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Severe Driving Conditions

It’s commonly noted here and many other places that stop & go driving for short distances is more wear on your car than high mileage freeway driving.

It is also commonly noted that the Toyota Prius is the most fuel efficient vehicle, especially in city driving.

So here’s my quandary - The gasoline engine in the Prius only kicks in when its speed approaches 15 mph.

If you apply the ‘stop & go driving is bad for your engine’ logic, for people who drive mostly in cities and suburbs, the Prius’s gasoline engine should be having more problems than the engine of the average gasoline powered vehicle.

According to Consumer Reports and other sources, the Prius is one of the most reliable vehicles on the road.

The Prius has been around for over 10 years, so you’d think we’d be hearing about engine problems in many of them by now.

I haven’t.

So, why is the Prius seemingly exempt from the problems caused by stop & go driving?

Or is stop & go not as bad as we are led to believe?

Just what kind of “problems” from stop and go driving are engines other than the Prius having?

Stop and go doesn’t cause bearing failure,headgasket problems,valve train failure.

Stop and go is a mpg concern, I acknowledge more stop and go cycles do use up the number of cycles that driveline components potentialy have faster, but I feel is like saying “your wearing out my TV by watching it so much”

Stop and go traffic is hard on a car because the engine spends a lot of time idling.  Idling is not what an engine is designed to do.   The Prius (I believe) stops the engine when it is not needed and restarts it when needed using a starter that is designed for the duty cycle it has.  

Part of the reason that manufacturer's call for more maintenance under "severe" conditions is because the engine run time is greater due to idling per mile than on the highway.  They need to adjust for that idling time and for the fact that when accelerating it is working harder than just maintaining speed.

One problem with stop & go driving I’ve read about here and other places is that it can cause engine sludge. ‘Stop & go’ is also considered to be a ‘severe’ driving condition. I don’t know what the oil change interval recommendation is for the Prius, but I doubt if it is the 3,000 miles or less that is recommended by some for those severe driving conditions.

I was hoping this topic would lead to a discussion as to whether short trips and stop & go driving has ever been proven to be a problem with gasoline engines.

I’m not a mechanic and I don’t really know the answer. In my own experience, I’ve not seen evidence that low mileage stop & go, short trips are bad for a car’s engine.

Maybe I’m missing something. Is it not the engine that one needs to worry about, but other parts that are more affected and likely to have premature wear?

Idling is definitely one of the conditions taken into account when designing a automobiles engine.

Skipping oil changes causes sludge,poorly designed engine coolant passages can accelerate the sludge condition.

Really extensive idle time (police cars) can lead to odd cylinder surfaces or premature camshaft wear,but this is the extreme,not stop and go driving.These conditions are from years past, materials and lubricants have greatly mitigated these conditions.

Your Prius also shuts down the engine when you stop at a red light if you are not running the air conditioning, right? Also, the engine’s main job is to charge the batteries, not propel the car. So your engine is very different from the average internal combustion engine and has a starter that is designed to start the engine many times in a single trip.

However, that only addresses the engine, not the drivetrain components. Stop and go driving is hard on the brakes, suspension components, and drivetrain.

The owner’s manuals I have seen define severe conditions by both use and ambient temperatures. If you drive in a really hot climate or a really cold climate, that would dictate severe conditions regardless of the type of driving you do.

The main causes of engine wear in stop and go driving (as opposed to highway driving) happen from idling and because the car must repeatedly accelerate instead of just maintaining a constant speed. Your Prius engine doesn’t do much pushing of the car. The electric motor does most of the pushing. The electric motor does all the pushing if you accelerate moderately.

In your Prius your engine works as a generator most of the time rather than as an automobile engine. That is why you have nothing to worry about.