I whole-heartedly respect Steve’s wisdom without question or concern as he was exceptionally supportive not only during my search, but also after I made a purchase.

Being a mechanical engineer in the nuclear / aerospace / defense industries, there is one key phrase is his post (#4 referenced above) that caught my eye: “ ... when lubrication is at a minimum.” Even those with basic mechanical knowledge knows that operating bearings with minimal lubrication is a bad idea. However, since there is no way to easily check how well lubricated the thrust bearing is, prudence suggests assuming it is always low. Combining that premise with the additional knowledge that the less you use a mechanical system the longer it will typically last, it is now easy to see why the practice of not having to depress the clutch on start-up has its definitive benefits on thrust bearing life-expectancy.

Now, in an effort to help myself better understand the loads applied to the thrust bearing during start-up, how do these loads differ from those induced during regular shifting or holding the pedal down for a few seconds while waiting for traffic to roll after a green light? The only variable between those scenarios is the fact that the engine is running. Does the centripetal force of the driveline rotating reduce the clamping force of the PP thereby making the loading of the thrust bearing lower during shifting when compared to those at start-up?

Regardless of loads, I would think that since the frequency of using the clutch during normal driving far exceeds the use during start-up, it would have far greater impact on life-expectancy.

I am obviously not versed well enough in this scenario to render an official opinion and absolutely defer to Steve’s infinite wisdom. With that, apologies for getting into the weeds, and I’ll again blame it on the day job! Personally, I can’t get past the safety aspect of the interlock, but that’s just me.

Interesting counterpoint but I think I’ll keep starting with the clutch depressed. With decades of manual transmission driving as well as multiple manuals in the fleet, I am not going to try to change my approach for some cars. But interesting point to consider nonetheless.

In fairness, part of my die hard, “don’t turn the key unless the left foot is fully extended” rule dates back to starting my grandfathers car in the garage when I was 11 or 12 and having it lurch forward from the starter and nearly hit the wall. It was in gear and I had not fully depressed the clutch (it was a long reach for my legs at the time). Obviously that may raise the question of whether it is wise to let a child start and back out your car but this was a different time and place and it passed the smell test at the time. Thankfully no one saw me do it or my underage ‘driving’ privileges surely would have been revoked but it made an impression.

Two very different things though. I start with the clutch depressed 100% of the time and I hold the clutch at lights 0% of the time. I also don’t cover/ride the clutch while driving around (eg in between shifts) like some people seem to do. I spend very little time with the clutch not 100% released but I do for a second or two while starting.

I'm probably at 400,000 miles or so of manual driving and have yet to replace a clutch - including over 100,000 miles on a single car.

Absolutely agree with this. I don’t hold the clutch in for any longer than perhaps 3 to 5 seconds in any situation as I always felt it put undue loads on the system ... glad to know I was in-line with others on this.

The lawyers added the clutch interlock switch to our cars. One too many people trying to start their car (not necessarily Porsches) in gear with the resultant lurch forward. It was never required otherwise and never existed on cars prior to the 1990s.

I’ve owned numerous manuals, Porsche over the years and always depress the clutch before starting but always in N clutch out at lights with zero issues ever.