Maintenance - neccesities vs. money making

I am now a "snow bird" spending winters in a warm area, but until recently, I lived in Indiana year round. While engines would last longer if you change oil at 3000 mile intervals, unless you really drive a lot, what's the point? The road salt will destroy the rest of the car in 15-20 years anyway, so unless you want to use the engine from your rusty hulk to run a generator or something, why not "recycle" the engine with the rest of the car?

Back in 1987 (88? 89?) I had a tour of Chrysler's Trenton Engine facility where the 2.2L/2.2L Turbo were assembled. Our friend's dad was the plant manager at the time, so we got the entire show from soup to nuts. Each and every one was 'hot-tested' before it went on the rack to be shipped. They had a pretty cool system for determining what was wrong with the bad ones that failed the test; the tech would look up on his screen and be able to determine which cylinder, say, hadn't performed up-to-snuff.

Of course, that was a bunch of years ago, now, and I don't know if they still hot-test everything. Maybe as you suggest, the machining techniques of the day mandated this, where today they do not. But it was pretty cool to watch the assembled engine go down the conveyer, disappear into a big boxlike machine, and then fire up and rev to redline for a few seconds before emerging (usually intact) on the other side. They had a special operation at the end of the line to remove the temporary flywheel from the motor and replace it with the one specific to the application for which that engine was intended before it was shipped.

--Geoff

Living in a snowy area is probably another factor GM took into consideration. Why have the engine last a long time if the body won't? It doesn't count for people out west, esp. in the southwest though. The bodies will last for 50 years in the desert areas, then you'll want to change your oil every 3000 miles so you can keep your car a lot longer. But it all goes back to all the factors they were taken into consideration. Waiting longer to change oil DOES wear out the engine faster.

mostly its better OIL. Engine specs (clearances, tolerances, etc.) have hardly changed in 40 years. About the most significant thing is that hypereutectic pistons and short "slipper" pistons are becoming common within the past 3-4 years, but most manufacturers have actually given up a little engine longevity during that change-over. It will recover when they figure out how to mass-produce engines with tolerances required for hypereutectics (I think Chrysler already has it figured out by using coated skirts on the new 5.7 Hemi's engine). But the recent spate of problems with hypereutectics occured for the very reason that there has been no similar change in the necessary tolerances for the previous 40 years!

No, I don't agree. When people have done oil analyses of engine oil at

3000, 4000, 5000, 9000, and even 12,000 miles on the OIL, the analysis results do NOT always indicate that the older oil is causing more metal removal (wear) in the engine at all. Of course it is somewhat dependant on both the engine and the oil, but the general conclusion is that oil doesn't deteriorate NEARLY as fast as it was once ASSumed that it did.

Before you make "scientific" statements based on intuition, go read bobistheoilguy.com

Steve wrote in news:J_mdnf779YECQnzdRVn snipped-for-privacy@texas.net:

Sure, oil may not "deteriorate NEARLY as fast as it once was assumed" but it still deteriotes. Go ahead and wait 12,000 miles between oil changes, you moron. Have fun paying for replacement engines.

So you're scientific? I guess you know more about mechanical wear and tear than countless mechanical engineers who work for auto manufacturers like Chrysler, GM, etc., right hotshot? As you stated yourself, there are many variables: oil used, engine type, type of driving, etc.. It'd be pretty reckless to tell some people they can wait 10,000 miles to get their oil changed when they're hard on their engines and should change their oil every

4000 or less.

Yes and no. There is no magic point where the wear magically accelerates. It depends more on driving habits that oil change intervals. A car that is driven long distances every day might well go

10,000 miles between changes. A car that is driven many short trips a day in stop and go traffic, might need an oil change at 3,000 miles.

Also, most wear occurs during engine start when the oil pressure isn't up to nominal. One of the worse times for this is after an oil change while the filter is being filled and oil is getting circulated back through the engine. I don't have any more data than you have, but it wouldn't surprise me that there is a point where the wear caused from the oil change exceeds that saved by having cleaner oil.

It probably did, but we have no way to know that, unless somebody here works for GM and knows the details first hand.

Matt

Do you have any data that shows how much faster an engine wears out based on different oil change intervals? OK, that is what I thought...

Matt

So you're saying that, say, the piston-to-cylinder factory tolerances and clearances of a '98 (choose your make) are not significantly less than those of a 1962 engine from the same manufacturer? You know more about this stuff than I do, but I'm surprised to hear this.

In my '99 LH vehicle shop manual, I see piston diameter tolerance of 6 tenths with max. clearance at size location of 0.0016". I see similar clearances in my FSM for a '96 Mercury Contour/Ford Contour. How do they compare to 60's engine specs?

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

So, like, did you not know that Steve owns several vehicles with multiple hundreds of thousands of miles on the original engine? Or are you just a moron incapable of comprehending that *testing* the condition of the engine oil is much more accurate and precise than *guessing* or changing it at some arbitrary mileage?

-DS (...or both?)

Owner's manuals aren't written by engineers, mechanical or otherwise.

