MarcusF

It takes hours for an engine to cool down, so a 5 minute shutoff after reaching operating temperature will not impact the engine temperature enough to make a difference. After the restart, you’ll have full oil pressure within 10 seconds. At that point you can drive it however you want.

Regarding cold starts,
I start my car. As soon as the idle drops (15 seconds or so), I put it in gear and start driving. I keep the revs below 3000 RPM for the first 5 to 10 miles. That’s to warm up the oil. As stated in a previous post, oil temps are very important for engine longevity.

Another approach to warm-up: If I start my car in the garage, and let it idle until the coolant comes up to operating temperature, it will take longer [time wise] to warm up. That’s bad and here are two reasons why -

The entire time it is warming up, the ECU is running in an enriched mode. While in enriched mode, more unburned fuel than normal is passed through the cats. This is tough on the washcoat and can cause the cats to overheat. Both will shorten cat lifespan.

Also, the piston to cylinder wall clearance is greater until the pistons are at operating temperature. This is because piston expansion is greater than block expansion (pistons are sized with that in mind). This increased clearance results in increased blow-by. The blow-by pollutes the oil. This thinned out / polluted oil is tougher on the bearings than it would ordinarily be. Light driving will cause the pistons to reach operating temperature sooner.

I’d never allow any car I own to idle until it reaches operating temperature.

lizardjack

Well, the automatic transmission is a hydraulic unit. Oil temp. critical not less than the engine one's. I have STAR diag. and tested many times even after 15-20 minutes of driving, when engine T is 80+C, tranny is still at 50-60 range.

mikekuriger

I drive fast all the time. :-D I do wait for the idle to settle like everyone else though. Car is much faster when cold! 152,000+ miles and no issues

Budget Baller

As others have already mentioned I wait for the idle to drop. After about 10 minutes of cruising I'll usually drive a bit more aggressively.

I've always been pretty confident about the engine in this car...the tranny on the other hand... not so much. Though I only experience the 1500 RPM jerk I can't help but feel it's going to go out. It hasn't, but I always feel that'll be the down fall of the car. It may last many many more miles but I wonder every time I drive the car. That, if anything, is the reason I wait for operating temperature.

macbryanie

+1

AMG3.2

Yes, I am confident the engine will last a long time. It's the tranny that I am always scared about. I even sometimes regret the Eurocharged TCU tune because I know it has to be harder on the trans in some sort of way...

I had a Jaguar X Type before the Merc, and that car has a VERY weak transfer case. I could barely floor that 227BHP car without feeling like it was going to blow. Even members on the Jaguar Forum advised against driving aggressively.

I think this is the root of my transmission fear lol but then again I have heard that this trans is good for up to 500 BHP so who knows?




Now this is some good information. Thank you so much for sharing. This is exactly what I wanted to know.

Chedeng88

Since long idling turns out to be bad and granting that you want the car to hit normal operating temp at least every few days or so, what should owners of "winter garage queens" or those in storage do when roads are in a mess or wet for weeks because of snow?

I know for some it will be easily to say, "then drive it out when the roads sort of clear out". But taking out an extremely clean car from storage just to drive it out on wet roads for a few minutes, then clean it up again for re-storage will be a PITA.

Would it be okay to start the car and just rev it every few seconds to simulate load? The tranny might be a problem since obviously, just shifting through gears from a dead stop or even moving forward/backward for a few feet wouldn't really cut it.

I know this question only concerns owners with car OCD

AsianML

No, what's worse than what we've described here so far, because you're not even gonna be driving it afterward. At least those that are doing long idle warm-ups will be driving their cars. If you're gonna start it, you should drive it.

Chedeng88

So in cases where you "cannot" drive the car out for weeks, it's more beneficial not to start/warm-up the car at all?

AMG3.2

Yeah, I have heard that it is not good to start the car if you aren't going to drive it. My friend has been telling me that for months and I never believed him. It sucks because you technically should even start the car to move it which people do all the time. I do it when I wash the car. I pull it out of the garage and then pull it in. I'll have to come up with a different way such as driving the car, letting it cool for like 30 mins and then washing it. This way the car shouldn't cool down enough for it to damage anything.

Yes, this us for us car OCD people lol