Oil change intervals

I don't know which weird part of the world you're hailing from but you can get replacement engines for almost any vehicle on the road easily.

HOwever the likelihood of failure is very low, you've got say a 5% chance of the engine failing due to your normal oil changes versus a 2.5% chance with the improved ones (& that's being optimistic about the improved changes) so you can divide the cost of the engine by 20.

The number of people who buy a new car - so can be sure your maintenance ideas are fully carried out - and keep it for 30 years must be so tiny as to be insignificant.

i remember storys of viper racing n beating motorcycles......might of been 900cc....

I am talking about an exact replica. Just the same engine code is not enough; the new has to be slotted in precisely as the old without needing to cut bits off, modifying to mate without strain with all the ins and outs of the old. The transmission unit and the steering assembly come readily to mind here! Even the mounting placement may be awkward. Take a car as popular as a Mini if you like. I doubt if you could just make a few phone calls and get your exact engine for a mid-1970's model now. After

It used to be that cars were designed to have a service life of 7 years. Now it's 15 years. When the engine fails, it is because it is worn out, parameters of moving parts have exceeded permissible tolerances, and it is uneconomic to overhaul the engine. This end stage can be deferred, and most certainly has been done successfully many times over by caring individuals. The critical deciding factor is whether the engine lubricant has been chosen and used optimally. Car manufacturers in concert with the oil majors have been arbitrary (or flippant) in their instructions(1). It is getting better, at least to the casual observer: on-board evaluation modules are appearing to warn the driver when an oil change is due. But if you want more than 15 years? Tough. "The likelihood of failure is very low"? No, it's prolific taking the industry as a whole statistically; it's the designed end point.

(1) In an average car of average sump capacity, of Normal Service (as against Severe Service, or Extra Severe Service) the modern petroleum oil (as against synthetic oil(2)) needs to be changed after 212 hours of engine *running*. Why are we still advised to change oil after so many miles of *travel*, or more mysteriously, after so many months of

(2) There is some confusion here: regardless of which type of oil is used, whether dino or synthetic, the OCI recommendation does not change, some say.

I'm not quite sure why you'd want to replace the engine. Worn out ones can be overhauled and brought back to often (with older units like a Mini) better than new condition.

Lin Chung ( snipped-for-privacy@the.Water.Margin.com) gurgled happily, sounding much like they were saying :

You really don't have a clue, do you?

A replacement engine for a '70s Mini would be a piece of piss. An A- series is an A-series is an A-series. Sure, there's a few minor changes between (say) a Mini and a Moggy Thou lump, but it'd not be exactly difficult to change sumps and mounts and end up with a 1275 Minor.

Here y'go - the first couple of sites from a Google for "Mini Parts"

I've got an engine out of a '75 Citroen Ami 8 sat in my lockup, if you fancy a bit more power from a 2cv (although it may well end up in my Acadiane van).

Because there's a display in front of you which tells you how many miles you've travelled. Few cars have an engine-hours counter.

Bit more to it surely? The transverse engines have totally different flywheel mountings?

Dave Plowman (News) ( snipped-for-privacy@davenoise.co.uk) gurgled happily, sounding much like they were saying :

Is that something that can't be overcome?

Whatever the detail of the example, the point stands.

Yes.

Actually for mini that'll be a doddle.

Because if you've actually owned a modern car, most of them don't have any significant lubrication related wear at a 150000miles. Almost all the engine failures that turn up on this list have nothing to do with lubrication.

Yes - you fit the correct crankshaft and flywheel. So better to buy the inline version in the first place - plenty around from Marinas, etc.

You could have stuck with Minis - plenty of different sized engines and I'd say any could be fitted reasonably easily to any age.

BMW are often accused of pushing the oil change limits too far, but my last 525 24 valve had over 150,000 miles when sold and only ever had oil changes when the indicator said. The engine was if anything better than new.

Dave Plowman (News) ( snipped-for-privacy@davenoise.co.uk) gurgled happily, sounding much like they were saying :

Furry muff. I don't tend to piss around with old Brit tin, so...

Indeed - however I was extending the point to illustrate that there's great deal of commonality between engines from varying different models, too - the PP picked the Mini, and hence the venerable A-series, but the v8 in your SD1 is also a fine example.

You've missed the point entirely. Whether there is a display showing the mileage travelled is irrelevant.

Quite a few cars have service indicators which compute the condition of the oil and alter the service intervals accordingly. But this level of sophistication doesn't suit the 'every 3000 miles' brigade.

A simple engine hour counter can be fashioned with a small battery-powered portable alarm clock (~£3). The circuit of the power pack is then interrupted with a reed switch. This switch is placed alongside the signal wire from the crankshaft position sensor (OK, it's AC but it may still work; if not, use the Hall effect sensor (DC here) in the distributor, if there is one) to the CPU. When the engine fires up the alarm clock is turned on and runs, and when the engine stops, the clock also stops. Setting the clock at midnight (the long arm and the short arm lined up) to start, the accumulated runs of the clock indicates the total time of engine run. Now at the start of the 10th 'day' the engine would have run a total of 9 x 24h or 216h. Details need to be worked out. Sophistication? No, even I can do it. :)

If I am to implement this, I would change the oil on the 4th 'day', i.e. when the engine has clocked up between 72h and 120h of use. I'm firmly in the Severe Service user category.

Fine, but where do you get your hours run from? Most of the modern systems actually allow for number of cold starts & engine revs.

Vast oversimplification of how service intervals are calculated - they include cold starts, average journey durations etc etc, not just X hours.

And my dads 535i has 180K and inside still looks golden and new. Bearly even soils the oil between changes and never needs topping up.

Ideally all cars would be looked after correctly so the benefit would be passed on to the new owners. I personally keep mine changed regularly simply so when it does fail I know it wasnt my fault and I can just put it down to bad luck. Better safe than sorry!