There is no magic mileage at which it's best to change engine oil. There are two ways to assure proper engine lubrication: Change the oil at a safe interval with essentially zero chance of the oil having deteriorated to an unacceptable level, or send a sample of the oil for detailed analysis at intervals so as to *know* its state of deterioration. The former approach is easier but more expensive in the long run. The latter approach is considerably more scientific.

Right. That's why periodic oil analysis allows you to get a thorough idea of how your chosen oil holds up in your car under your driving conditions.

DS

Been a mechanic since 1972 - apprentice 2 years before that - and have seen engines with oil changed regularly and often, as well as those totally neglected. From my experience the neglected engines lasted about half as long, and contributed significantly more to the profitability of the repair shop than those treated to extra oil changes. In particular, timing chains and tensioners caused SIGNIFICANTLY more problems on the "neglected" vehicles. Particularly on the Mitsu 2.6 engines in Chryslers, and the Toyota 7R, 8R, 18R,and 22R series engines (where timing chain problems were virtually unheard of on an engine serviced by the "B" or severe schedule and very common on those "serviced" with extended drain intervals. On Ford small blocks I never saw an oil pump shaft twist off on a regularly serviced engine - saw lots of them on neglected engines.

Never had a problem with AMC 232 and 258 engines wearing out rocker assemblies on regularly serviced engines, yet replaced MANY on those engines where oil changes were considered "optional". Never had valve train problems on well serviced slant sixes either -or any other mechanical problems. Those with poor oil change records DID wear rocker shafts, and even get squeaky on occaision. Occaisionally lost oil pressure and grenaded too.

Toyotas with spotty oil change histories have had significantly increased incidence of sticky oil rings - and oil consumption, over those serviced according to the "severe" schedule.

Early 230 Chevy sixes were prone to noisy lifters - even at the best of times - and poor oil change frequency made the problem a LOT worse.

When tearing down engines for repair / rebuild, most engines that obviously had few oil changes (lots of gum and sludge) were much more likely to have pitted cam lobes, lifter bores, and bearing journals due to acid etching than clean engines.

Need I go any farther???? Scientific proof?? No. Experience? Yes. I'll take empirical proof over scientific proof any day. It's where the "rubber hits the road" that counts - not the lab.

The "mean" clearances have not changed so much, but the accuracy has. Where in 1962 a bearing clearance SPEC may have been 3 thou, and actual clearance may have varied from .5 to 3.5 due to surface imperfections, today's spec may well be 2.5 thou, and actual clearance may vary from 2.25 to 2.6. The spec can be lower today because, with closer tolerances and better machining, the minimum actual clearance is larger. There is a lot less metal in the breakin oil today than in the past due to this better machining accuracy.

That's what he's saying, and he's right.

I checked '62, '65 and '70 FSMs for the piston-to-cylinder clearance. Each FSM says 0.0005" to 0.0015".

-DS

From evidence you've presented here, you've been a *parts changer* since

1972. It's different.

Red herring. Nobody's recommending neglecting oil changes or any other aspect of engine maintenance.

Changing engine oil according to the results of periodic engine oil analysis does NOT equal neglect, even if the oil analysis shows any particular oil in any particular engine in any particular car being driven in any particular location being suitable for further use at 3,000 miles or 8,000 kilometres or whatever.

There is no magic distance at which any oil in any engine in any car suddenly becomes unserviceable.

DS

Experience is nice, but I've seen lots of anecdotal "evidence" that didn't stand up to a rigorous analysis. Also, it depends on what you mean by neglected. If you mean the oil was never changed, then that is one thing. If you are saying engines with oil changed at 6,000 miles vs. 3,000 miles experienced all of the trouble you list above, then I think you are blowing smoke.

Unfortunately, there have been very few documented experiments with real engines, running in the real world under controlled conditions. One of the few I'm aware of was done several years ago by Consumer Reports. Memory is vague due to the elapsed time, but I think they used conventional oils changed at 6,000 mile intervals and found virtually no wear after 60,000 miles. I think they also had a few cars that received more frequent oil changes and they found no difference between those and the cars with the longer intervals. Now, these tests used taxis which aren't exactly representative of most drivers, but it at least was an attempt at a controlled experiment. If you know of any others, I'd love to hear about them.

I run Mobil 1 and use 5,000 changes only because I'm very confident that this is a very conservative change interval. I'm sure I could run longer if I used oil analysis and did oil changes based on oil condition, but frankly the oil analysis is enough of an expense and nuisance that I just change at 5,000 and don't worry about it. My 96 Grand Voyager has 153K using this regimen and is still going strong. My

89 Acclaim made it over 140K prior to being totaled. I had a Honda Accord that had a serious engine failure at 72,000 miles using Mobil 1 at 5,000 mile intervals. However, there was no indication that it was an oil failure, but more likely a camshaft that wasn't properly heat treated.

Matt

You're being a bit hasty in your judgment. Many cars' trip computers now indicate services/oil changes at intervals way in excess of 10 000 miles.

DAS