I started this thread somewhat out of intellectual curiosity. I've had my start-stop disabled since I took ownership if nothing more because of the nuisance of the constant shutdowns. I was curious though as the majority of the info around start-stop systems involve government regulations and manufacturer compliance. I understand that manufactures are fighting for every bit of fuel efficiency they can get, that's nothing new, but I'm no conspiracy theorist and want to know FACTS about this system. Sure, it's stupid, but why ..
After some thorough internet searching, I've come to a few conclusions. First, don't trust what you read on the internet, lol. Even this post, take with a grain of salt. I'm just some dude. Second, not all systems are created equally. Like hybrid technology is totally separate from this conversation as that system is designed to go through these on-offs and will experience more starts-stops that our trucks for sure, so it's not all bad. That brings the most serious inquiry - how much have the 3.0 engineers done to incorporate the start-stop technology throughout the engine's components. There's a range that engineers do from just throwing on larger starters and calling it good to revamping whole systems. Sadly, I feel our 3.0s fail in this regard and aren't well adapted to auto start stop technology. The good news is our engines have had start-stop from the beginning with range rover (as far as I can tell) so if there were any egregious issues, we'd likely know about it. However, I've uncovered a few concerning things.
Mechanical versus a constantly driven electric oil pumps. One concern I had initially is accelerated internal bearing wear. Some vehicles (BMW for example) with stop-start feature electric oil pumps to keep this flow more constant. Our 3.0's don't have this. I've ran across a few bits of info online (one from a thermal systems engineer) that says that once the engine is at temperature, all lubricated and expanded, increased bearing wear isn't an issue then like it is at cold start. I can buy into that but that hasn't changed some manufacturers from going to an electric pump. I don't know how the automatic transmission deals with this either. I didn't find for sure whether our trucks use an electric pump and accumulator for the auto transmission. Maybe someone here knows but even assuming that is the case, that is another area of potential failure.
Mechanical versus a constantly driven electric water pump. This is another area that some manufacturers are turning towards to aid in the increased starts-stops. I worry about some sort of mild heat soak with the coolant not flowing as our 3.0s have mechanical water pumps. Heat is never good, which brings me to the worst thing ..
The turbo. Between the lack of oil at shut downs and no water cooling (that I can find) for the turbo, I just can't see how shutting the engine off constantly is good for that thing at all. I hadn't considered this initially but thanks to this thread I delved further and this seems to be the thing most affected by more stops-starts. I am aware that the stop happens when our engines are at idle and have idled for a second or two - better than a quicker shut off - but I really worry about the longevity issues here.
The one bit of good news is I don't feel the starter is an issue. It's a point of failure for sure but I do not feel the longevity issues will concern the starter. Starters implemented with auto start stop technology are much more complex and designed for the potentially 100,000ish cycles (as opposed so like 10,000 cycles) than traditional starters. There is a ton of information available online concerning starters in these systems and I trust the engineers can design and test the one critical piece of this puzzle. In fact, my issue with the starter is if the starter was to ever go, like they will likely do on all vehicles, we now have a much more expensive starter system to replace than the traditional starter. I've replaced a few starters in older cars and they're easy two bolt swap and not expensive, I usually get them from the junkyard actually for $40-60. Like most things with new vehicles, the shade-tree mechanic is left behind.
Always, enough on this. Anyone reading to this point I applaud you, lol. To sum this up, our engines don't appear to be designed with start-stop in mind. Some are and I do believe those engines may very well have no decrease in longevity, I truly believe that. Time will tell though. The mpg gains may be quite tangible for some car owners but likely not for us 3.0 owners as well so little gain here.
One last note: the engine coffee table book that is stickied on our forum is quite nice and helped in understanding all this, check it out!
