baron95 wroteNo, I don't.I can't believe people are still repeating the old wives' tale about idling the car to let the turbos cool before shutdown. Are they deaf? Don't they hear the fan and pump going after shutdown on modern cars? My M2 does it plenty loud. My Jeep does it plenty loud.
I park meticulously and it always has the time to cool naturally. 
Redd wroteI have a 2013 M3 with the S65, an engine with known rod bearing issues. And I rarely warm up my car.Here's proof that you should warm up your car.
Top pic are my rod bearings at 90k kms shortly after I purchased it. The car was in generally rough shape and it was obvious the PO had not taken care of it.
Bottom pic are my rod bearings when they were replaced earlier this May 2026 after 80k kms / 10.years of use. The main difference - I always warmed up 1 min from cold start, at least 15-20 seconds from warm start, and I maintained below 3k rpms until oil temps reached 85C.
So yes, warm up your cars.
MJBO wroteShhhh...don't ruin his "proof".Everything in both photos looks shagged.
BruinMan wroteThere is a section on BMW manuals for "Highway Pulls"?What BMW generally recommends:
* Start the engine
* Wait about 10–30 seconds for oil circulation
* Drive gently until the engine warms up
The fastest and healthiest way to warm the engine, transmission, and differential is actually light driving — not extended idling.
Really cold freezing morning - 30 seconds to about 1 minute.
After hard driving or highway pulls, give the engine about 30–60 seconds of easy driving or light idle before shutting it off. That helps reduce heat stress on the turbochargers.
Redd wroteThat's not "proof" of anything.Here's proof that you should warm up your car.
Top pic are my rod bearings at 90k kms shortly after I purchased it. The car was in generally rough shape and it was obvious the PO had not taken care of it.
Bottom pic are my rod bearings when they were replaced earlier this May 2026 after 80k kms / 10.years of use. The main difference - I always warmed up 1 min from cold start, at least 15-20 seconds from warm start, and I maintained below 3k rpms until oil temps reached 85C.
So yes, warm up your cars.
Redd wroteAnyone who knows anything about E9x M3 and the S65 knows that the rod bearing problem those engines have, like the S85, is not due to failing to sit idling for 10 minutes before driving off or turning off the engine. I had a 2008 E90 M3 for 10 years and know a lot, and I changed the rod bearings myself as preventative maintenance. Most of the engine builders attribute the wear to the very tight bearing clearances, which are far below industry standards.Here's proof that you should warm up your car.
Top pic are my rod bearings at 90k kms shortly after I purchased it. The car was in generally rough shape and it was obvious the PO had not taken care of it.
Bottom pic are my rod bearings when they were replaced earlier this May 2026 after 80k kms / 10.years of use. The main difference - I always warmed up 1 min from cold start, at least 15-20 seconds from warm start, and I maintained below 3k rpms until oil temps reached 85C.
So yes, warm up your cars.
baron95 wroteMy M8 circulates coolant after engine shut down to cool the turbos. But I still will let the engine idle maybe a minute or two if the engine oil temperature/coolant temperature is elevated.The most important thing is to make sure the engine has reached full normal temperature for several minutes at THE END of the trip. If I need to drive a mile to the gym or the store, I will remote start the car, and or drive longer/harder as needed to make sure oil has full temp for a while before shut down.
Most people worry about the beginning of the trip (when should I start driving, etc?). The focus should be at the end (has the car run enough at temp before shutdown?).
P.S. I can't believe people are still repeating the old wives' tale about idling the car to let the turbos cool before shutdown. Are they deaf? Don't they hear the fan and pump going after shutdown on modern cars? My M2 does it plenty loud. My Jeep does it plenty loud.
pbonsalb wroteWith the engine idling the battery will not supply the electric power to run the fans and the auxiliary electric water pump.If you have just gone on a long drive and the battery is fully charged, will it continue charging during this file procedure or will the idle procedure just drain the battery a little? These cars essentially turn off the alternator whenever possible if voltage is sufficient to safely run the car without charging. After a long drive, the matter might be fully charged and the alternator decoupled. I do not know the answer.
RockCrusher wroteThis is the way charging systems used to work back in the old days. But these days, the alternator is turned off much of the time and the battery is used. This is a fuel saving measure adopted by Porsche, BMW and others; another one is specifying thinner oils. Then the alternator is turned back on during deceleration to charge the battery.While the engine is running the alternator supplies all the electrical power the engine/vehicle needs.
pbonsalb wroteI don't know about these days, but BMW promised the Efficient Dynamics feature of "brake energy regeneration" for my car (page 16 of the brochure) back then. And here is what it turned out to be: https://f20.1addicts.com/forums/showthread.php?p=30143985#post30143985. The alternator looks belt driven. How they would detach/attach it to the engine is most unclear.This is the way charging systems used to work back in the old days. But these days, the alternator is turned off much of the time and the battery is used. This is a fuel saving measure adopted by Porsche, BMW and others; another one is specifying thinner oils. Then the alternator is turned back on during deceleration to charge the battery.
pbonsalb wroteI was omitting the fact there was an electromagnet(ic rotor) that could be cut off inside the alternator.The charging circuit is disconnected so the alternator freewheels and there is virtually no drag when charging is not needed.
It's just not the battery 
but the rotor charging circuit is disconnected so the alternator freewheels.
BruinMan wroteAny 12v AGM will work [with appropriate specs]specialized AGM 12-volt battery
BruinMan wroteThe 2021 X5 M50i has 2 batteries. Maybe one of them is “specialized.” Perhaps that term defines its purpose as different from the starting battery? My 2018 M5 has only 1 battery and it is lithium ion. I think it still decouples the alternator much of the time and charges when coasting, braking or decelerating. I would call that more of a smart alternative control than regenerative braking. It is not like the braking creates energy that is turned into electricity. The charging while braking seems no more efficient than the charging while coasting or decelerating.I see some bad answers and some very good correct answers. This is what I found out for my X5.
2021 M50i relies on BMW’s traditional 12-volt Brake Energy Regeneration system.
How it actually works on your V8 M50i Intelligent Alternator Control:
Instead of a hybrid electric motor, the vehicle uses a specialized AGM 12-volt battery and an intelligent alternator management system.
Decoupling Under Load: When you press the gas pedal, the engine management system completely decouples the alternator from the engine. This ensures all 523 horsepower goes directly to the wheels without any parasitic drag from charging the battery.
Energy Capture: When you lift off the accelerator or step on the brakes, the alternator re-engages. It uses the SUV's coasting momentum to spin the alternator, capturing that free kinetic energy and routing it back into your 12-volt battery.
I hope this clears up some confusion.
pbonsalb wroteEngine braking does.It is not like the braking creates energy that is turned into electricity. The charging while braking seems no more efficient than the charging while coasting or decelerating.
But you (mostly?) need a MT for that. I read with AT (which is bullshit by itself 
) they (Porsche in particular, others too?) added coasting in neutral for longer range and fuel economy. 
Back then a car's manual would warn against driving in neutral as that affects car control (without electronic assistants) and brakes heating/wear too.
pbonsalb wroteNot to have a semantics argument here, but you're saying braking doesn't generate electricity then explaining how it does indeed create electricity.But while braking can create energy that can be turned into electricity, BMW’s so called regenerative braking is not doing it, at least on the older non hybrid cars. Rather, alternator charging is allowed during braking just like it is allowed on deceleration or coasting.
