ranesh

I always thought it was conventional wisdom to warm up a car (any car) engine for a minute or two before driving. This was backed up by the results of the Boxster Engine Failure Survey where engines that were not warmed up before driving had a higher failure rate. However, the Driver's Manual of my 2004 Boxster says explicitly that I should not warm up the engine while stationary but should drive off immediately but keep the engine speed low till it reaches normal operating temperature. (Interestingly, my friend has a MINI Cooper and her Driver's Manual says exactly the same thing.) I would be interested in finding out what rennlisters think of this conflicting advice.

Doug Hillary

Hi,
the "conventional wisdom" has actually always been (for at least 6 decades that I know of) to start up and drive off as soon as OP is correct and all else has been found to be functional. Keeping revs to a minimum (say below 3000rpm) and with normal "loading" of the engine creates the quickest way to reach a "normal" core engine operating temperature. Excessive engine revs when cold can place enormous strains on engine technology/metallurgy

Some Porsche engine families can take up to 20minutes or more to reach their core temperature

It is important to get the oil's temperature above around 50C as soon as possible (typically oil trails coolant by around 20C) until an equibrium has been reached. This core temperature is around 90-95C. Anti Wear (AW) additives activate at various "elevated" temperatures and up until around 50C most AW protection is via the boundary wear additives left at cool down. According to the cold start characteristics of the lubricant being used (0w is best) some lubricant will also remain unfiltered due to the differential by-pass function of the oil filter until it reaches 40-60C or so

Regards

fast1

Fuel injected engines do not require a warmup period prior to driving. When engines received their fuel from carburetors however, a warmup was required to prevent stalling. The only caution with fuel injected engines is to run well below redline until the engine has been given a chance to warmup which typically takes less than 10 minutes.

I don't know of any engine that would take 20 minutes to warmup, so I'll defer that case to Doug since he brought up that example. My E46 M3 had amber LEDs adjacent to the red LEDs on the tachometer that were illuminated when the engine was cold. It took approximately ten minutes for all of those amber lights to go out, and then only the reds ones remained illuminated.

First986NJ

Also, If I recall correctly, the Boxster engine failure survey indicated that failures were higher primarily on cars that were not properly warmed up before being driven in cold weather conditions - an important distinction.

The car should be started and driven without any prolonged idle period. The revs should be kept below 4000 until the engine shows full, normal operating temperature. How long this takes is going to vary with engine size/type and the driving conditions encountered during the warmup period. Frequent stop/starts, for example, are going to put heat in the engine a bit quicker than open road, low rev driving.

986Jim

The problem with the boxster engine failure survey is that everybody with a problem flooded to that survey. How many people never come to the internet or come to Porsche forums that own a boxster? There have been over a hundred thousand made to date, all the people on all the boards are only 10% of that or less with boxsters.

Also when somebody has a problem with the car whats the first thing they do? They google it and find sites like this where people talk about it. This skews the results and people who are mad also give results worse than they really are or paint the scenario to be more grim. When there is a problem people coming looking for an outlet to vent about it. How many new users show up on all the Porsche forms and their first post is a problem we have all answered 1000 times before?

Engine failures of a particular kind are very common on many cars. The 2ng Gen Eagle Talon had crankwalk and that was blown way out of proportion to the point where guys sold their cars because they were worried about it. Ridiculous. The MKiV Supra has also had engine crankwalk problems also blown way out of proportion. RX7's people say the rotories blow up every 50k but there are tonnes of them with 150k on them totally stock that are fine. Again more internet wisdom shining through.

Basically what it boils down to is that survey is not really accurate and even worth considering as so many of the answers came from guys with failure. If we had the other 90,000 boxster owners chime in who never heard of Rennlist and the engine failure survey guess what would happen to those results?

Failure results on particular models has been happening on the internet a million times before on a million different models before we even knew there was a "problem". None of them were ever accurate or ever amounted to anything and this "boxster failure survey" is exactly the same thing. Been there done that with 3 other models before this car.

Just drive your car per the manual and you will be fine. In the off chance you do have a failure, don't blame the motor or your driving. Every car has failures to a percentage of the population. You roll the dice and thats it, ask Z06 owners...

First986NJ

I agree with that for the most part, but not completely......

