break-in methodology during my training for my FAA Powerplant license, and I have spent 30 years since increasing my knowledge base. If you are lucky enough to be buying a new Mopar car or truck, then let me pass on some advice.

Late last year at a local test and tune, a young gentleman was present with a new Challenger. And by “new” I mean right off the dealer’s lot the night before. It seems the guy wanted to get some baseline numbers on his car. I asked him how many miles it had on it and the answer was some low two digit number. I tried to talk to him about how it wasn’t a good idea to put the pedal to the metal for a quarter mile in a vehicle that wasn’t broken in yet. His response was, “You have to drive it like you stole it right from the beginning. Break it in hard and the car will be ‘loose’ and always make the most power.” Sigh.

OK, rule number one, ignore that guy! If you care about getting maximum life and performance out of your new car or truck, then break it in correctly. If you don’t mind if the car is smoking and leaking and has a noisy rear end by the time the odo turns 50,000, then go ahead and ignore the following advice. Remember that you’re breaking in the whole vehicle: engine, transmission, rear end, brakes, etc. The methodology presented here is holistic, taking the entire vehicle into consideration.

There are two primary concerns for break-in, mechanical (parts moving and wearing into each other) and thermal (heating and cooling cycles that heat treat or stress relieve metal). Both concerns require time and mileage.

During the first 50 miles, critical mechanical break-in (wear) is occurring between your piston rings and their cylinders, your camshaft and its tappets or lifters, your connecting rods and crankshaft and their bearing surfaces and journals, and of course your transmission parts and rear end gear set. In a brand new car, as amazing as modern machining techniques are, there are microscopic high and low spots on various parts surfaces. These micro high spots can cause very local increases in friction (and thus heat) until the molecules of the mating surfaces have moved around and accommodated each other. If you take it easy on the car, keeping the overall temperatures reasonable, then no worries. If you go zooming around at high revs and full throttle before they wear in, then it's bad, bad news.

For The First 50 Miles:

  1. Do not exceed 50% of the engines rev limit (if it redlines at 6,000 rpm, stay under 3,000 rpm).
  2. Do not exceed 1/4 throttle unless there's an emergency (if a truck is about to hit you, the heck with the car, floor it and get out of the way!).
  3. Use the brakes gently, again unless there's an emergency. Look ahead, drive easy and brake slowly and evenly. Avoid hard use of the brakes if you safely can. You have to heat cycle the brakes for awhile to achieve maximum braking efficiency.
  4. If you have a manual transmission, shift gently. Don't force the trans into gears quickly, you've got to wear in the synchros for a while. Don’t slip the clutch too much, it needs to both wear in and heat cycle for a while.

Avoid cruising at one constant speed. Your car's engine needs variable RPMs and pressures during break-in. You don’t want to drive from the dealer's lot onto the freeway, turn on the cruise control, and just motor down the highway at a steady and constant state.