The survey only indicated about an 8% rate of catastrophic failures, and that was inclusive of both sleeve related failures and intermediate shaft bearing failures. Since there were over 250 respondents, I don't think you can say that it was only guys with failures who responded. Statisticly, it would appear to be a valid sampling. However I do agree that the data is probably skewed somewhat by the distribution of the model years of the cars owned by the respondents. Only 25% of the respondents owned pre-2000 models, the period of known concern, while more than 68% were owners of 2001 through 2003 models. Even so, almost 80% of the catastrophic failures reported were on 2000 and earlier model years.

So, what I took away from it was that the data indicates that the overwheling majority of the catastrophic failures occured in pre-2001 models, and that on 81% of those, the owner indicated that they did not normally warm the car up properly. I found that to be pretty interesting.

Ray S

Actually, that's not true. Just because they got a relatively high number of responses, the sampling was far from random. To have any real confidence in the results the sample would need to be a random sample of the population (all Boxster owners). This did not occur.

The other posters concern about owners with problems searching out answers and then finding the survey on sites like PPBB or Rennlist is valid. Obviously many search out these sites for other reasons as well, and many with no problems also responded. The data is obviously skewed, but which way and how much is impossible to determine.

What you end up with is a survey that while interesting to read has zero credibility if you try to extract any real data. Garbage in, Garbage out.

First986NJ

I don't agree. I'm not sure I see how you figure the sampling was "far from random" ? Unless he limited the responses, or solicited a select group of owners (neither of which he did, I'm fairly certain...and the data doesn't hint at that either.) how is the sample not random? It was posted on a public discussion board...for one thing. Your assuming that a specific group responded more heavily than another. I don't see where the data supports that.

Jay Laifman

You guys are getting into an argument that has gone around and around countless times. The last time, I recall multiple professional statisticians showing why Ray is correct. No sense in rehashing it again really.

Ray S

That is exactly what was done. The "select group" is internet forum participants (certainly you see how that taints the data). To be a valid sample the group needs to be a random sample of the entire population. Sorry, but a post to a few message boards is not even close.

Furthermore, the respondents were not qualified. In other words anyone on the internet could respond to the survey even if they never owned a Boxster.

You are trying to take a small subset of the population (internet forum participants) and extract meaninful data while ignoring the majority of the population. I'd be willing to bet that the vast majority of Boxster owners have never even heard of Rennlist, PPBB, etc.

Let me put it to you this way, what if you do a poll on Rennlist of the percentage of Porsche owners who "track" their cars. Do you think you would get an accurate percentage on Rennlist vs. what you would find in the entire population of Porsche owners. I think not.

As I said before, garbage in garbage out.

First986NJ

Like Jay said, no point rehashing it ....so I'll concede to the "select group" and "unqualified" points and drop it right here.

986Jim

Sorry didn't mean to beat a dead horse here...

I was just stating that the best way is to enjoy our cars, do as the manual says and if something happens you just fix it, thats it. Worrying about it, wondering when it will happen and will it happen to me scenarios are just asinine.

Macster

emissions vs. engine health/longevity.

While modern fuel injected engines can be driven cold and are relatively well-behaved in these circumstances that doesn't mean they should be treated that way.

Otoh, no need to do as one neighbor used to do: Allow her T-Bird to idle until engine was almost up to operating temperature!.

But a moment or two of idling is not the worst thing you can do for your Boxster's engine.

In the past, I've used the drop of the idle RPMs as "signal" engine has had enough warmup before driving off.

With my Boxster I listen to the air-injection pump. When it shuts off then I drive the car away. This takes even on the colder days less than a minute. By this time idle RPMs have dropped to near normal and engine is quite well-behaved.

With my new GTO, I watch the instantaneous fuel consumption readout in the dash and when it drops below 1.0 gph I'm off.

No matter which car, though I still take it easy until engine/car have had time to reach full operating temperature and this in real cold weather can take 10 miles or more of moderate driving.

Even so, I like to see the temperature gage needle reach the full operating temperature mark and remain there for several minutes just to ensure all engine oil and coolant are indeed up to temperature.

Idling a cold engine until full warmed up is unnecessary, though of course if one needs heat to defrost iced over windows, etc., then idling the engine until the windows are clear is a very good idea.

BTW, my '02 suffered a RMS but I never participated in the engine survey.

Sincerely,

Macster.

gfl

The issue is nto around driveability - its about lubrication related wear and failure.

In very cold weather my car takes 20 min easily before oil is at 100 degC - which is roughly design spec.

Grant

gfl

Not my opinion......

Keeping rpms at a level that cold oil can flow and keep up with seems like a really, really, good idea.

Grant